| 1 | @c -*-texinfo-*- |
| 2 | @c This is part of the GNU Guile Reference Manual. |
| 3 | @c Copyright (C) 1996, 1997, 2000-2004, 2006-2014 |
| 4 | @c Free Software Foundation, Inc. |
| 5 | @c See the file guile.texi for copying conditions. |
| 6 | |
| 7 | @node Simple Data Types |
| 8 | @section Simple Generic Data Types |
| 9 | |
| 10 | This chapter describes those of Guile's simple data types which are |
| 11 | primarily used for their role as items of generic data. By |
| 12 | @dfn{simple} we mean data types that are not primarily used as |
| 13 | containers to hold other data --- i.e.@: pairs, lists, vectors and so on. |
| 14 | For the documentation of such @dfn{compound} data types, see |
| 15 | @ref{Compound Data Types}. |
| 16 | |
| 17 | @c One of the great strengths of Scheme is that there is no straightforward |
| 18 | @c distinction between ``data'' and ``functionality''. For example, |
| 19 | @c Guile's support for dynamic linking could be described: |
| 20 | |
| 21 | @c @itemize @bullet |
| 22 | @c @item |
| 23 | @c either in a ``data-centric'' way, as the behaviour and properties of the |
| 24 | @c ``dynamically linked object'' data type, and the operations that may be |
| 25 | @c applied to instances of this type |
| 26 | |
| 27 | @c @item |
| 28 | @c or in a ``functionality-centric'' way, as the set of procedures that |
| 29 | @c constitute Guile's support for dynamic linking, in the context of the |
| 30 | @c module system. |
| 31 | @c @end itemize |
| 32 | |
| 33 | @c The contents of this chapter are, therefore, a matter of judgment. By |
| 34 | @c @dfn{generic}, we mean to select those data types whose typical use as |
| 35 | @c @emph{data} in a wide variety of programming contexts is more important |
| 36 | @c than their use in the implementation of a particular piece of |
| 37 | @c @emph{functionality}. The last section of this chapter provides |
| 38 | @c references for all the data types that are documented not here but in a |
| 39 | @c ``functionality-centric'' way elsewhere in the manual. |
| 40 | |
| 41 | @menu |
| 42 | * Booleans:: True/false values. |
| 43 | * Numbers:: Numerical data types. |
| 44 | * Characters:: Single characters. |
| 45 | * Character Sets:: Sets of characters. |
| 46 | * Strings:: Sequences of characters. |
| 47 | * Bytevectors:: Sequences of bytes. |
| 48 | * Symbols:: Symbols. |
| 49 | * Keywords:: Self-quoting, customizable display keywords. |
| 50 | * Other Types:: "Functionality-centric" data types. |
| 51 | @end menu |
| 52 | |
| 53 | |
| 54 | @node Booleans |
| 55 | @subsection Booleans |
| 56 | @tpindex Booleans |
| 57 | |
| 58 | The two boolean values are @code{#t} for true and @code{#f} for false. |
| 59 | They can also be written as @code{#true} and @code{#false}, as per R7RS. |
| 60 | |
| 61 | Boolean values are returned by predicate procedures, such as the general |
| 62 | equality predicates @code{eq?}, @code{eqv?} and @code{equal?} |
| 63 | (@pxref{Equality}) and numerical and string comparison operators like |
| 64 | @code{string=?} (@pxref{String Comparison}) and @code{<=} |
| 65 | (@pxref{Comparison}). |
| 66 | |
| 67 | @lisp |
| 68 | (<= 3 8) |
| 69 | @result{} #t |
| 70 | |
| 71 | (<= 3 -3) |
| 72 | @result{} #f |
| 73 | |
| 74 | (equal? "house" "houses") |
| 75 | @result{} #f |
| 76 | |
| 77 | (eq? #f #f) |
| 78 | @result{} |
| 79 | #t |
| 80 | @end lisp |
| 81 | |
| 82 | In test condition contexts like @code{if} and @code{cond} |
| 83 | (@pxref{Conditionals}), where a group of subexpressions will be |
| 84 | evaluated only if a @var{condition} expression evaluates to ``true'', |
| 85 | ``true'' means any value at all except @code{#f}. |
| 86 | |
| 87 | @lisp |
| 88 | (if #t "yes" "no") |
| 89 | @result{} "yes" |
| 90 | |
| 91 | (if 0 "yes" "no") |
| 92 | @result{} "yes" |
| 93 | |
| 94 | (if #f "yes" "no") |
| 95 | @result{} "no" |
| 96 | @end lisp |
| 97 | |
| 98 | A result of this asymmetry is that typical Scheme source code more often |
| 99 | uses @code{#f} explicitly than @code{#t}: @code{#f} is necessary to |
| 100 | represent an @code{if} or @code{cond} false value, whereas @code{#t} is |
| 101 | not necessary to represent an @code{if} or @code{cond} true value. |
| 102 | |
| 103 | It is important to note that @code{#f} is @strong{not} equivalent to any |
| 104 | other Scheme value. In particular, @code{#f} is not the same as the |
| 105 | number 0 (like in C and C++), and not the same as the ``empty list'' |
| 106 | (like in some Lisp dialects). |
| 107 | |
| 108 | In C, the two Scheme boolean values are available as the two constants |
| 109 | @code{SCM_BOOL_T} for @code{#t} and @code{SCM_BOOL_F} for @code{#f}. |
| 110 | Care must be taken with the false value @code{SCM_BOOL_F}: it is not |
| 111 | false when used in C conditionals. In order to test for it, use |
| 112 | @code{scm_is_false} or @code{scm_is_true}. |
| 113 | |
| 114 | @rnindex not |
| 115 | @deffn {Scheme Procedure} not x |
| 116 | @deffnx {C Function} scm_not (x) |
| 117 | Return @code{#t} if @var{x} is @code{#f}, else return @code{#f}. |
| 118 | @end deffn |
| 119 | |
| 120 | @rnindex boolean? |
| 121 | @deffn {Scheme Procedure} boolean? obj |
| 122 | @deffnx {C Function} scm_boolean_p (obj) |
| 123 | Return @code{#t} if @var{obj} is either @code{#t} or @code{#f}, else |
| 124 | return @code{#f}. |
| 125 | @end deffn |
| 126 | |
| 127 | @deftypevr {C Macro} SCM SCM_BOOL_T |
| 128 | The @code{SCM} representation of the Scheme object @code{#t}. |
| 129 | @end deftypevr |
| 130 | |
| 131 | @deftypevr {C Macro} SCM SCM_BOOL_F |
| 132 | The @code{SCM} representation of the Scheme object @code{#f}. |
| 133 | @end deftypevr |
| 134 | |
| 135 | @deftypefn {C Function} int scm_is_true (SCM obj) |
| 136 | Return @code{0} if @var{obj} is @code{#f}, else return @code{1}. |
| 137 | @end deftypefn |
| 138 | |
| 139 | @deftypefn {C Function} int scm_is_false (SCM obj) |
| 140 | Return @code{1} if @var{obj} is @code{#f}, else return @code{0}. |
| 141 | @end deftypefn |
| 142 | |
| 143 | @deftypefn {C Function} int scm_is_bool (SCM obj) |
| 144 | Return @code{1} if @var{obj} is either @code{#t} or @code{#f}, else |
| 145 | return @code{0}. |
| 146 | @end deftypefn |
| 147 | |
| 148 | @deftypefn {C Function} SCM scm_from_bool (int val) |
| 149 | Return @code{#f} if @var{val} is @code{0}, else return @code{#t}. |
| 150 | @end deftypefn |
| 151 | |
| 152 | @deftypefn {C Function} int scm_to_bool (SCM val) |
| 153 | Return @code{1} if @var{val} is @code{SCM_BOOL_T}, return @code{0} |
| 154 | when @var{val} is @code{SCM_BOOL_F}, else signal a `wrong type' error. |
| 155 | |
| 156 | You should probably use @code{scm_is_true} instead of this function |
| 157 | when you just want to test a @code{SCM} value for trueness. |
| 158 | @end deftypefn |
| 159 | |
| 160 | @node Numbers |
| 161 | @subsection Numerical data types |
| 162 | @tpindex Numbers |
| 163 | |
| 164 | Guile supports a rich ``tower'' of numerical types --- integer, |
| 165 | rational, real and complex --- and provides an extensive set of |
| 166 | mathematical and scientific functions for operating on numerical |
| 167 | data. This section of the manual documents those types and functions. |
| 168 | |
| 169 | You may also find it illuminating to read R5RS's presentation of numbers |
| 170 | in Scheme, which is particularly clear and accessible: see |
| 171 | @ref{Numbers,,,r5rs,R5RS}. |
| 172 | |
| 173 | @menu |
| 174 | * Numerical Tower:: Scheme's numerical "tower". |
| 175 | * Integers:: Whole numbers. |
| 176 | * Reals and Rationals:: Real and rational numbers. |
| 177 | * Complex Numbers:: Complex numbers. |
| 178 | * Exactness:: Exactness and inexactness. |
| 179 | * Number Syntax:: Read syntax for numerical data. |
| 180 | * Integer Operations:: Operations on integer values. |
| 181 | * Comparison:: Comparison predicates. |
| 182 | * Conversion:: Converting numbers to and from strings. |
| 183 | * Complex:: Complex number operations. |
| 184 | * Arithmetic:: Arithmetic functions. |
| 185 | * Scientific:: Scientific functions. |
| 186 | * Bitwise Operations:: Logical AND, OR, NOT, and so on. |
| 187 | * Random:: Random number generation. |
| 188 | @end menu |
| 189 | |
| 190 | |
| 191 | @node Numerical Tower |
| 192 | @subsubsection Scheme's Numerical ``Tower'' |
| 193 | @rnindex number? |
| 194 | |
| 195 | Scheme's numerical ``tower'' consists of the following categories of |
| 196 | numbers: |
| 197 | |
| 198 | @table @dfn |
| 199 | @item integers |
| 200 | Whole numbers, positive or negative; e.g.@: --5, 0, 18. |
| 201 | |
| 202 | @item rationals |
| 203 | The set of numbers that can be expressed as @math{@var{p}/@var{q}} |
| 204 | where @var{p} and @var{q} are integers; e.g.@: @math{9/16} works, but |
| 205 | pi (an irrational number) doesn't. These include integers |
| 206 | (@math{@var{n}/1}). |
| 207 | |
| 208 | @item real numbers |
| 209 | The set of numbers that describes all possible positions along a |
| 210 | one-dimensional line. This includes rationals as well as irrational |
| 211 | numbers. |
| 212 | |
| 213 | @item complex numbers |
| 214 | The set of numbers that describes all possible positions in a two |
| 215 | dimensional space. This includes real as well as imaginary numbers |
| 216 | (@math{@var{a}+@var{b}i}, where @var{a} is the @dfn{real part}, |
| 217 | @var{b} is the @dfn{imaginary part}, and @math{i} is the square root of |
| 218 | @minus{}1.) |
| 219 | @end table |
| 220 | |
| 221 | It is called a tower because each category ``sits on'' the one that |
| 222 | follows it, in the sense that every integer is also a rational, every |
| 223 | rational is also real, and every real number is also a complex number |
| 224 | (but with zero imaginary part). |
| 225 | |
| 226 | In addition to the classification into integers, rationals, reals and |
| 227 | complex numbers, Scheme also distinguishes between whether a number is |
| 228 | represented exactly or not. For example, the result of |
| 229 | @m{2\sin(\pi/4),2*sin(pi/4)} is exactly @m{\sqrt{2},2^(1/2)}, but Guile |
| 230 | can represent neither @m{\pi/4,pi/4} nor @m{\sqrt{2},2^(1/2)} exactly. |
| 231 | Instead, it stores an inexact approximation, using the C type |
| 232 | @code{double}. |
| 233 | |
| 234 | Guile can represent exact rationals of any magnitude, inexact |
| 235 | rationals that fit into a C @code{double}, and inexact complex numbers |
| 236 | with @code{double} real and imaginary parts. |
| 237 | |
| 238 | The @code{number?} predicate may be applied to any Scheme value to |
| 239 | discover whether the value is any of the supported numerical types. |
| 240 | |
| 241 | @deffn {Scheme Procedure} number? obj |
| 242 | @deffnx {C Function} scm_number_p (obj) |
| 243 | Return @code{#t} if @var{obj} is any kind of number, else @code{#f}. |
| 244 | @end deffn |
| 245 | |
| 246 | For example: |
| 247 | |
| 248 | @lisp |
| 249 | (number? 3) |
| 250 | @result{} #t |
| 251 | |
| 252 | (number? "hello there!") |
| 253 | @result{} #f |
| 254 | |
| 255 | (define pi 3.141592654) |
| 256 | (number? pi) |
| 257 | @result{} #t |
| 258 | @end lisp |
| 259 | |
| 260 | @deftypefn {C Function} int scm_is_number (SCM obj) |
| 261 | This is equivalent to @code{scm_is_true (scm_number_p (obj))}. |
| 262 | @end deftypefn |
| 263 | |
| 264 | The next few subsections document each of Guile's numerical data types |
| 265 | in detail. |
| 266 | |
| 267 | @node Integers |
| 268 | @subsubsection Integers |
| 269 | |
| 270 | @tpindex Integer numbers |
| 271 | |
| 272 | @rnindex integer? |
| 273 | |
| 274 | Integers are whole numbers, that is numbers with no fractional part, |
| 275 | such as 2, 83, and @minus{}3789. |
| 276 | |
| 277 | Integers in Guile can be arbitrarily big, as shown by the following |
| 278 | example. |
| 279 | |
| 280 | @lisp |
| 281 | (define (factorial n) |
| 282 | (let loop ((n n) (product 1)) |
| 283 | (if (= n 0) |
| 284 | product |
| 285 | (loop (- n 1) (* product n))))) |
| 286 | |
| 287 | (factorial 3) |
| 288 | @result{} 6 |
| 289 | |
| 290 | (factorial 20) |
| 291 | @result{} 2432902008176640000 |
| 292 | |
| 293 | (- (factorial 45)) |
| 294 | @result{} -119622220865480194561963161495657715064383733760000000000 |
| 295 | @end lisp |
| 296 | |
| 297 | Readers whose background is in programming languages where integers are |
| 298 | limited by the need to fit into just 4 or 8 bytes of memory may find |
| 299 | this surprising, or suspect that Guile's representation of integers is |
| 300 | inefficient. In fact, Guile achieves a near optimal balance of |
| 301 | convenience and efficiency by using the host computer's native |
| 302 | representation of integers where possible, and a more general |
| 303 | representation where the required number does not fit in the native |
| 304 | form. Conversion between these two representations is automatic and |
| 305 | completely invisible to the Scheme level programmer. |
| 306 | |
| 307 | C has a host of different integer types, and Guile offers a host of |
| 308 | functions to convert between them and the @code{SCM} representation. |
| 309 | For example, a C @code{int} can be handled with @code{scm_to_int} and |
| 310 | @code{scm_from_int}. Guile also defines a few C integer types of its |
| 311 | own, to help with differences between systems. |
| 312 | |
| 313 | C integer types that are not covered can be handled with the generic |
| 314 | @code{scm_to_signed_integer} and @code{scm_from_signed_integer} for |
| 315 | signed types, or with @code{scm_to_unsigned_integer} and |
| 316 | @code{scm_from_unsigned_integer} for unsigned types. |
| 317 | |
| 318 | Scheme integers can be exact and inexact. For example, a number |
| 319 | written as @code{3.0} with an explicit decimal-point is inexact, but |
| 320 | it is also an integer. The functions @code{integer?} and |
| 321 | @code{scm_is_integer} report true for such a number, but the functions |
| 322 | @code{exact-integer?}, @code{scm_is_exact_integer}, |
| 323 | @code{scm_is_signed_integer}, and @code{scm_is_unsigned_integer} only |
| 324 | allow exact integers and thus report false. Likewise, the conversion |
| 325 | functions like @code{scm_to_signed_integer} only accept exact |
| 326 | integers. |
| 327 | |
| 328 | The motivation for this behavior is that the inexactness of a number |
| 329 | should not be lost silently. If you want to allow inexact integers, |
| 330 | you can explicitly insert a call to @code{inexact->exact} or to its C |
| 331 | equivalent @code{scm_inexact_to_exact}. (Only inexact integers will |
| 332 | be converted by this call into exact integers; inexact non-integers |
| 333 | will become exact fractions.) |
| 334 | |
| 335 | @deffn {Scheme Procedure} integer? x |
| 336 | @deffnx {C Function} scm_integer_p (x) |
| 337 | Return @code{#t} if @var{x} is an exact or inexact integer number, else |
| 338 | return @code{#f}. |
| 339 | |
| 340 | @lisp |
| 341 | (integer? 487) |
| 342 | @result{} #t |
| 343 | |
| 344 | (integer? 3.0) |
| 345 | @result{} #t |
| 346 | |
| 347 | (integer? -3.4) |
| 348 | @result{} #f |
| 349 | |
| 350 | (integer? +inf.0) |
| 351 | @result{} #f |
| 352 | @end lisp |
| 353 | @end deffn |
| 354 | |
| 355 | @deftypefn {C Function} int scm_is_integer (SCM x) |
| 356 | This is equivalent to @code{scm_is_true (scm_integer_p (x))}. |
| 357 | @end deftypefn |
| 358 | |
| 359 | @deffn {Scheme Procedure} exact-integer? x |
| 360 | @deffnx {C Function} scm_exact_integer_p (x) |
| 361 | Return @code{#t} if @var{x} is an exact integer number, else |
| 362 | return @code{#f}. |
| 363 | |
| 364 | @lisp |
| 365 | (exact-integer? 37) |
| 366 | @result{} #t |
| 367 | |
| 368 | (exact-integer? 3.0) |
| 369 | @result{} #f |
| 370 | @end lisp |
| 371 | @end deffn |
| 372 | |
| 373 | @deftypefn {C Function} int scm_is_exact_integer (SCM x) |
| 374 | This is equivalent to @code{scm_is_true (scm_exact_integer_p (x))}. |
| 375 | @end deftypefn |
| 376 | |
| 377 | @defvr {C Type} scm_t_int8 |
| 378 | @defvrx {C Type} scm_t_uint8 |
| 379 | @defvrx {C Type} scm_t_int16 |
| 380 | @defvrx {C Type} scm_t_uint16 |
| 381 | @defvrx {C Type} scm_t_int32 |
| 382 | @defvrx {C Type} scm_t_uint32 |
| 383 | @defvrx {C Type} scm_t_int64 |
| 384 | @defvrx {C Type} scm_t_uint64 |
| 385 | @defvrx {C Type} scm_t_intmax |
| 386 | @defvrx {C Type} scm_t_uintmax |
| 387 | The C types are equivalent to the corresponding ISO C types but are |
| 388 | defined on all platforms, with the exception of @code{scm_t_int64} and |
| 389 | @code{scm_t_uint64}, which are only defined when a 64-bit type is |
| 390 | available. For example, @code{scm_t_int8} is equivalent to |
| 391 | @code{int8_t}. |
| 392 | |
| 393 | You can regard these definitions as a stop-gap measure until all |
| 394 | platforms provide these types. If you know that all the platforms |
| 395 | that you are interested in already provide these types, it is better |
| 396 | to use them directly instead of the types provided by Guile. |
| 397 | @end defvr |
| 398 | |
| 399 | @deftypefn {C Function} int scm_is_signed_integer (SCM x, scm_t_intmax min, scm_t_intmax max) |
| 400 | @deftypefnx {C Function} int scm_is_unsigned_integer (SCM x, scm_t_uintmax min, scm_t_uintmax max) |
| 401 | Return @code{1} when @var{x} represents an exact integer that is |
| 402 | between @var{min} and @var{max}, inclusive. |
| 403 | |
| 404 | These functions can be used to check whether a @code{SCM} value will |
| 405 | fit into a given range, such as the range of a given C integer type. |
| 406 | If you just want to convert a @code{SCM} value to a given C integer |
| 407 | type, use one of the conversion functions directly. |
| 408 | @end deftypefn |
| 409 | |
| 410 | @deftypefn {C Function} scm_t_intmax scm_to_signed_integer (SCM x, scm_t_intmax min, scm_t_intmax max) |
| 411 | @deftypefnx {C Function} scm_t_uintmax scm_to_unsigned_integer (SCM x, scm_t_uintmax min, scm_t_uintmax max) |
| 412 | When @var{x} represents an exact integer that is between @var{min} and |
| 413 | @var{max} inclusive, return that integer. Else signal an error, |
| 414 | either a `wrong-type' error when @var{x} is not an exact integer, or |
| 415 | an `out-of-range' error when it doesn't fit the given range. |
| 416 | @end deftypefn |
| 417 | |
| 418 | @deftypefn {C Function} SCM scm_from_signed_integer (scm_t_intmax x) |
| 419 | @deftypefnx {C Function} SCM scm_from_unsigned_integer (scm_t_uintmax x) |
| 420 | Return the @code{SCM} value that represents the integer @var{x}. This |
| 421 | function will always succeed and will always return an exact number. |
| 422 | @end deftypefn |
| 423 | |
| 424 | @deftypefn {C Function} char scm_to_char (SCM x) |
| 425 | @deftypefnx {C Function} {signed char} scm_to_schar (SCM x) |
| 426 | @deftypefnx {C Function} {unsigned char} scm_to_uchar (SCM x) |
| 427 | @deftypefnx {C Function} short scm_to_short (SCM x) |
| 428 | @deftypefnx {C Function} {unsigned short} scm_to_ushort (SCM x) |
| 429 | @deftypefnx {C Function} int scm_to_int (SCM x) |
| 430 | @deftypefnx {C Function} {unsigned int} scm_to_uint (SCM x) |
| 431 | @deftypefnx {C Function} long scm_to_long (SCM x) |
| 432 | @deftypefnx {C Function} {unsigned long} scm_to_ulong (SCM x) |
| 433 | @deftypefnx {C Function} {long long} scm_to_long_long (SCM x) |
| 434 | @deftypefnx {C Function} {unsigned long long} scm_to_ulong_long (SCM x) |
| 435 | @deftypefnx {C Function} size_t scm_to_size_t (SCM x) |
| 436 | @deftypefnx {C Function} ssize_t scm_to_ssize_t (SCM x) |
| 437 | @deftypefnx {C Function} scm_t_ptrdiff scm_to_ptrdiff_t (SCM x) |
| 438 | @deftypefnx {C Function} scm_t_int8 scm_to_int8 (SCM x) |
| 439 | @deftypefnx {C Function} scm_t_uint8 scm_to_uint8 (SCM x) |
| 440 | @deftypefnx {C Function} scm_t_int16 scm_to_int16 (SCM x) |
| 441 | @deftypefnx {C Function} scm_t_uint16 scm_to_uint16 (SCM x) |
| 442 | @deftypefnx {C Function} scm_t_int32 scm_to_int32 (SCM x) |
| 443 | @deftypefnx {C Function} scm_t_uint32 scm_to_uint32 (SCM x) |
| 444 | @deftypefnx {C Function} scm_t_int64 scm_to_int64 (SCM x) |
| 445 | @deftypefnx {C Function} scm_t_uint64 scm_to_uint64 (SCM x) |
| 446 | @deftypefnx {C Function} scm_t_intmax scm_to_intmax (SCM x) |
| 447 | @deftypefnx {C Function} scm_t_uintmax scm_to_uintmax (SCM x) |
| 448 | @deftypefnx {C Function} scm_t_intptr scm_to_intptr_t (SCM x) |
| 449 | @deftypefnx {C Function} scm_t_uintptr scm_to_uintptr_t (SCM x) |
| 450 | When @var{x} represents an exact integer that fits into the indicated |
| 451 | C type, return that integer. Else signal an error, either a |
| 452 | `wrong-type' error when @var{x} is not an exact integer, or an |
| 453 | `out-of-range' error when it doesn't fit the given range. |
| 454 | |
| 455 | The functions @code{scm_to_long_long}, @code{scm_to_ulong_long}, |
| 456 | @code{scm_to_int64}, and @code{scm_to_uint64} are only available when |
| 457 | the corresponding types are. |
| 458 | @end deftypefn |
| 459 | |
| 460 | @deftypefn {C Function} SCM scm_from_char (char x) |
| 461 | @deftypefnx {C Function} SCM scm_from_schar (signed char x) |
| 462 | @deftypefnx {C Function} SCM scm_from_uchar (unsigned char x) |
| 463 | @deftypefnx {C Function} SCM scm_from_short (short x) |
| 464 | @deftypefnx {C Function} SCM scm_from_ushort (unsigned short x) |
| 465 | @deftypefnx {C Function} SCM scm_from_int (int x) |
| 466 | @deftypefnx {C Function} SCM scm_from_uint (unsigned int x) |
| 467 | @deftypefnx {C Function} SCM scm_from_long (long x) |
| 468 | @deftypefnx {C Function} SCM scm_from_ulong (unsigned long x) |
| 469 | @deftypefnx {C Function} SCM scm_from_long_long (long long x) |
| 470 | @deftypefnx {C Function} SCM scm_from_ulong_long (unsigned long long x) |
| 471 | @deftypefnx {C Function} SCM scm_from_size_t (size_t x) |
| 472 | @deftypefnx {C Function} SCM scm_from_ssize_t (ssize_t x) |
| 473 | @deftypefnx {C Function} SCM scm_from_ptrdiff_t (scm_t_ptrdiff x) |
| 474 | @deftypefnx {C Function} SCM scm_from_int8 (scm_t_int8 x) |
| 475 | @deftypefnx {C Function} SCM scm_from_uint8 (scm_t_uint8 x) |
| 476 | @deftypefnx {C Function} SCM scm_from_int16 (scm_t_int16 x) |
| 477 | @deftypefnx {C Function} SCM scm_from_uint16 (scm_t_uint16 x) |
| 478 | @deftypefnx {C Function} SCM scm_from_int32 (scm_t_int32 x) |
| 479 | @deftypefnx {C Function} SCM scm_from_uint32 (scm_t_uint32 x) |
| 480 | @deftypefnx {C Function} SCM scm_from_int64 (scm_t_int64 x) |
| 481 | @deftypefnx {C Function} SCM scm_from_uint64 (scm_t_uint64 x) |
| 482 | @deftypefnx {C Function} SCM scm_from_intmax (scm_t_intmax x) |
| 483 | @deftypefnx {C Function} SCM scm_from_uintmax (scm_t_uintmax x) |
| 484 | @deftypefnx {C Function} SCM scm_from_intptr_t (scm_t_intptr x) |
| 485 | @deftypefnx {C Function} SCM scm_from_uintptr_t (scm_t_uintptr x) |
| 486 | Return the @code{SCM} value that represents the integer @var{x}. |
| 487 | These functions will always succeed and will always return an exact |
| 488 | number. |
| 489 | @end deftypefn |
| 490 | |
| 491 | @deftypefn {C Function} void scm_to_mpz (SCM val, mpz_t rop) |
| 492 | Assign @var{val} to the multiple precision integer @var{rop}. |
| 493 | @var{val} must be an exact integer, otherwise an error will be |
| 494 | signalled. @var{rop} must have been initialized with @code{mpz_init} |
| 495 | before this function is called. When @var{rop} is no longer needed |
| 496 | the occupied space must be freed with @code{mpz_clear}. |
| 497 | @xref{Initializing Integers,,, gmp, GNU MP Manual}, for details. |
| 498 | @end deftypefn |
| 499 | |
| 500 | @deftypefn {C Function} SCM scm_from_mpz (mpz_t val) |
| 501 | Return the @code{SCM} value that represents @var{val}. |
| 502 | @end deftypefn |
| 503 | |
| 504 | @node Reals and Rationals |
| 505 | @subsubsection Real and Rational Numbers |
| 506 | @tpindex Real numbers |
| 507 | @tpindex Rational numbers |
| 508 | |
| 509 | @rnindex real? |
| 510 | @rnindex rational? |
| 511 | |
| 512 | Mathematically, the real numbers are the set of numbers that describe |
| 513 | all possible points along a continuous, infinite, one-dimensional line. |
| 514 | The rational numbers are the set of all numbers that can be written as |
| 515 | fractions @var{p}/@var{q}, where @var{p} and @var{q} are integers. |
| 516 | All rational numbers are also real, but there are real numbers that |
| 517 | are not rational, for example @m{\sqrt{2}, the square root of 2}, and |
| 518 | @m{\pi,pi}. |
| 519 | |
| 520 | Guile can represent both exact and inexact rational numbers, but it |
| 521 | cannot represent precise finite irrational numbers. Exact rationals are |
| 522 | represented by storing the numerator and denominator as two exact |
| 523 | integers. Inexact rationals are stored as floating point numbers using |
| 524 | the C type @code{double}. |
| 525 | |
| 526 | Exact rationals are written as a fraction of integers. There must be |
| 527 | no whitespace around the slash: |
| 528 | |
| 529 | @lisp |
| 530 | 1/2 |
| 531 | -22/7 |
| 532 | @end lisp |
| 533 | |
| 534 | Even though the actual encoding of inexact rationals is in binary, it |
| 535 | may be helpful to think of it as a decimal number with a limited |
| 536 | number of significant figures and a decimal point somewhere, since |
| 537 | this corresponds to the standard notation for non-whole numbers. For |
| 538 | example: |
| 539 | |
| 540 | @lisp |
| 541 | 0.34 |
| 542 | -0.00000142857931198 |
| 543 | -5648394822220000000000.0 |
| 544 | 4.0 |
| 545 | @end lisp |
| 546 | |
| 547 | The limited precision of Guile's encoding means that any finite ``real'' |
| 548 | number in Guile can be written in a rational form, by multiplying and |
| 549 | then dividing by sufficient powers of 10 (or in fact, 2). For example, |
| 550 | @samp{-0.00000142857931198} is the same as @minus{}142857931198 divided |
| 551 | by 100000000000000000. In Guile's current incarnation, therefore, the |
| 552 | @code{rational?} and @code{real?} predicates are equivalent for finite |
| 553 | numbers. |
| 554 | |
| 555 | |
| 556 | Dividing by an exact zero leads to a error message, as one might expect. |
| 557 | However, dividing by an inexact zero does not produce an error. |
| 558 | Instead, the result of the division is either plus or minus infinity, |
| 559 | depending on the sign of the divided number and the sign of the zero |
| 560 | divisor (some platforms support signed zeroes @samp{-0.0} and |
| 561 | @samp{+0.0}; @samp{0.0} is the same as @samp{+0.0}). |
| 562 | |
| 563 | Dividing zero by an inexact zero yields a @acronym{NaN} (`not a number') |
| 564 | value, although they are actually considered numbers by Scheme. |
| 565 | Attempts to compare a @acronym{NaN} value with any number (including |
| 566 | itself) using @code{=}, @code{<}, @code{>}, @code{<=} or @code{>=} |
| 567 | always returns @code{#f}. Although a @acronym{NaN} value is not |
| 568 | @code{=} to itself, it is both @code{eqv?} and @code{equal?} to itself |
| 569 | and other @acronym{NaN} values. However, the preferred way to test for |
| 570 | them is by using @code{nan?}. |
| 571 | |
| 572 | The real @acronym{NaN} values and infinities are written @samp{+nan.0}, |
| 573 | @samp{+inf.0} and @samp{-inf.0}. This syntax is also recognized by |
| 574 | @code{read} as an extension to the usual Scheme syntax. These special |
| 575 | values are considered by Scheme to be inexact real numbers but not |
| 576 | rational. Note that non-real complex numbers may also contain |
| 577 | infinities or @acronym{NaN} values in their real or imaginary parts. To |
| 578 | test a real number to see if it is infinite, a @acronym{NaN} value, or |
| 579 | neither, use @code{inf?}, @code{nan?}, or @code{finite?}, respectively. |
| 580 | Every real number in Scheme belongs to precisely one of those three |
| 581 | classes. |
| 582 | |
| 583 | On platforms that follow @acronym{IEEE} 754 for their floating point |
| 584 | arithmetic, the @samp{+inf.0}, @samp{-inf.0}, and @samp{+nan.0} values |
| 585 | are implemented using the corresponding @acronym{IEEE} 754 values. |
| 586 | They behave in arithmetic operations like @acronym{IEEE} 754 describes |
| 587 | it, i.e., @code{(= +nan.0 +nan.0)} @result{} @code{#f}. |
| 588 | |
| 589 | @deffn {Scheme Procedure} real? obj |
| 590 | @deffnx {C Function} scm_real_p (obj) |
| 591 | Return @code{#t} if @var{obj} is a real number, else @code{#f}. Note |
| 592 | that the sets of integer and rational values form subsets of the set |
| 593 | of real numbers, so the predicate will also be fulfilled if @var{obj} |
| 594 | is an integer number or a rational number. |
| 595 | @end deffn |
| 596 | |
| 597 | @deffn {Scheme Procedure} rational? x |
| 598 | @deffnx {C Function} scm_rational_p (x) |
| 599 | Return @code{#t} if @var{x} is a rational number, @code{#f} otherwise. |
| 600 | Note that the set of integer values forms a subset of the set of |
| 601 | rational numbers, i.e.@: the predicate will also be fulfilled if |
| 602 | @var{x} is an integer number. |
| 603 | @end deffn |
| 604 | |
| 605 | @deffn {Scheme Procedure} rationalize x eps |
| 606 | @deffnx {C Function} scm_rationalize (x, eps) |
| 607 | Returns the @emph{simplest} rational number differing |
| 608 | from @var{x} by no more than @var{eps}. |
| 609 | |
| 610 | As required by @acronym{R5RS}, @code{rationalize} only returns an |
| 611 | exact result when both its arguments are exact. Thus, you might need |
| 612 | to use @code{inexact->exact} on the arguments. |
| 613 | |
| 614 | @lisp |
| 615 | (rationalize (inexact->exact 1.2) 1/100) |
| 616 | @result{} 6/5 |
| 617 | @end lisp |
| 618 | |
| 619 | @end deffn |
| 620 | |
| 621 | @deffn {Scheme Procedure} inf? x |
| 622 | @deffnx {C Function} scm_inf_p (x) |
| 623 | Return @code{#t} if the real number @var{x} is @samp{+inf.0} or |
| 624 | @samp{-inf.0}. Otherwise return @code{#f}. |
| 625 | @end deffn |
| 626 | |
| 627 | @deffn {Scheme Procedure} nan? x |
| 628 | @deffnx {C Function} scm_nan_p (x) |
| 629 | Return @code{#t} if the real number @var{x} is @samp{+nan.0}, or |
| 630 | @code{#f} otherwise. |
| 631 | @end deffn |
| 632 | |
| 633 | @deffn {Scheme Procedure} finite? x |
| 634 | @deffnx {C Function} scm_finite_p (x) |
| 635 | Return @code{#t} if the real number @var{x} is neither infinite nor a |
| 636 | NaN, @code{#f} otherwise. |
| 637 | @end deffn |
| 638 | |
| 639 | @deffn {Scheme Procedure} nan |
| 640 | @deffnx {C Function} scm_nan () |
| 641 | Return @samp{+nan.0}, a @acronym{NaN} value. |
| 642 | @end deffn |
| 643 | |
| 644 | @deffn {Scheme Procedure} inf |
| 645 | @deffnx {C Function} scm_inf () |
| 646 | Return @samp{+inf.0}, positive infinity. |
| 647 | @end deffn |
| 648 | |
| 649 | @deffn {Scheme Procedure} numerator x |
| 650 | @deffnx {C Function} scm_numerator (x) |
| 651 | Return the numerator of the rational number @var{x}. |
| 652 | @end deffn |
| 653 | |
| 654 | @deffn {Scheme Procedure} denominator x |
| 655 | @deffnx {C Function} scm_denominator (x) |
| 656 | Return the denominator of the rational number @var{x}. |
| 657 | @end deffn |
| 658 | |
| 659 | @deftypefn {C Function} int scm_is_real (SCM val) |
| 660 | @deftypefnx {C Function} int scm_is_rational (SCM val) |
| 661 | Equivalent to @code{scm_is_true (scm_real_p (val))} and |
| 662 | @code{scm_is_true (scm_rational_p (val))}, respectively. |
| 663 | @end deftypefn |
| 664 | |
| 665 | @deftypefn {C Function} double scm_to_double (SCM val) |
| 666 | Returns the number closest to @var{val} that is representable as a |
| 667 | @code{double}. Returns infinity for a @var{val} that is too large in |
| 668 | magnitude. The argument @var{val} must be a real number. |
| 669 | @end deftypefn |
| 670 | |
| 671 | @deftypefn {C Function} SCM scm_from_double (double val) |
| 672 | Return the @code{SCM} value that represents @var{val}. The returned |
| 673 | value is inexact according to the predicate @code{inexact?}, but it |
| 674 | will be exactly equal to @var{val}. |
| 675 | @end deftypefn |
| 676 | |
| 677 | @node Complex Numbers |
| 678 | @subsubsection Complex Numbers |
| 679 | @tpindex Complex numbers |
| 680 | |
| 681 | @rnindex complex? |
| 682 | |
| 683 | Complex numbers are the set of numbers that describe all possible points |
| 684 | in a two-dimensional space. The two coordinates of a particular point |
| 685 | in this space are known as the @dfn{real} and @dfn{imaginary} parts of |
| 686 | the complex number that describes that point. |
| 687 | |
| 688 | In Guile, complex numbers are written in rectangular form as the sum of |
| 689 | their real and imaginary parts, using the symbol @code{i} to indicate |
| 690 | the imaginary part. |
| 691 | |
| 692 | @lisp |
| 693 | 3+4i |
| 694 | @result{} |
| 695 | 3.0+4.0i |
| 696 | |
| 697 | (* 3-8i 2.3+0.3i) |
| 698 | @result{} |
| 699 | 9.3-17.5i |
| 700 | @end lisp |
| 701 | |
| 702 | @cindex polar form |
| 703 | @noindent |
| 704 | Polar form can also be used, with an @samp{@@} between magnitude and |
| 705 | angle, |
| 706 | |
| 707 | @lisp |
| 708 | 1@@3.141592 @result{} -1.0 (approx) |
| 709 | -1@@1.57079 @result{} 0.0-1.0i (approx) |
| 710 | @end lisp |
| 711 | |
| 712 | Guile represents a complex number as a pair of inexact reals, so the |
| 713 | real and imaginary parts of a complex number have the same properties of |
| 714 | inexactness and limited precision as single inexact real numbers. |
| 715 | |
| 716 | Note that each part of a complex number may contain any inexact real |
| 717 | value, including the special values @samp{+nan.0}, @samp{+inf.0} and |
| 718 | @samp{-inf.0}, as well as either of the signed zeroes @samp{0.0} or |
| 719 | @samp{-0.0}. |
| 720 | |
| 721 | |
| 722 | @deffn {Scheme Procedure} complex? z |
| 723 | @deffnx {C Function} scm_complex_p (z) |
| 724 | Return @code{#t} if @var{z} is a complex number, @code{#f} |
| 725 | otherwise. Note that the sets of real, rational and integer |
| 726 | values form subsets of the set of complex numbers, i.e.@: the |
| 727 | predicate will also be fulfilled if @var{z} is a real, |
| 728 | rational or integer number. |
| 729 | @end deffn |
| 730 | |
| 731 | @deftypefn {C Function} int scm_is_complex (SCM val) |
| 732 | Equivalent to @code{scm_is_true (scm_complex_p (val))}. |
| 733 | @end deftypefn |
| 734 | |
| 735 | @node Exactness |
| 736 | @subsubsection Exact and Inexact Numbers |
| 737 | @tpindex Exact numbers |
| 738 | @tpindex Inexact numbers |
| 739 | |
| 740 | @rnindex exact? |
| 741 | @rnindex inexact? |
| 742 | @rnindex exact->inexact |
| 743 | @rnindex inexact->exact |
| 744 | |
| 745 | R5RS requires that, with few exceptions, a calculation involving inexact |
| 746 | numbers always produces an inexact result. To meet this requirement, |
| 747 | Guile distinguishes between an exact integer value such as @samp{5} and |
| 748 | the corresponding inexact integer value which, to the limited precision |
| 749 | available, has no fractional part, and is printed as @samp{5.0}. Guile |
| 750 | will only convert the latter value to the former when forced to do so by |
| 751 | an invocation of the @code{inexact->exact} procedure. |
| 752 | |
| 753 | The only exception to the above requirement is when the values of the |
| 754 | inexact numbers do not affect the result. For example @code{(expt n 0)} |
| 755 | is @samp{1} for any value of @code{n}, therefore @code{(expt 5.0 0)} is |
| 756 | permitted to return an exact @samp{1}. |
| 757 | |
| 758 | @deffn {Scheme Procedure} exact? z |
| 759 | @deffnx {C Function} scm_exact_p (z) |
| 760 | Return @code{#t} if the number @var{z} is exact, @code{#f} |
| 761 | otherwise. |
| 762 | |
| 763 | @lisp |
| 764 | (exact? 2) |
| 765 | @result{} #t |
| 766 | |
| 767 | (exact? 0.5) |
| 768 | @result{} #f |
| 769 | |
| 770 | (exact? (/ 2)) |
| 771 | @result{} #t |
| 772 | @end lisp |
| 773 | |
| 774 | @end deffn |
| 775 | |
| 776 | @deftypefn {C Function} int scm_is_exact (SCM z) |
| 777 | Return a @code{1} if the number @var{z} is exact, and @code{0} |
| 778 | otherwise. This is equivalent to @code{scm_is_true (scm_exact_p (z))}. |
| 779 | |
| 780 | An alternate approch to testing the exactness of a number is to |
| 781 | use @code{scm_is_signed_integer} or @code{scm_is_unsigned_integer}. |
| 782 | @end deftypefn |
| 783 | |
| 784 | @deffn {Scheme Procedure} inexact? z |
| 785 | @deffnx {C Function} scm_inexact_p (z) |
| 786 | Return @code{#t} if the number @var{z} is inexact, @code{#f} |
| 787 | else. |
| 788 | @end deffn |
| 789 | |
| 790 | @deftypefn {C Function} int scm_is_inexact (SCM z) |
| 791 | Return a @code{1} if the number @var{z} is inexact, and @code{0} |
| 792 | otherwise. This is equivalent to @code{scm_is_true (scm_inexact_p (z))}. |
| 793 | @end deftypefn |
| 794 | |
| 795 | @deffn {Scheme Procedure} inexact->exact z |
| 796 | @deffnx {C Function} scm_inexact_to_exact (z) |
| 797 | Return an exact number that is numerically closest to @var{z}, when |
| 798 | there is one. For inexact rationals, Guile returns the exact rational |
| 799 | that is numerically equal to the inexact rational. Inexact complex |
| 800 | numbers with a non-zero imaginary part can not be made exact. |
| 801 | |
| 802 | @lisp |
| 803 | (inexact->exact 0.5) |
| 804 | @result{} 1/2 |
| 805 | @end lisp |
| 806 | |
| 807 | The following happens because 12/10 is not exactly representable as a |
| 808 | @code{double} (on most platforms). However, when reading a decimal |
| 809 | number that has been marked exact with the ``#e'' prefix, Guile is |
| 810 | able to represent it correctly. |
| 811 | |
| 812 | @lisp |
| 813 | (inexact->exact 1.2) |
| 814 | @result{} 5404319552844595/4503599627370496 |
| 815 | |
| 816 | #e1.2 |
| 817 | @result{} 6/5 |
| 818 | @end lisp |
| 819 | |
| 820 | @end deffn |
| 821 | |
| 822 | @c begin (texi-doc-string "guile" "exact->inexact") |
| 823 | @deffn {Scheme Procedure} exact->inexact z |
| 824 | @deffnx {C Function} scm_exact_to_inexact (z) |
| 825 | Convert the number @var{z} to its inexact representation. |
| 826 | @end deffn |
| 827 | |
| 828 | |
| 829 | @node Number Syntax |
| 830 | @subsubsection Read Syntax for Numerical Data |
| 831 | |
| 832 | The read syntax for integers is a string of digits, optionally |
| 833 | preceded by a minus or plus character, a code indicating the |
| 834 | base in which the integer is encoded, and a code indicating whether |
| 835 | the number is exact or inexact. The supported base codes are: |
| 836 | |
| 837 | @table @code |
| 838 | @item #b |
| 839 | @itemx #B |
| 840 | the integer is written in binary (base 2) |
| 841 | |
| 842 | @item #o |
| 843 | @itemx #O |
| 844 | the integer is written in octal (base 8) |
| 845 | |
| 846 | @item #d |
| 847 | @itemx #D |
| 848 | the integer is written in decimal (base 10) |
| 849 | |
| 850 | @item #x |
| 851 | @itemx #X |
| 852 | the integer is written in hexadecimal (base 16) |
| 853 | @end table |
| 854 | |
| 855 | If the base code is omitted, the integer is assumed to be decimal. The |
| 856 | following examples show how these base codes are used. |
| 857 | |
| 858 | @lisp |
| 859 | -13 |
| 860 | @result{} -13 |
| 861 | |
| 862 | #d-13 |
| 863 | @result{} -13 |
| 864 | |
| 865 | #x-13 |
| 866 | @result{} -19 |
| 867 | |
| 868 | #b+1101 |
| 869 | @result{} 13 |
| 870 | |
| 871 | #o377 |
| 872 | @result{} 255 |
| 873 | @end lisp |
| 874 | |
| 875 | The codes for indicating exactness (which can, incidentally, be applied |
| 876 | to all numerical values) are: |
| 877 | |
| 878 | @table @code |
| 879 | @item #e |
| 880 | @itemx #E |
| 881 | the number is exact |
| 882 | |
| 883 | @item #i |
| 884 | @itemx #I |
| 885 | the number is inexact. |
| 886 | @end table |
| 887 | |
| 888 | If the exactness indicator is omitted, the number is exact unless it |
| 889 | contains a radix point. Since Guile can not represent exact complex |
| 890 | numbers, an error is signalled when asking for them. |
| 891 | |
| 892 | @lisp |
| 893 | (exact? 1.2) |
| 894 | @result{} #f |
| 895 | |
| 896 | (exact? #e1.2) |
| 897 | @result{} #t |
| 898 | |
| 899 | (exact? #e+1i) |
| 900 | ERROR: Wrong type argument |
| 901 | @end lisp |
| 902 | |
| 903 | Guile also understands the syntax @samp{+inf.0} and @samp{-inf.0} for |
| 904 | plus and minus infinity, respectively. The value must be written |
| 905 | exactly as shown, that is, they always must have a sign and exactly |
| 906 | one zero digit after the decimal point. It also understands |
| 907 | @samp{+nan.0} and @samp{-nan.0} for the special `not-a-number' value. |
| 908 | The sign is ignored for `not-a-number' and the value is always printed |
| 909 | as @samp{+nan.0}. |
| 910 | |
| 911 | @node Integer Operations |
| 912 | @subsubsection Operations on Integer Values |
| 913 | @rnindex odd? |
| 914 | @rnindex even? |
| 915 | @rnindex quotient |
| 916 | @rnindex remainder |
| 917 | @rnindex modulo |
| 918 | @rnindex gcd |
| 919 | @rnindex lcm |
| 920 | |
| 921 | @deffn {Scheme Procedure} odd? n |
| 922 | @deffnx {C Function} scm_odd_p (n) |
| 923 | Return @code{#t} if @var{n} is an odd number, @code{#f} |
| 924 | otherwise. |
| 925 | @end deffn |
| 926 | |
| 927 | @deffn {Scheme Procedure} even? n |
| 928 | @deffnx {C Function} scm_even_p (n) |
| 929 | Return @code{#t} if @var{n} is an even number, @code{#f} |
| 930 | otherwise. |
| 931 | @end deffn |
| 932 | |
| 933 | @c begin (texi-doc-string "guile" "quotient") |
| 934 | @c begin (texi-doc-string "guile" "remainder") |
| 935 | @deffn {Scheme Procedure} quotient n d |
| 936 | @deffnx {Scheme Procedure} remainder n d |
| 937 | @deffnx {C Function} scm_quotient (n, d) |
| 938 | @deffnx {C Function} scm_remainder (n, d) |
| 939 | Return the quotient or remainder from @var{n} divided by @var{d}. The |
| 940 | quotient is rounded towards zero, and the remainder will have the same |
| 941 | sign as @var{n}. In all cases quotient and remainder satisfy |
| 942 | @math{@var{n} = @var{q}*@var{d} + @var{r}}. |
| 943 | |
| 944 | @lisp |
| 945 | (remainder 13 4) @result{} 1 |
| 946 | (remainder -13 4) @result{} -1 |
| 947 | @end lisp |
| 948 | |
| 949 | See also @code{truncate-quotient}, @code{truncate-remainder} and |
| 950 | related operations in @ref{Arithmetic}. |
| 951 | @end deffn |
| 952 | |
| 953 | @c begin (texi-doc-string "guile" "modulo") |
| 954 | @deffn {Scheme Procedure} modulo n d |
| 955 | @deffnx {C Function} scm_modulo (n, d) |
| 956 | Return the remainder from @var{n} divided by @var{d}, with the same |
| 957 | sign as @var{d}. |
| 958 | |
| 959 | @lisp |
| 960 | (modulo 13 4) @result{} 1 |
| 961 | (modulo -13 4) @result{} 3 |
| 962 | (modulo 13 -4) @result{} -3 |
| 963 | (modulo -13 -4) @result{} -1 |
| 964 | @end lisp |
| 965 | |
| 966 | See also @code{floor-quotient}, @code{floor-remainder} and |
| 967 | related operations in @ref{Arithmetic}. |
| 968 | @end deffn |
| 969 | |
| 970 | @c begin (texi-doc-string "guile" "gcd") |
| 971 | @deffn {Scheme Procedure} gcd x@dots{} |
| 972 | @deffnx {C Function} scm_gcd (x, y) |
| 973 | Return the greatest common divisor of all arguments. |
| 974 | If called without arguments, 0 is returned. |
| 975 | |
| 976 | The C function @code{scm_gcd} always takes two arguments, while the |
| 977 | Scheme function can take an arbitrary number. |
| 978 | @end deffn |
| 979 | |
| 980 | @c begin (texi-doc-string "guile" "lcm") |
| 981 | @deffn {Scheme Procedure} lcm x@dots{} |
| 982 | @deffnx {C Function} scm_lcm (x, y) |
| 983 | Return the least common multiple of the arguments. |
| 984 | If called without arguments, 1 is returned. |
| 985 | |
| 986 | The C function @code{scm_lcm} always takes two arguments, while the |
| 987 | Scheme function can take an arbitrary number. |
| 988 | @end deffn |
| 989 | |
| 990 | @deffn {Scheme Procedure} modulo-expt n k m |
| 991 | @deffnx {C Function} scm_modulo_expt (n, k, m) |
| 992 | Return @var{n} raised to the integer exponent |
| 993 | @var{k}, modulo @var{m}. |
| 994 | |
| 995 | @lisp |
| 996 | (modulo-expt 2 3 5) |
| 997 | @result{} 3 |
| 998 | @end lisp |
| 999 | @end deffn |
| 1000 | |
| 1001 | @deftypefn {Scheme Procedure} {} exact-integer-sqrt @var{k} |
| 1002 | @deftypefnx {C Function} void scm_exact_integer_sqrt (SCM @var{k}, SCM *@var{s}, SCM *@var{r}) |
| 1003 | Return two exact non-negative integers @var{s} and @var{r} |
| 1004 | such that @math{@var{k} = @var{s}^2 + @var{r}} and |
| 1005 | @math{@var{s}^2 <= @var{k} < (@var{s} + 1)^2}. |
| 1006 | An error is raised if @var{k} is not an exact non-negative integer. |
| 1007 | |
| 1008 | @lisp |
| 1009 | (exact-integer-sqrt 10) @result{} 3 and 1 |
| 1010 | @end lisp |
| 1011 | @end deftypefn |
| 1012 | |
| 1013 | @node Comparison |
| 1014 | @subsubsection Comparison Predicates |
| 1015 | @rnindex zero? |
| 1016 | @rnindex positive? |
| 1017 | @rnindex negative? |
| 1018 | |
| 1019 | The C comparison functions below always takes two arguments, while the |
| 1020 | Scheme functions can take an arbitrary number. Also keep in mind that |
| 1021 | the C functions return one of the Scheme boolean values |
| 1022 | @code{SCM_BOOL_T} or @code{SCM_BOOL_F} which are both true as far as C |
| 1023 | is concerned. Thus, always write @code{scm_is_true (scm_num_eq_p (x, |
| 1024 | y))} when testing the two Scheme numbers @code{x} and @code{y} for |
| 1025 | equality, for example. |
| 1026 | |
| 1027 | @c begin (texi-doc-string "guile" "=") |
| 1028 | @deffn {Scheme Procedure} = |
| 1029 | @deffnx {C Function} scm_num_eq_p (x, y) |
| 1030 | Return @code{#t} if all parameters are numerically equal. |
| 1031 | @end deffn |
| 1032 | |
| 1033 | @c begin (texi-doc-string "guile" "<") |
| 1034 | @deffn {Scheme Procedure} < |
| 1035 | @deffnx {C Function} scm_less_p (x, y) |
| 1036 | Return @code{#t} if the list of parameters is monotonically |
| 1037 | increasing. |
| 1038 | @end deffn |
| 1039 | |
| 1040 | @c begin (texi-doc-string "guile" ">") |
| 1041 | @deffn {Scheme Procedure} > |
| 1042 | @deffnx {C Function} scm_gr_p (x, y) |
| 1043 | Return @code{#t} if the list of parameters is monotonically |
| 1044 | decreasing. |
| 1045 | @end deffn |
| 1046 | |
| 1047 | @c begin (texi-doc-string "guile" "<=") |
| 1048 | @deffn {Scheme Procedure} <= |
| 1049 | @deffnx {C Function} scm_leq_p (x, y) |
| 1050 | Return @code{#t} if the list of parameters is monotonically |
| 1051 | non-decreasing. |
| 1052 | @end deffn |
| 1053 | |
| 1054 | @c begin (texi-doc-string "guile" ">=") |
| 1055 | @deffn {Scheme Procedure} >= |
| 1056 | @deffnx {C Function} scm_geq_p (x, y) |
| 1057 | Return @code{#t} if the list of parameters is monotonically |
| 1058 | non-increasing. |
| 1059 | @end deffn |
| 1060 | |
| 1061 | @c begin (texi-doc-string "guile" "zero?") |
| 1062 | @deffn {Scheme Procedure} zero? z |
| 1063 | @deffnx {C Function} scm_zero_p (z) |
| 1064 | Return @code{#t} if @var{z} is an exact or inexact number equal to |
| 1065 | zero. |
| 1066 | @end deffn |
| 1067 | |
| 1068 | @c begin (texi-doc-string "guile" "positive?") |
| 1069 | @deffn {Scheme Procedure} positive? x |
| 1070 | @deffnx {C Function} scm_positive_p (x) |
| 1071 | Return @code{#t} if @var{x} is an exact or inexact number greater than |
| 1072 | zero. |
| 1073 | @end deffn |
| 1074 | |
| 1075 | @c begin (texi-doc-string "guile" "negative?") |
| 1076 | @deffn {Scheme Procedure} negative? x |
| 1077 | @deffnx {C Function} scm_negative_p (x) |
| 1078 | Return @code{#t} if @var{x} is an exact or inexact number less than |
| 1079 | zero. |
| 1080 | @end deffn |
| 1081 | |
| 1082 | |
| 1083 | @node Conversion |
| 1084 | @subsubsection Converting Numbers To and From Strings |
| 1085 | @rnindex number->string |
| 1086 | @rnindex string->number |
| 1087 | |
| 1088 | The following procedures read and write numbers according to their |
| 1089 | external representation as defined by R5RS (@pxref{Lexical structure, |
| 1090 | R5RS Lexical Structure,, r5rs, The Revised^5 Report on the Algorithmic |
| 1091 | Language Scheme}). @xref{Number Input and Output, the @code{(ice-9 |
| 1092 | i18n)} module}, for locale-dependent number parsing. |
| 1093 | |
| 1094 | @deffn {Scheme Procedure} number->string n [radix] |
| 1095 | @deffnx {C Function} scm_number_to_string (n, radix) |
| 1096 | Return a string holding the external representation of the |
| 1097 | number @var{n} in the given @var{radix}. If @var{n} is |
| 1098 | inexact, a radix of 10 will be used. |
| 1099 | @end deffn |
| 1100 | |
| 1101 | @deffn {Scheme Procedure} string->number string [radix] |
| 1102 | @deffnx {C Function} scm_string_to_number (string, radix) |
| 1103 | Return a number of the maximally precise representation |
| 1104 | expressed by the given @var{string}. @var{radix} must be an |
| 1105 | exact integer, either 2, 8, 10, or 16. If supplied, @var{radix} |
| 1106 | is a default radix that may be overridden by an explicit radix |
| 1107 | prefix in @var{string} (e.g.@: "#o177"). If @var{radix} is not |
| 1108 | supplied, then the default radix is 10. If string is not a |
| 1109 | syntactically valid notation for a number, then |
| 1110 | @code{string->number} returns @code{#f}. |
| 1111 | @end deffn |
| 1112 | |
| 1113 | @deftypefn {C Function} SCM scm_c_locale_stringn_to_number (const char *string, size_t len, unsigned radix) |
| 1114 | As per @code{string->number} above, but taking a C string, as pointer |
| 1115 | and length. The string characters should be in the current locale |
| 1116 | encoding (@code{locale} in the name refers only to that, there's no |
| 1117 | locale-dependent parsing). |
| 1118 | @end deftypefn |
| 1119 | |
| 1120 | |
| 1121 | @node Complex |
| 1122 | @subsubsection Complex Number Operations |
| 1123 | @rnindex make-rectangular |
| 1124 | @rnindex make-polar |
| 1125 | @rnindex real-part |
| 1126 | @rnindex imag-part |
| 1127 | @rnindex magnitude |
| 1128 | @rnindex angle |
| 1129 | |
| 1130 | @deffn {Scheme Procedure} make-rectangular real_part imaginary_part |
| 1131 | @deffnx {C Function} scm_make_rectangular (real_part, imaginary_part) |
| 1132 | Return a complex number constructed of the given @var{real-part} and @var{imaginary-part} parts. |
| 1133 | @end deffn |
| 1134 | |
| 1135 | @deffn {Scheme Procedure} make-polar mag ang |
| 1136 | @deffnx {C Function} scm_make_polar (mag, ang) |
| 1137 | @cindex polar form |
| 1138 | Return the complex number @var{mag} * e^(i * @var{ang}). |
| 1139 | @end deffn |
| 1140 | |
| 1141 | @c begin (texi-doc-string "guile" "real-part") |
| 1142 | @deffn {Scheme Procedure} real-part z |
| 1143 | @deffnx {C Function} scm_real_part (z) |
| 1144 | Return the real part of the number @var{z}. |
| 1145 | @end deffn |
| 1146 | |
| 1147 | @c begin (texi-doc-string "guile" "imag-part") |
| 1148 | @deffn {Scheme Procedure} imag-part z |
| 1149 | @deffnx {C Function} scm_imag_part (z) |
| 1150 | Return the imaginary part of the number @var{z}. |
| 1151 | @end deffn |
| 1152 | |
| 1153 | @c begin (texi-doc-string "guile" "magnitude") |
| 1154 | @deffn {Scheme Procedure} magnitude z |
| 1155 | @deffnx {C Function} scm_magnitude (z) |
| 1156 | Return the magnitude of the number @var{z}. This is the same as |
| 1157 | @code{abs} for real arguments, but also allows complex numbers. |
| 1158 | @end deffn |
| 1159 | |
| 1160 | @c begin (texi-doc-string "guile" "angle") |
| 1161 | @deffn {Scheme Procedure} angle z |
| 1162 | @deffnx {C Function} scm_angle (z) |
| 1163 | Return the angle of the complex number @var{z}. |
| 1164 | @end deffn |
| 1165 | |
| 1166 | @deftypefn {C Function} SCM scm_c_make_rectangular (double re, double im) |
| 1167 | @deftypefnx {C Function} SCM scm_c_make_polar (double x, double y) |
| 1168 | Like @code{scm_make_rectangular} or @code{scm_make_polar}, |
| 1169 | respectively, but these functions take @code{double}s as their |
| 1170 | arguments. |
| 1171 | @end deftypefn |
| 1172 | |
| 1173 | @deftypefn {C Function} double scm_c_real_part (z) |
| 1174 | @deftypefnx {C Function} double scm_c_imag_part (z) |
| 1175 | Returns the real or imaginary part of @var{z} as a @code{double}. |
| 1176 | @end deftypefn |
| 1177 | |
| 1178 | @deftypefn {C Function} double scm_c_magnitude (z) |
| 1179 | @deftypefnx {C Function} double scm_c_angle (z) |
| 1180 | Returns the magnitude or angle of @var{z} as a @code{double}. |
| 1181 | @end deftypefn |
| 1182 | |
| 1183 | |
| 1184 | @node Arithmetic |
| 1185 | @subsubsection Arithmetic Functions |
| 1186 | @rnindex max |
| 1187 | @rnindex min |
| 1188 | @rnindex + |
| 1189 | @rnindex * |
| 1190 | @rnindex - |
| 1191 | @rnindex / |
| 1192 | @findex 1+ |
| 1193 | @findex 1- |
| 1194 | @rnindex abs |
| 1195 | @rnindex floor |
| 1196 | @rnindex ceiling |
| 1197 | @rnindex truncate |
| 1198 | @rnindex round |
| 1199 | @rnindex euclidean/ |
| 1200 | @rnindex euclidean-quotient |
| 1201 | @rnindex euclidean-remainder |
| 1202 | @rnindex floor/ |
| 1203 | @rnindex floor-quotient |
| 1204 | @rnindex floor-remainder |
| 1205 | @rnindex ceiling/ |
| 1206 | @rnindex ceiling-quotient |
| 1207 | @rnindex ceiling-remainder |
| 1208 | @rnindex truncate/ |
| 1209 | @rnindex truncate-quotient |
| 1210 | @rnindex truncate-remainder |
| 1211 | @rnindex centered/ |
| 1212 | @rnindex centered-quotient |
| 1213 | @rnindex centered-remainder |
| 1214 | @rnindex round/ |
| 1215 | @rnindex round-quotient |
| 1216 | @rnindex round-remainder |
| 1217 | |
| 1218 | The C arithmetic functions below always takes two arguments, while the |
| 1219 | Scheme functions can take an arbitrary number. When you need to |
| 1220 | invoke them with just one argument, for example to compute the |
| 1221 | equivalent of @code{(- x)}, pass @code{SCM_UNDEFINED} as the second |
| 1222 | one: @code{scm_difference (x, SCM_UNDEFINED)}. |
| 1223 | |
| 1224 | @c begin (texi-doc-string "guile" "+") |
| 1225 | @deffn {Scheme Procedure} + z1 @dots{} |
| 1226 | @deffnx {C Function} scm_sum (z1, z2) |
| 1227 | Return the sum of all parameter values. Return 0 if called without any |
| 1228 | parameters. |
| 1229 | @end deffn |
| 1230 | |
| 1231 | @c begin (texi-doc-string "guile" "-") |
| 1232 | @deffn {Scheme Procedure} - z1 z2 @dots{} |
| 1233 | @deffnx {C Function} scm_difference (z1, z2) |
| 1234 | If called with one argument @var{z1}, -@var{z1} is returned. Otherwise |
| 1235 | the sum of all but the first argument are subtracted from the first |
| 1236 | argument. |
| 1237 | @end deffn |
| 1238 | |
| 1239 | @c begin (texi-doc-string "guile" "*") |
| 1240 | @deffn {Scheme Procedure} * z1 @dots{} |
| 1241 | @deffnx {C Function} scm_product (z1, z2) |
| 1242 | Return the product of all arguments. If called without arguments, 1 is |
| 1243 | returned. |
| 1244 | @end deffn |
| 1245 | |
| 1246 | @c begin (texi-doc-string "guile" "/") |
| 1247 | @deffn {Scheme Procedure} / z1 z2 @dots{} |
| 1248 | @deffnx {C Function} scm_divide (z1, z2) |
| 1249 | Divide the first argument by the product of the remaining arguments. If |
| 1250 | called with one argument @var{z1}, 1/@var{z1} is returned. |
| 1251 | @end deffn |
| 1252 | |
| 1253 | @deffn {Scheme Procedure} 1+ z |
| 1254 | @deffnx {C Function} scm_oneplus (z) |
| 1255 | Return @math{@var{z} + 1}. |
| 1256 | @end deffn |
| 1257 | |
| 1258 | @deffn {Scheme Procedure} 1- z |
| 1259 | @deffnx {C function} scm_oneminus (z) |
| 1260 | Return @math{@var{z} - 1}. |
| 1261 | @end deffn |
| 1262 | |
| 1263 | @c begin (texi-doc-string "guile" "abs") |
| 1264 | @deffn {Scheme Procedure} abs x |
| 1265 | @deffnx {C Function} scm_abs (x) |
| 1266 | Return the absolute value of @var{x}. |
| 1267 | |
| 1268 | @var{x} must be a number with zero imaginary part. To calculate the |
| 1269 | magnitude of a complex number, use @code{magnitude} instead. |
| 1270 | @end deffn |
| 1271 | |
| 1272 | @c begin (texi-doc-string "guile" "max") |
| 1273 | @deffn {Scheme Procedure} max x1 x2 @dots{} |
| 1274 | @deffnx {C Function} scm_max (x1, x2) |
| 1275 | Return the maximum of all parameter values. |
| 1276 | @end deffn |
| 1277 | |
| 1278 | @c begin (texi-doc-string "guile" "min") |
| 1279 | @deffn {Scheme Procedure} min x1 x2 @dots{} |
| 1280 | @deffnx {C Function} scm_min (x1, x2) |
| 1281 | Return the minimum of all parameter values. |
| 1282 | @end deffn |
| 1283 | |
| 1284 | @c begin (texi-doc-string "guile" "truncate") |
| 1285 | @deffn {Scheme Procedure} truncate x |
| 1286 | @deffnx {C Function} scm_truncate_number (x) |
| 1287 | Round the inexact number @var{x} towards zero. |
| 1288 | @end deffn |
| 1289 | |
| 1290 | @c begin (texi-doc-string "guile" "round") |
| 1291 | @deffn {Scheme Procedure} round x |
| 1292 | @deffnx {C Function} scm_round_number (x) |
| 1293 | Round the inexact number @var{x} to the nearest integer. When exactly |
| 1294 | halfway between two integers, round to the even one. |
| 1295 | @end deffn |
| 1296 | |
| 1297 | @c begin (texi-doc-string "guile" "floor") |
| 1298 | @deffn {Scheme Procedure} floor x |
| 1299 | @deffnx {C Function} scm_floor (x) |
| 1300 | Round the number @var{x} towards minus infinity. |
| 1301 | @end deffn |
| 1302 | |
| 1303 | @c begin (texi-doc-string "guile" "ceiling") |
| 1304 | @deffn {Scheme Procedure} ceiling x |
| 1305 | @deffnx {C Function} scm_ceiling (x) |
| 1306 | Round the number @var{x} towards infinity. |
| 1307 | @end deffn |
| 1308 | |
| 1309 | @deftypefn {C Function} double scm_c_truncate (double x) |
| 1310 | @deftypefnx {C Function} double scm_c_round (double x) |
| 1311 | Like @code{scm_truncate_number} or @code{scm_round_number}, |
| 1312 | respectively, but these functions take and return @code{double} |
| 1313 | values. |
| 1314 | @end deftypefn |
| 1315 | |
| 1316 | @deftypefn {Scheme Procedure} {} euclidean/ @var{x} @var{y} |
| 1317 | @deftypefnx {Scheme Procedure} {} euclidean-quotient @var{x} @var{y} |
| 1318 | @deftypefnx {Scheme Procedure} {} euclidean-remainder @var{x} @var{y} |
| 1319 | @deftypefnx {C Function} void scm_euclidean_divide (SCM @var{x}, SCM @var{y}, SCM *@var{q}, SCM *@var{r}) |
| 1320 | @deftypefnx {C Function} SCM scm_euclidean_quotient (SCM @var{x}, SCM @var{y}) |
| 1321 | @deftypefnx {C Function} SCM scm_euclidean_remainder (SCM @var{x}, SCM @var{y}) |
| 1322 | These procedures accept two real numbers @var{x} and @var{y}, where the |
| 1323 | divisor @var{y} must be non-zero. @code{euclidean-quotient} returns the |
| 1324 | integer @var{q} and @code{euclidean-remainder} returns the real number |
| 1325 | @var{r} such that @math{@var{x} = @var{q}*@var{y} + @var{r}} and |
| 1326 | @math{0 <= @var{r} < |@var{y}|}. @code{euclidean/} returns both @var{q} and |
| 1327 | @var{r}, and is more efficient than computing each separately. Note |
| 1328 | that when @math{@var{y} > 0}, @code{euclidean-quotient} returns |
| 1329 | @math{floor(@var{x}/@var{y})}, otherwise it returns |
| 1330 | @math{ceiling(@var{x}/@var{y})}. |
| 1331 | |
| 1332 | Note that these operators are equivalent to the R6RS operators |
| 1333 | @code{div}, @code{mod}, and @code{div-and-mod}. |
| 1334 | |
| 1335 | @lisp |
| 1336 | (euclidean-quotient 123 10) @result{} 12 |
| 1337 | (euclidean-remainder 123 10) @result{} 3 |
| 1338 | (euclidean/ 123 10) @result{} 12 and 3 |
| 1339 | (euclidean/ 123 -10) @result{} -12 and 3 |
| 1340 | (euclidean/ -123 10) @result{} -13 and 7 |
| 1341 | (euclidean/ -123 -10) @result{} 13 and 7 |
| 1342 | (euclidean/ -123.2 -63.5) @result{} 2.0 and 3.8 |
| 1343 | (euclidean/ 16/3 -10/7) @result{} -3 and 22/21 |
| 1344 | @end lisp |
| 1345 | @end deftypefn |
| 1346 | |
| 1347 | @deftypefn {Scheme Procedure} {} floor/ @var{x} @var{y} |
| 1348 | @deftypefnx {Scheme Procedure} {} floor-quotient @var{x} @var{y} |
| 1349 | @deftypefnx {Scheme Procedure} {} floor-remainder @var{x} @var{y} |
| 1350 | @deftypefnx {C Function} void scm_floor_divide (SCM @var{x}, SCM @var{y}, SCM *@var{q}, SCM *@var{r}) |
| 1351 | @deftypefnx {C Function} SCM scm_floor_quotient (@var{x}, @var{y}) |
| 1352 | @deftypefnx {C Function} SCM scm_floor_remainder (@var{x}, @var{y}) |
| 1353 | These procedures accept two real numbers @var{x} and @var{y}, where the |
| 1354 | divisor @var{y} must be non-zero. @code{floor-quotient} returns the |
| 1355 | integer @var{q} and @code{floor-remainder} returns the real number |
| 1356 | @var{r} such that @math{@var{q} = floor(@var{x}/@var{y})} and |
| 1357 | @math{@var{x} = @var{q}*@var{y} + @var{r}}. @code{floor/} returns |
| 1358 | both @var{q} and @var{r}, and is more efficient than computing each |
| 1359 | separately. Note that @var{r}, if non-zero, will have the same sign |
| 1360 | as @var{y}. |
| 1361 | |
| 1362 | When @var{x} and @var{y} are integers, @code{floor-remainder} is |
| 1363 | equivalent to the R5RS integer-only operator @code{modulo}. |
| 1364 | |
| 1365 | @lisp |
| 1366 | (floor-quotient 123 10) @result{} 12 |
| 1367 | (floor-remainder 123 10) @result{} 3 |
| 1368 | (floor/ 123 10) @result{} 12 and 3 |
| 1369 | (floor/ 123 -10) @result{} -13 and -7 |
| 1370 | (floor/ -123 10) @result{} -13 and 7 |
| 1371 | (floor/ -123 -10) @result{} 12 and -3 |
| 1372 | (floor/ -123.2 -63.5) @result{} 1.0 and -59.7 |
| 1373 | (floor/ 16/3 -10/7) @result{} -4 and -8/21 |
| 1374 | @end lisp |
| 1375 | @end deftypefn |
| 1376 | |
| 1377 | @deftypefn {Scheme Procedure} {} ceiling/ @var{x} @var{y} |
| 1378 | @deftypefnx {Scheme Procedure} {} ceiling-quotient @var{x} @var{y} |
| 1379 | @deftypefnx {Scheme Procedure} {} ceiling-remainder @var{x} @var{y} |
| 1380 | @deftypefnx {C Function} void scm_ceiling_divide (SCM @var{x}, SCM @var{y}, SCM *@var{q}, SCM *@var{r}) |
| 1381 | @deftypefnx {C Function} SCM scm_ceiling_quotient (@var{x}, @var{y}) |
| 1382 | @deftypefnx {C Function} SCM scm_ceiling_remainder (@var{x}, @var{y}) |
| 1383 | These procedures accept two real numbers @var{x} and @var{y}, where the |
| 1384 | divisor @var{y} must be non-zero. @code{ceiling-quotient} returns the |
| 1385 | integer @var{q} and @code{ceiling-remainder} returns the real number |
| 1386 | @var{r} such that @math{@var{q} = ceiling(@var{x}/@var{y})} and |
| 1387 | @math{@var{x} = @var{q}*@var{y} + @var{r}}. @code{ceiling/} returns |
| 1388 | both @var{q} and @var{r}, and is more efficient than computing each |
| 1389 | separately. Note that @var{r}, if non-zero, will have the opposite sign |
| 1390 | of @var{y}. |
| 1391 | |
| 1392 | @lisp |
| 1393 | (ceiling-quotient 123 10) @result{} 13 |
| 1394 | (ceiling-remainder 123 10) @result{} -7 |
| 1395 | (ceiling/ 123 10) @result{} 13 and -7 |
| 1396 | (ceiling/ 123 -10) @result{} -12 and 3 |
| 1397 | (ceiling/ -123 10) @result{} -12 and -3 |
| 1398 | (ceiling/ -123 -10) @result{} 13 and 7 |
| 1399 | (ceiling/ -123.2 -63.5) @result{} 2.0 and 3.8 |
| 1400 | (ceiling/ 16/3 -10/7) @result{} -3 and 22/21 |
| 1401 | @end lisp |
| 1402 | @end deftypefn |
| 1403 | |
| 1404 | @deftypefn {Scheme Procedure} {} truncate/ @var{x} @var{y} |
| 1405 | @deftypefnx {Scheme Procedure} {} truncate-quotient @var{x} @var{y} |
| 1406 | @deftypefnx {Scheme Procedure} {} truncate-remainder @var{x} @var{y} |
| 1407 | @deftypefnx {C Function} void scm_truncate_divide (SCM @var{x}, SCM @var{y}, SCM *@var{q}, SCM *@var{r}) |
| 1408 | @deftypefnx {C Function} SCM scm_truncate_quotient (@var{x}, @var{y}) |
| 1409 | @deftypefnx {C Function} SCM scm_truncate_remainder (@var{x}, @var{y}) |
| 1410 | These procedures accept two real numbers @var{x} and @var{y}, where the |
| 1411 | divisor @var{y} must be non-zero. @code{truncate-quotient} returns the |
| 1412 | integer @var{q} and @code{truncate-remainder} returns the real number |
| 1413 | @var{r} such that @var{q} is @math{@var{x}/@var{y}} rounded toward zero, |
| 1414 | and @math{@var{x} = @var{q}*@var{y} + @var{r}}. @code{truncate/} returns |
| 1415 | both @var{q} and @var{r}, and is more efficient than computing each |
| 1416 | separately. Note that @var{r}, if non-zero, will have the same sign |
| 1417 | as @var{x}. |
| 1418 | |
| 1419 | When @var{x} and @var{y} are integers, these operators are |
| 1420 | equivalent to the R5RS integer-only operators @code{quotient} and |
| 1421 | @code{remainder}. |
| 1422 | |
| 1423 | @lisp |
| 1424 | (truncate-quotient 123 10) @result{} 12 |
| 1425 | (truncate-remainder 123 10) @result{} 3 |
| 1426 | (truncate/ 123 10) @result{} 12 and 3 |
| 1427 | (truncate/ 123 -10) @result{} -12 and 3 |
| 1428 | (truncate/ -123 10) @result{} -12 and -3 |
| 1429 | (truncate/ -123 -10) @result{} 12 and -3 |
| 1430 | (truncate/ -123.2 -63.5) @result{} 1.0 and -59.7 |
| 1431 | (truncate/ 16/3 -10/7) @result{} -3 and 22/21 |
| 1432 | @end lisp |
| 1433 | @end deftypefn |
| 1434 | |
| 1435 | @deftypefn {Scheme Procedure} {} centered/ @var{x} @var{y} |
| 1436 | @deftypefnx {Scheme Procedure} {} centered-quotient @var{x} @var{y} |
| 1437 | @deftypefnx {Scheme Procedure} {} centered-remainder @var{x} @var{y} |
| 1438 | @deftypefnx {C Function} void scm_centered_divide (SCM @var{x}, SCM @var{y}, SCM *@var{q}, SCM *@var{r}) |
| 1439 | @deftypefnx {C Function} SCM scm_centered_quotient (SCM @var{x}, SCM @var{y}) |
| 1440 | @deftypefnx {C Function} SCM scm_centered_remainder (SCM @var{x}, SCM @var{y}) |
| 1441 | These procedures accept two real numbers @var{x} and @var{y}, where the |
| 1442 | divisor @var{y} must be non-zero. @code{centered-quotient} returns the |
| 1443 | integer @var{q} and @code{centered-remainder} returns the real number |
| 1444 | @var{r} such that @math{@var{x} = @var{q}*@var{y} + @var{r}} and |
| 1445 | @math{-|@var{y}/2| <= @var{r} < |@var{y}/2|}. @code{centered/} |
| 1446 | returns both @var{q} and @var{r}, and is more efficient than computing |
| 1447 | each separately. |
| 1448 | |
| 1449 | Note that @code{centered-quotient} returns @math{@var{x}/@var{y}} |
| 1450 | rounded to the nearest integer. When @math{@var{x}/@var{y}} lies |
| 1451 | exactly half-way between two integers, the tie is broken according to |
| 1452 | the sign of @var{y}. If @math{@var{y} > 0}, ties are rounded toward |
| 1453 | positive infinity, otherwise they are rounded toward negative infinity. |
| 1454 | This is a consequence of the requirement that |
| 1455 | @math{-|@var{y}/2| <= @var{r} < |@var{y}/2|}. |
| 1456 | |
| 1457 | Note that these operators are equivalent to the R6RS operators |
| 1458 | @code{div0}, @code{mod0}, and @code{div0-and-mod0}. |
| 1459 | |
| 1460 | @lisp |
| 1461 | (centered-quotient 123 10) @result{} 12 |
| 1462 | (centered-remainder 123 10) @result{} 3 |
| 1463 | (centered/ 123 10) @result{} 12 and 3 |
| 1464 | (centered/ 123 -10) @result{} -12 and 3 |
| 1465 | (centered/ -123 10) @result{} -12 and -3 |
| 1466 | (centered/ -123 -10) @result{} 12 and -3 |
| 1467 | (centered/ 125 10) @result{} 13 and -5 |
| 1468 | (centered/ 127 10) @result{} 13 and -3 |
| 1469 | (centered/ 135 10) @result{} 14 and -5 |
| 1470 | (centered/ -123.2 -63.5) @result{} 2.0 and 3.8 |
| 1471 | (centered/ 16/3 -10/7) @result{} -4 and -8/21 |
| 1472 | @end lisp |
| 1473 | @end deftypefn |
| 1474 | |
| 1475 | @deftypefn {Scheme Procedure} {} round/ @var{x} @var{y} |
| 1476 | @deftypefnx {Scheme Procedure} {} round-quotient @var{x} @var{y} |
| 1477 | @deftypefnx {Scheme Procedure} {} round-remainder @var{x} @var{y} |
| 1478 | @deftypefnx {C Function} void scm_round_divide (SCM @var{x}, SCM @var{y}, SCM *@var{q}, SCM *@var{r}) |
| 1479 | @deftypefnx {C Function} SCM scm_round_quotient (@var{x}, @var{y}) |
| 1480 | @deftypefnx {C Function} SCM scm_round_remainder (@var{x}, @var{y}) |
| 1481 | These procedures accept two real numbers @var{x} and @var{y}, where the |
| 1482 | divisor @var{y} must be non-zero. @code{round-quotient} returns the |
| 1483 | integer @var{q} and @code{round-remainder} returns the real number |
| 1484 | @var{r} such that @math{@var{x} = @var{q}*@var{y} + @var{r}} and |
| 1485 | @var{q} is @math{@var{x}/@var{y}} rounded to the nearest integer, |
| 1486 | with ties going to the nearest even integer. @code{round/} |
| 1487 | returns both @var{q} and @var{r}, and is more efficient than computing |
| 1488 | each separately. |
| 1489 | |
| 1490 | Note that @code{round/} and @code{centered/} are almost equivalent, but |
| 1491 | their behavior differs when @math{@var{x}/@var{y}} lies exactly half-way |
| 1492 | between two integers. In this case, @code{round/} chooses the nearest |
| 1493 | even integer, whereas @code{centered/} chooses in such a way to satisfy |
| 1494 | the constraint @math{-|@var{y}/2| <= @var{r} < |@var{y}/2|}, which |
| 1495 | is stronger than the corresponding constraint for @code{round/}, |
| 1496 | @math{-|@var{y}/2| <= @var{r} <= |@var{y}/2|}. In particular, |
| 1497 | when @var{x} and @var{y} are integers, the number of possible remainders |
| 1498 | returned by @code{centered/} is @math{|@var{y}|}, whereas the number of |
| 1499 | possible remainders returned by @code{round/} is @math{|@var{y}|+1} when |
| 1500 | @var{y} is even. |
| 1501 | |
| 1502 | @lisp |
| 1503 | (round-quotient 123 10) @result{} 12 |
| 1504 | (round-remainder 123 10) @result{} 3 |
| 1505 | (round/ 123 10) @result{} 12 and 3 |
| 1506 | (round/ 123 -10) @result{} -12 and 3 |
| 1507 | (round/ -123 10) @result{} -12 and -3 |
| 1508 | (round/ -123 -10) @result{} 12 and -3 |
| 1509 | (round/ 125 10) @result{} 12 and 5 |
| 1510 | (round/ 127 10) @result{} 13 and -3 |
| 1511 | (round/ 135 10) @result{} 14 and -5 |
| 1512 | (round/ -123.2 -63.5) @result{} 2.0 and 3.8 |
| 1513 | (round/ 16/3 -10/7) @result{} -4 and -8/21 |
| 1514 | @end lisp |
| 1515 | @end deftypefn |
| 1516 | |
| 1517 | @node Scientific |
| 1518 | @subsubsection Scientific Functions |
| 1519 | |
| 1520 | The following procedures accept any kind of number as arguments, |
| 1521 | including complex numbers. |
| 1522 | |
| 1523 | @rnindex sqrt |
| 1524 | @c begin (texi-doc-string "guile" "sqrt") |
| 1525 | @deffn {Scheme Procedure} sqrt z |
| 1526 | Return the square root of @var{z}. Of the two possible roots |
| 1527 | (positive and negative), the one with a positive real part is |
| 1528 | returned, or if that's zero then a positive imaginary part. Thus, |
| 1529 | |
| 1530 | @example |
| 1531 | (sqrt 9.0) @result{} 3.0 |
| 1532 | (sqrt -9.0) @result{} 0.0+3.0i |
| 1533 | (sqrt 1.0+1.0i) @result{} 1.09868411346781+0.455089860562227i |
| 1534 | (sqrt -1.0-1.0i) @result{} 0.455089860562227-1.09868411346781i |
| 1535 | @end example |
| 1536 | @end deffn |
| 1537 | |
| 1538 | @rnindex expt |
| 1539 | @c begin (texi-doc-string "guile" "expt") |
| 1540 | @deffn {Scheme Procedure} expt z1 z2 |
| 1541 | Return @var{z1} raised to the power of @var{z2}. |
| 1542 | @end deffn |
| 1543 | |
| 1544 | @rnindex sin |
| 1545 | @c begin (texi-doc-string "guile" "sin") |
| 1546 | @deffn {Scheme Procedure} sin z |
| 1547 | Return the sine of @var{z}. |
| 1548 | @end deffn |
| 1549 | |
| 1550 | @rnindex cos |
| 1551 | @c begin (texi-doc-string "guile" "cos") |
| 1552 | @deffn {Scheme Procedure} cos z |
| 1553 | Return the cosine of @var{z}. |
| 1554 | @end deffn |
| 1555 | |
| 1556 | @rnindex tan |
| 1557 | @c begin (texi-doc-string "guile" "tan") |
| 1558 | @deffn {Scheme Procedure} tan z |
| 1559 | Return the tangent of @var{z}. |
| 1560 | @end deffn |
| 1561 | |
| 1562 | @rnindex asin |
| 1563 | @c begin (texi-doc-string "guile" "asin") |
| 1564 | @deffn {Scheme Procedure} asin z |
| 1565 | Return the arcsine of @var{z}. |
| 1566 | @end deffn |
| 1567 | |
| 1568 | @rnindex acos |
| 1569 | @c begin (texi-doc-string "guile" "acos") |
| 1570 | @deffn {Scheme Procedure} acos z |
| 1571 | Return the arccosine of @var{z}. |
| 1572 | @end deffn |
| 1573 | |
| 1574 | @rnindex atan |
| 1575 | @c begin (texi-doc-string "guile" "atan") |
| 1576 | @deffn {Scheme Procedure} atan z |
| 1577 | @deffnx {Scheme Procedure} atan y x |
| 1578 | Return the arctangent of @var{z}, or of @math{@var{y}/@var{x}}. |
| 1579 | @end deffn |
| 1580 | |
| 1581 | @rnindex exp |
| 1582 | @c begin (texi-doc-string "guile" "exp") |
| 1583 | @deffn {Scheme Procedure} exp z |
| 1584 | Return e to the power of @var{z}, where e is the base of natural |
| 1585 | logarithms (2.71828@dots{}). |
| 1586 | @end deffn |
| 1587 | |
| 1588 | @rnindex log |
| 1589 | @c begin (texi-doc-string "guile" "log") |
| 1590 | @deffn {Scheme Procedure} log z |
| 1591 | Return the natural logarithm of @var{z}. |
| 1592 | @end deffn |
| 1593 | |
| 1594 | @c begin (texi-doc-string "guile" "log10") |
| 1595 | @deffn {Scheme Procedure} log10 z |
| 1596 | Return the base 10 logarithm of @var{z}. |
| 1597 | @end deffn |
| 1598 | |
| 1599 | @c begin (texi-doc-string "guile" "sinh") |
| 1600 | @deffn {Scheme Procedure} sinh z |
| 1601 | Return the hyperbolic sine of @var{z}. |
| 1602 | @end deffn |
| 1603 | |
| 1604 | @c begin (texi-doc-string "guile" "cosh") |
| 1605 | @deffn {Scheme Procedure} cosh z |
| 1606 | Return the hyperbolic cosine of @var{z}. |
| 1607 | @end deffn |
| 1608 | |
| 1609 | @c begin (texi-doc-string "guile" "tanh") |
| 1610 | @deffn {Scheme Procedure} tanh z |
| 1611 | Return the hyperbolic tangent of @var{z}. |
| 1612 | @end deffn |
| 1613 | |
| 1614 | @c begin (texi-doc-string "guile" "asinh") |
| 1615 | @deffn {Scheme Procedure} asinh z |
| 1616 | Return the hyperbolic arcsine of @var{z}. |
| 1617 | @end deffn |
| 1618 | |
| 1619 | @c begin (texi-doc-string "guile" "acosh") |
| 1620 | @deffn {Scheme Procedure} acosh z |
| 1621 | Return the hyperbolic arccosine of @var{z}. |
| 1622 | @end deffn |
| 1623 | |
| 1624 | @c begin (texi-doc-string "guile" "atanh") |
| 1625 | @deffn {Scheme Procedure} atanh z |
| 1626 | Return the hyperbolic arctangent of @var{z}. |
| 1627 | @end deffn |
| 1628 | |
| 1629 | |
| 1630 | @node Bitwise Operations |
| 1631 | @subsubsection Bitwise Operations |
| 1632 | |
| 1633 | For the following bitwise functions, negative numbers are treated as |
| 1634 | infinite precision twos-complements. For instance @math{-6} is bits |
| 1635 | @math{@dots{}111010}, with infinitely many ones on the left. It can |
| 1636 | be seen that adding 6 (binary 110) to such a bit pattern gives all |
| 1637 | zeros. |
| 1638 | |
| 1639 | @deffn {Scheme Procedure} logand n1 n2 @dots{} |
| 1640 | @deffnx {C Function} scm_logand (n1, n2) |
| 1641 | Return the bitwise @sc{and} of the integer arguments. |
| 1642 | |
| 1643 | @lisp |
| 1644 | (logand) @result{} -1 |
| 1645 | (logand 7) @result{} 7 |
| 1646 | (logand #b111 #b011 #b001) @result{} 1 |
| 1647 | @end lisp |
| 1648 | @end deffn |
| 1649 | |
| 1650 | @deffn {Scheme Procedure} logior n1 n2 @dots{} |
| 1651 | @deffnx {C Function} scm_logior (n1, n2) |
| 1652 | Return the bitwise @sc{or} of the integer arguments. |
| 1653 | |
| 1654 | @lisp |
| 1655 | (logior) @result{} 0 |
| 1656 | (logior 7) @result{} 7 |
| 1657 | (logior #b000 #b001 #b011) @result{} 3 |
| 1658 | @end lisp |
| 1659 | @end deffn |
| 1660 | |
| 1661 | @deffn {Scheme Procedure} logxor n1 n2 @dots{} |
| 1662 | @deffnx {C Function} scm_loxor (n1, n2) |
| 1663 | Return the bitwise @sc{xor} of the integer arguments. A bit is |
| 1664 | set in the result if it is set in an odd number of arguments. |
| 1665 | |
| 1666 | @lisp |
| 1667 | (logxor) @result{} 0 |
| 1668 | (logxor 7) @result{} 7 |
| 1669 | (logxor #b000 #b001 #b011) @result{} 2 |
| 1670 | (logxor #b000 #b001 #b011 #b011) @result{} 1 |
| 1671 | @end lisp |
| 1672 | @end deffn |
| 1673 | |
| 1674 | @deffn {Scheme Procedure} lognot n |
| 1675 | @deffnx {C Function} scm_lognot (n) |
| 1676 | Return the integer which is the ones-complement of the integer |
| 1677 | argument, ie.@: each 0 bit is changed to 1 and each 1 bit to 0. |
| 1678 | |
| 1679 | @lisp |
| 1680 | (number->string (lognot #b10000000) 2) |
| 1681 | @result{} "-10000001" |
| 1682 | (number->string (lognot #b0) 2) |
| 1683 | @result{} "-1" |
| 1684 | @end lisp |
| 1685 | @end deffn |
| 1686 | |
| 1687 | @deffn {Scheme Procedure} logtest j k |
| 1688 | @deffnx {C Function} scm_logtest (j, k) |
| 1689 | Test whether @var{j} and @var{k} have any 1 bits in common. This is |
| 1690 | equivalent to @code{(not (zero? (logand j k)))}, but without actually |
| 1691 | calculating the @code{logand}, just testing for non-zero. |
| 1692 | |
| 1693 | @lisp |
| 1694 | (logtest #b0100 #b1011) @result{} #f |
| 1695 | (logtest #b0100 #b0111) @result{} #t |
| 1696 | @end lisp |
| 1697 | @end deffn |
| 1698 | |
| 1699 | @deffn {Scheme Procedure} logbit? index j |
| 1700 | @deffnx {C Function} scm_logbit_p (index, j) |
| 1701 | Test whether bit number @var{index} in @var{j} is set. @var{index} |
| 1702 | starts from 0 for the least significant bit. |
| 1703 | |
| 1704 | @lisp |
| 1705 | (logbit? 0 #b1101) @result{} #t |
| 1706 | (logbit? 1 #b1101) @result{} #f |
| 1707 | (logbit? 2 #b1101) @result{} #t |
| 1708 | (logbit? 3 #b1101) @result{} #t |
| 1709 | (logbit? 4 #b1101) @result{} #f |
| 1710 | @end lisp |
| 1711 | @end deffn |
| 1712 | |
| 1713 | @deffn {Scheme Procedure} ash n count |
| 1714 | @deffnx {C Function} scm_ash (n, count) |
| 1715 | Return @math{floor(n * 2^count)}. |
| 1716 | @var{n} and @var{count} must be exact integers. |
| 1717 | |
| 1718 | With @var{n} viewed as an infinite-precision twos-complement |
| 1719 | integer, @code{ash} means a left shift introducing zero bits |
| 1720 | when @var{count} is positive, or a right shift dropping bits |
| 1721 | when @var{count} is negative. This is an ``arithmetic'' shift. |
| 1722 | |
| 1723 | @lisp |
| 1724 | (number->string (ash #b1 3) 2) @result{} "1000" |
| 1725 | (number->string (ash #b1010 -1) 2) @result{} "101" |
| 1726 | |
| 1727 | ;; -23 is bits ...11101001, -6 is bits ...111010 |
| 1728 | (ash -23 -2) @result{} -6 |
| 1729 | @end lisp |
| 1730 | @end deffn |
| 1731 | |
| 1732 | @deffn {Scheme Procedure} round-ash n count |
| 1733 | @deffnx {C Function} scm_round_ash (n, count) |
| 1734 | Return @math{round(n * 2^count)}. |
| 1735 | @var{n} and @var{count} must be exact integers. |
| 1736 | |
| 1737 | With @var{n} viewed as an infinite-precision twos-complement |
| 1738 | integer, @code{round-ash} means a left shift introducing zero |
| 1739 | bits when @var{count} is positive, or a right shift rounding |
| 1740 | to the nearest integer (with ties going to the nearest even |
| 1741 | integer) when @var{count} is negative. This is a rounded |
| 1742 | ``arithmetic'' shift. |
| 1743 | |
| 1744 | @lisp |
| 1745 | (number->string (round-ash #b1 3) 2) @result{} \"1000\" |
| 1746 | (number->string (round-ash #b1010 -1) 2) @result{} \"101\" |
| 1747 | (number->string (round-ash #b1010 -2) 2) @result{} \"10\" |
| 1748 | (number->string (round-ash #b1011 -2) 2) @result{} \"11\" |
| 1749 | (number->string (round-ash #b1101 -2) 2) @result{} \"11\" |
| 1750 | (number->string (round-ash #b1110 -2) 2) @result{} \"100\" |
| 1751 | @end lisp |
| 1752 | @end deffn |
| 1753 | |
| 1754 | @deffn {Scheme Procedure} logcount n |
| 1755 | @deffnx {C Function} scm_logcount (n) |
| 1756 | Return the number of bits in integer @var{n}. If @var{n} is |
| 1757 | positive, the 1-bits in its binary representation are counted. |
| 1758 | If negative, the 0-bits in its two's-complement binary |
| 1759 | representation are counted. If zero, 0 is returned. |
| 1760 | |
| 1761 | @lisp |
| 1762 | (logcount #b10101010) |
| 1763 | @result{} 4 |
| 1764 | (logcount 0) |
| 1765 | @result{} 0 |
| 1766 | (logcount -2) |
| 1767 | @result{} 1 |
| 1768 | @end lisp |
| 1769 | @end deffn |
| 1770 | |
| 1771 | @deffn {Scheme Procedure} integer-length n |
| 1772 | @deffnx {C Function} scm_integer_length (n) |
| 1773 | Return the number of bits necessary to represent @var{n}. |
| 1774 | |
| 1775 | For positive @var{n} this is how many bits to the most significant one |
| 1776 | bit. For negative @var{n} it's how many bits to the most significant |
| 1777 | zero bit in twos complement form. |
| 1778 | |
| 1779 | @lisp |
| 1780 | (integer-length #b10101010) @result{} 8 |
| 1781 | (integer-length #b1111) @result{} 4 |
| 1782 | (integer-length 0) @result{} 0 |
| 1783 | (integer-length -1) @result{} 0 |
| 1784 | (integer-length -256) @result{} 8 |
| 1785 | (integer-length -257) @result{} 9 |
| 1786 | @end lisp |
| 1787 | @end deffn |
| 1788 | |
| 1789 | @deffn {Scheme Procedure} integer-expt n k |
| 1790 | @deffnx {C Function} scm_integer_expt (n, k) |
| 1791 | Return @var{n} raised to the power @var{k}. @var{k} must be an exact |
| 1792 | integer, @var{n} can be any number. |
| 1793 | |
| 1794 | Negative @var{k} is supported, and results in @m{1/n^|k|, 1/n^abs(k)} |
| 1795 | in the usual way. @math{@var{n}^0} is 1, as usual, and that includes |
| 1796 | @math{0^0} is 1. |
| 1797 | |
| 1798 | @lisp |
| 1799 | (integer-expt 2 5) @result{} 32 |
| 1800 | (integer-expt -3 3) @result{} -27 |
| 1801 | (integer-expt 5 -3) @result{} 1/125 |
| 1802 | (integer-expt 0 0) @result{} 1 |
| 1803 | @end lisp |
| 1804 | @end deffn |
| 1805 | |
| 1806 | @deffn {Scheme Procedure} bit-extract n start end |
| 1807 | @deffnx {C Function} scm_bit_extract (n, start, end) |
| 1808 | Return the integer composed of the @var{start} (inclusive) |
| 1809 | through @var{end} (exclusive) bits of @var{n}. The |
| 1810 | @var{start}th bit becomes the 0-th bit in the result. |
| 1811 | |
| 1812 | @lisp |
| 1813 | (number->string (bit-extract #b1101101010 0 4) 2) |
| 1814 | @result{} "1010" |
| 1815 | (number->string (bit-extract #b1101101010 4 9) 2) |
| 1816 | @result{} "10110" |
| 1817 | @end lisp |
| 1818 | @end deffn |
| 1819 | |
| 1820 | |
| 1821 | @node Random |
| 1822 | @subsubsection Random Number Generation |
| 1823 | |
| 1824 | Pseudo-random numbers are generated from a random state object, which |
| 1825 | can be created with @code{seed->random-state} or |
| 1826 | @code{datum->random-state}. An external representation (i.e.@: one |
| 1827 | which can written with @code{write} and read with @code{read}) of a |
| 1828 | random state object can be obtained via |
| 1829 | @code{random-state->datum}. The @var{state} parameter to the |
| 1830 | various functions below is optional, it defaults to the state object |
| 1831 | in the @code{*random-state*} variable. |
| 1832 | |
| 1833 | @deffn {Scheme Procedure} copy-random-state [state] |
| 1834 | @deffnx {C Function} scm_copy_random_state (state) |
| 1835 | Return a copy of the random state @var{state}. |
| 1836 | @end deffn |
| 1837 | |
| 1838 | @deffn {Scheme Procedure} random n [state] |
| 1839 | @deffnx {C Function} scm_random (n, state) |
| 1840 | Return a number in [0, @var{n}). |
| 1841 | |
| 1842 | Accepts a positive integer or real n and returns a |
| 1843 | number of the same type between zero (inclusive) and |
| 1844 | @var{n} (exclusive). The values returned have a uniform |
| 1845 | distribution. |
| 1846 | @end deffn |
| 1847 | |
| 1848 | @deffn {Scheme Procedure} random:exp [state] |
| 1849 | @deffnx {C Function} scm_random_exp (state) |
| 1850 | Return an inexact real in an exponential distribution with mean |
| 1851 | 1. For an exponential distribution with mean @var{u} use @code{(* |
| 1852 | @var{u} (random:exp))}. |
| 1853 | @end deffn |
| 1854 | |
| 1855 | @deffn {Scheme Procedure} random:hollow-sphere! vect [state] |
| 1856 | @deffnx {C Function} scm_random_hollow_sphere_x (vect, state) |
| 1857 | Fills @var{vect} with inexact real random numbers the sum of whose |
| 1858 | squares is equal to 1.0. Thinking of @var{vect} as coordinates in |
| 1859 | space of dimension @var{n} @math{=} @code{(vector-length @var{vect})}, |
| 1860 | the coordinates are uniformly distributed over the surface of the unit |
| 1861 | n-sphere. |
| 1862 | @end deffn |
| 1863 | |
| 1864 | @deffn {Scheme Procedure} random:normal [state] |
| 1865 | @deffnx {C Function} scm_random_normal (state) |
| 1866 | Return an inexact real in a normal distribution. The distribution |
| 1867 | used has mean 0 and standard deviation 1. For a normal distribution |
| 1868 | with mean @var{m} and standard deviation @var{d} use @code{(+ @var{m} |
| 1869 | (* @var{d} (random:normal)))}. |
| 1870 | @end deffn |
| 1871 | |
| 1872 | @deffn {Scheme Procedure} random:normal-vector! vect [state] |
| 1873 | @deffnx {C Function} scm_random_normal_vector_x (vect, state) |
| 1874 | Fills @var{vect} with inexact real random numbers that are |
| 1875 | independent and standard normally distributed |
| 1876 | (i.e., with mean 0 and variance 1). |
| 1877 | @end deffn |
| 1878 | |
| 1879 | @deffn {Scheme Procedure} random:solid-sphere! vect [state] |
| 1880 | @deffnx {C Function} scm_random_solid_sphere_x (vect, state) |
| 1881 | Fills @var{vect} with inexact real random numbers the sum of whose |
| 1882 | squares is less than 1.0. Thinking of @var{vect} as coordinates in |
| 1883 | space of dimension @var{n} @math{=} @code{(vector-length @var{vect})}, |
| 1884 | the coordinates are uniformly distributed within the unit |
| 1885 | @var{n}-sphere. |
| 1886 | @c FIXME: What does this mean, particularly the n-sphere part? |
| 1887 | @end deffn |
| 1888 | |
| 1889 | @deffn {Scheme Procedure} random:uniform [state] |
| 1890 | @deffnx {C Function} scm_random_uniform (state) |
| 1891 | Return a uniformly distributed inexact real random number in |
| 1892 | [0,1). |
| 1893 | @end deffn |
| 1894 | |
| 1895 | @deffn {Scheme Procedure} seed->random-state seed |
| 1896 | @deffnx {C Function} scm_seed_to_random_state (seed) |
| 1897 | Return a new random state using @var{seed}. |
| 1898 | @end deffn |
| 1899 | |
| 1900 | @deffn {Scheme Procedure} datum->random-state datum |
| 1901 | @deffnx {C Function} scm_datum_to_random_state (datum) |
| 1902 | Return a new random state from @var{datum}, which should have been |
| 1903 | obtained by @code{random-state->datum}. |
| 1904 | @end deffn |
| 1905 | |
| 1906 | @deffn {Scheme Procedure} random-state->datum state |
| 1907 | @deffnx {C Function} scm_random_state_to_datum (state) |
| 1908 | Return a datum representation of @var{state} that may be written out and |
| 1909 | read back with the Scheme reader. |
| 1910 | @end deffn |
| 1911 | |
| 1912 | @deffn {Scheme Procedure} random-state-from-platform |
| 1913 | @deffnx {C Function} scm_random_state_from_platform () |
| 1914 | Construct a new random state seeded from a platform-specific source of |
| 1915 | entropy, appropriate for use in non-security-critical applications. |
| 1916 | Currently @file{/dev/urandom} is tried first, or else the seed is based |
| 1917 | on the time, date, process ID, an address from a freshly allocated heap |
| 1918 | cell, an address from the local stack frame, and a high-resolution timer |
| 1919 | if available. |
| 1920 | @end deffn |
| 1921 | |
| 1922 | @defvar *random-state* |
| 1923 | The global random state used by the above functions when the |
| 1924 | @var{state} parameter is not given. |
| 1925 | @end defvar |
| 1926 | |
| 1927 | Note that the initial value of @code{*random-state*} is the same every |
| 1928 | time Guile starts up. Therefore, if you don't pass a @var{state} |
| 1929 | parameter to the above procedures, and you don't set |
| 1930 | @code{*random-state*} to @code{(seed->random-state your-seed)}, where |
| 1931 | @code{your-seed} is something that @emph{isn't} the same every time, |
| 1932 | you'll get the same sequence of ``random'' numbers on every run. |
| 1933 | |
| 1934 | For example, unless the relevant source code has changed, @code{(map |
| 1935 | random (cdr (iota 30)))}, if the first use of random numbers since |
| 1936 | Guile started up, will always give: |
| 1937 | |
| 1938 | @lisp |
| 1939 | (map random (cdr (iota 19))) |
| 1940 | @result{} |
| 1941 | (0 1 1 2 2 2 1 2 6 7 10 0 5 3 12 5 5 12) |
| 1942 | @end lisp |
| 1943 | |
| 1944 | To seed the random state in a sensible way for non-security-critical |
| 1945 | applications, do this during initialization of your program: |
| 1946 | |
| 1947 | @lisp |
| 1948 | (set! *random-state* (random-state-from-platform)) |
| 1949 | @end lisp |
| 1950 | |
| 1951 | |
| 1952 | @node Characters |
| 1953 | @subsection Characters |
| 1954 | @tpindex Characters |
| 1955 | |
| 1956 | In Scheme, there is a data type to describe a single character. |
| 1957 | |
| 1958 | Defining what exactly a character @emph{is} can be more complicated |
| 1959 | than it seems. Guile follows the advice of R6RS and uses The Unicode |
| 1960 | Standard to help define what a character is. So, for Guile, a |
| 1961 | character is anything in the Unicode Character Database. |
| 1962 | |
| 1963 | @cindex code point |
| 1964 | @cindex Unicode code point |
| 1965 | |
| 1966 | The Unicode Character Database is basically a table of characters |
| 1967 | indexed using integers called 'code points'. Valid code points are in |
| 1968 | the ranges 0 to @code{#xD7FF} inclusive or @code{#xE000} to |
| 1969 | @code{#x10FFFF} inclusive, which is about 1.1 million code points. |
| 1970 | |
| 1971 | @cindex designated code point |
| 1972 | @cindex code point, designated |
| 1973 | |
| 1974 | Any code point that has been assigned to a character or that has |
| 1975 | otherwise been given a meaning by Unicode is called a 'designated code |
| 1976 | point'. Most of the designated code points, about 200,000 of them, |
| 1977 | indicate characters, accents or other combining marks that modify |
| 1978 | other characters, symbols, whitespace, and control characters. Some |
| 1979 | are not characters but indicators that suggest how to format or |
| 1980 | display neighboring characters. |
| 1981 | |
| 1982 | @cindex reserved code point |
| 1983 | @cindex code point, reserved |
| 1984 | |
| 1985 | If a code point is not a designated code point -- if it has not been |
| 1986 | assigned to a character by The Unicode Standard -- it is a 'reserved |
| 1987 | code point', meaning that they are reserved for future use. Most of |
| 1988 | the code points, about 800,000, are 'reserved code points'. |
| 1989 | |
| 1990 | By convention, a Unicode code point is written as |
| 1991 | ``U+XXXX'' where ``XXXX'' is a hexadecimal number. Please note that |
| 1992 | this convenient notation is not valid code. Guile does not interpret |
| 1993 | ``U+XXXX'' as a character. |
| 1994 | |
| 1995 | In Scheme, a character literal is written as @code{#\@var{name}} where |
| 1996 | @var{name} is the name of the character that you want. Printable |
| 1997 | characters have their usual single character name; for example, |
| 1998 | @code{#\a} is a lower case @code{a}. |
| 1999 | |
| 2000 | Some of the code points are 'combining characters' that are not meant |
| 2001 | to be printed by themselves but are instead meant to modify the |
| 2002 | appearance of the previous character. For combining characters, an |
| 2003 | alternate form of the character literal is @code{#\} followed by |
| 2004 | U+25CC (a small, dotted circle), followed by the combining character. |
| 2005 | This allows the combining character to be drawn on the circle, not on |
| 2006 | the backslash of @code{#\}. |
| 2007 | |
| 2008 | Many of the non-printing characters, such as whitespace characters and |
| 2009 | control characters, also have names. |
| 2010 | |
| 2011 | The most commonly used non-printing characters have long character |
| 2012 | names, described in the table below. |
| 2013 | |
| 2014 | @multitable {@code{#\backspace}} {Preferred} |
| 2015 | @item Character Name @tab Codepoint |
| 2016 | @item @code{#\nul} @tab U+0000 |
| 2017 | @item @code{#\alarm} @tab u+0007 |
| 2018 | @item @code{#\backspace} @tab U+0008 |
| 2019 | @item @code{#\tab} @tab U+0009 |
| 2020 | @item @code{#\linefeed} @tab U+000A |
| 2021 | @item @code{#\newline} @tab U+000A |
| 2022 | @item @code{#\vtab} @tab U+000B |
| 2023 | @item @code{#\page} @tab U+000C |
| 2024 | @item @code{#\return} @tab U+000D |
| 2025 | @item @code{#\esc} @tab U+001B |
| 2026 | @item @code{#\space} @tab U+0020 |
| 2027 | @item @code{#\delete} @tab U+007F |
| 2028 | @end multitable |
| 2029 | |
| 2030 | There are also short names for all of the ``C0 control characters'' |
| 2031 | (those with code points below 32). The following table lists the short |
| 2032 | name for each character. |
| 2033 | |
| 2034 | @multitable @columnfractions .25 .25 .25 .25 |
| 2035 | @item 0 = @code{#\nul} |
| 2036 | @tab 1 = @code{#\soh} |
| 2037 | @tab 2 = @code{#\stx} |
| 2038 | @tab 3 = @code{#\etx} |
| 2039 | @item 4 = @code{#\eot} |
| 2040 | @tab 5 = @code{#\enq} |
| 2041 | @tab 6 = @code{#\ack} |
| 2042 | @tab 7 = @code{#\bel} |
| 2043 | @item 8 = @code{#\bs} |
| 2044 | @tab 9 = @code{#\ht} |
| 2045 | @tab 10 = @code{#\lf} |
| 2046 | @tab 11 = @code{#\vt} |
| 2047 | @item 12 = @code{#\ff} |
| 2048 | @tab 13 = @code{#\cr} |
| 2049 | @tab 14 = @code{#\so} |
| 2050 | @tab 15 = @code{#\si} |
| 2051 | @item 16 = @code{#\dle} |
| 2052 | @tab 17 = @code{#\dc1} |
| 2053 | @tab 18 = @code{#\dc2} |
| 2054 | @tab 19 = @code{#\dc3} |
| 2055 | @item 20 = @code{#\dc4} |
| 2056 | @tab 21 = @code{#\nak} |
| 2057 | @tab 22 = @code{#\syn} |
| 2058 | @tab 23 = @code{#\etb} |
| 2059 | @item 24 = @code{#\can} |
| 2060 | @tab 25 = @code{#\em} |
| 2061 | @tab 26 = @code{#\sub} |
| 2062 | @tab 27 = @code{#\esc} |
| 2063 | @item 28 = @code{#\fs} |
| 2064 | @tab 29 = @code{#\gs} |
| 2065 | @tab 30 = @code{#\rs} |
| 2066 | @tab 31 = @code{#\us} |
| 2067 | @item 32 = @code{#\sp} |
| 2068 | @end multitable |
| 2069 | |
| 2070 | The short name for the ``delete'' character (code point U+007F) is |
| 2071 | @code{#\del}. |
| 2072 | |
| 2073 | The R7RS name for the ``escape'' character (code point U+001B) is |
| 2074 | @code{#\escape}. |
| 2075 | |
| 2076 | There are also a few alternative names left over for compatibility with |
| 2077 | previous versions of Guile. |
| 2078 | |
| 2079 | @multitable {@code{#\backspace}} {Preferred} |
| 2080 | @item Alternate @tab Standard |
| 2081 | @item @code{#\nl} @tab @code{#\newline} |
| 2082 | @item @code{#\np} @tab @code{#\page} |
| 2083 | @item @code{#\null} @tab @code{#\nul} |
| 2084 | @end multitable |
| 2085 | |
| 2086 | Characters may also be written using their code point values. They can |
| 2087 | be written with as an octal number, such as @code{#\10} for |
| 2088 | @code{#\bs} or @code{#\177} for @code{#\del}. |
| 2089 | |
| 2090 | If one prefers hex to octal, there is an additional syntax for character |
| 2091 | escapes: @code{#\xHHHH} -- the letter 'x' followed by a hexadecimal |
| 2092 | number of one to eight digits. |
| 2093 | |
| 2094 | @rnindex char? |
| 2095 | @deffn {Scheme Procedure} char? x |
| 2096 | @deffnx {C Function} scm_char_p (x) |
| 2097 | Return @code{#t} if @var{x} is a character, else @code{#f}. |
| 2098 | @end deffn |
| 2099 | |
| 2100 | Fundamentally, the character comparison operations below are |
| 2101 | numeric comparisons of the character's code points. |
| 2102 | |
| 2103 | @rnindex char=? |
| 2104 | @deffn {Scheme Procedure} char=? x y |
| 2105 | Return @code{#t} if code point of @var{x} is equal to the code point |
| 2106 | of @var{y}, else @code{#f}. |
| 2107 | @end deffn |
| 2108 | |
| 2109 | @rnindex char<? |
| 2110 | @deffn {Scheme Procedure} char<? x y |
| 2111 | Return @code{#t} if the code point of @var{x} is less than the code |
| 2112 | point of @var{y}, else @code{#f}. |
| 2113 | @end deffn |
| 2114 | |
| 2115 | @rnindex char<=? |
| 2116 | @deffn {Scheme Procedure} char<=? x y |
| 2117 | Return @code{#t} if the code point of @var{x} is less than or equal |
| 2118 | to the code point of @var{y}, else @code{#f}. |
| 2119 | @end deffn |
| 2120 | |
| 2121 | @rnindex char>? |
| 2122 | @deffn {Scheme Procedure} char>? x y |
| 2123 | Return @code{#t} if the code point of @var{x} is greater than the |
| 2124 | code point of @var{y}, else @code{#f}. |
| 2125 | @end deffn |
| 2126 | |
| 2127 | @rnindex char>=? |
| 2128 | @deffn {Scheme Procedure} char>=? x y |
| 2129 | Return @code{#t} if the code point of @var{x} is greater than or |
| 2130 | equal to the code point of @var{y}, else @code{#f}. |
| 2131 | @end deffn |
| 2132 | |
| 2133 | @cindex case folding |
| 2134 | |
| 2135 | Case-insensitive character comparisons use @emph{Unicode case |
| 2136 | folding}. In case folding comparisons, if a character is lowercase |
| 2137 | and has an uppercase form that can be expressed as a single character, |
| 2138 | it is converted to uppercase before comparison. All other characters |
| 2139 | undergo no conversion before the comparison occurs. This includes the |
| 2140 | German sharp S (Eszett) which is not uppercased before conversion |
| 2141 | because its uppercase form has two characters. Unicode case folding |
| 2142 | is language independent: it uses rules that are generally true, but, |
| 2143 | it cannot cover all cases for all languages. |
| 2144 | |
| 2145 | @rnindex char-ci=? |
| 2146 | @deffn {Scheme Procedure} char-ci=? x y |
| 2147 | Return @code{#t} if the case-folded code point of @var{x} is the same |
| 2148 | as the case-folded code point of @var{y}, else @code{#f}. |
| 2149 | @end deffn |
| 2150 | |
| 2151 | @rnindex char-ci<? |
| 2152 | @deffn {Scheme Procedure} char-ci<? x y |
| 2153 | Return @code{#t} if the case-folded code point of @var{x} is less |
| 2154 | than the case-folded code point of @var{y}, else @code{#f}. |
| 2155 | @end deffn |
| 2156 | |
| 2157 | @rnindex char-ci<=? |
| 2158 | @deffn {Scheme Procedure} char-ci<=? x y |
| 2159 | Return @code{#t} if the case-folded code point of @var{x} is less |
| 2160 | than or equal to the case-folded code point of @var{y}, else |
| 2161 | @code{#f}. |
| 2162 | @end deffn |
| 2163 | |
| 2164 | @rnindex char-ci>? |
| 2165 | @deffn {Scheme Procedure} char-ci>? x y |
| 2166 | Return @code{#t} if the case-folded code point of @var{x} is greater |
| 2167 | than the case-folded code point of @var{y}, else @code{#f}. |
| 2168 | @end deffn |
| 2169 | |
| 2170 | @rnindex char-ci>=? |
| 2171 | @deffn {Scheme Procedure} char-ci>=? x y |
| 2172 | Return @code{#t} if the case-folded code point of @var{x} is greater |
| 2173 | than or equal to the case-folded code point of @var{y}, else |
| 2174 | @code{#f}. |
| 2175 | @end deffn |
| 2176 | |
| 2177 | @rnindex char-alphabetic? |
| 2178 | @deffn {Scheme Procedure} char-alphabetic? chr |
| 2179 | @deffnx {C Function} scm_char_alphabetic_p (chr) |
| 2180 | Return @code{#t} if @var{chr} is alphabetic, else @code{#f}. |
| 2181 | @end deffn |
| 2182 | |
| 2183 | @rnindex char-numeric? |
| 2184 | @deffn {Scheme Procedure} char-numeric? chr |
| 2185 | @deffnx {C Function} scm_char_numeric_p (chr) |
| 2186 | Return @code{#t} if @var{chr} is numeric, else @code{#f}. |
| 2187 | @end deffn |
| 2188 | |
| 2189 | @rnindex char-whitespace? |
| 2190 | @deffn {Scheme Procedure} char-whitespace? chr |
| 2191 | @deffnx {C Function} scm_char_whitespace_p (chr) |
| 2192 | Return @code{#t} if @var{chr} is whitespace, else @code{#f}. |
| 2193 | @end deffn |
| 2194 | |
| 2195 | @rnindex char-upper-case? |
| 2196 | @deffn {Scheme Procedure} char-upper-case? chr |
| 2197 | @deffnx {C Function} scm_char_upper_case_p (chr) |
| 2198 | Return @code{#t} if @var{chr} is uppercase, else @code{#f}. |
| 2199 | @end deffn |
| 2200 | |
| 2201 | @rnindex char-lower-case? |
| 2202 | @deffn {Scheme Procedure} char-lower-case? chr |
| 2203 | @deffnx {C Function} scm_char_lower_case_p (chr) |
| 2204 | Return @code{#t} if @var{chr} is lowercase, else @code{#f}. |
| 2205 | @end deffn |
| 2206 | |
| 2207 | @deffn {Scheme Procedure} char-is-both? chr |
| 2208 | @deffnx {C Function} scm_char_is_both_p (chr) |
| 2209 | Return @code{#t} if @var{chr} is either uppercase or lowercase, else |
| 2210 | @code{#f}. |
| 2211 | @end deffn |
| 2212 | |
| 2213 | @deffn {Scheme Procedure} char-general-category chr |
| 2214 | @deffnx {C Function} scm_char_general_category (chr) |
| 2215 | Return a symbol giving the two-letter name of the Unicode general |
| 2216 | category assigned to @var{chr} or @code{#f} if no named category is |
| 2217 | assigned. The following table provides a list of category names along |
| 2218 | with their meanings. |
| 2219 | |
| 2220 | @multitable @columnfractions .1 .4 .1 .4 |
| 2221 | @item Lu |
| 2222 | @tab Uppercase letter |
| 2223 | @tab Pf |
| 2224 | @tab Final quote punctuation |
| 2225 | @item Ll |
| 2226 | @tab Lowercase letter |
| 2227 | @tab Po |
| 2228 | @tab Other punctuation |
| 2229 | @item Lt |
| 2230 | @tab Titlecase letter |
| 2231 | @tab Sm |
| 2232 | @tab Math symbol |
| 2233 | @item Lm |
| 2234 | @tab Modifier letter |
| 2235 | @tab Sc |
| 2236 | @tab Currency symbol |
| 2237 | @item Lo |
| 2238 | @tab Other letter |
| 2239 | @tab Sk |
| 2240 | @tab Modifier symbol |
| 2241 | @item Mn |
| 2242 | @tab Non-spacing mark |
| 2243 | @tab So |
| 2244 | @tab Other symbol |
| 2245 | @item Mc |
| 2246 | @tab Combining spacing mark |
| 2247 | @tab Zs |
| 2248 | @tab Space separator |
| 2249 | @item Me |
| 2250 | @tab Enclosing mark |
| 2251 | @tab Zl |
| 2252 | @tab Line separator |
| 2253 | @item Nd |
| 2254 | @tab Decimal digit number |
| 2255 | @tab Zp |
| 2256 | @tab Paragraph separator |
| 2257 | @item Nl |
| 2258 | @tab Letter number |
| 2259 | @tab Cc |
| 2260 | @tab Control |
| 2261 | @item No |
| 2262 | @tab Other number |
| 2263 | @tab Cf |
| 2264 | @tab Format |
| 2265 | @item Pc |
| 2266 | @tab Connector punctuation |
| 2267 | @tab Cs |
| 2268 | @tab Surrogate |
| 2269 | @item Pd |
| 2270 | @tab Dash punctuation |
| 2271 | @tab Co |
| 2272 | @tab Private use |
| 2273 | @item Ps |
| 2274 | @tab Open punctuation |
| 2275 | @tab Cn |
| 2276 | @tab Unassigned |
| 2277 | @item Pe |
| 2278 | @tab Close punctuation |
| 2279 | @tab |
| 2280 | @tab |
| 2281 | @item Pi |
| 2282 | @tab Initial quote punctuation |
| 2283 | @tab |
| 2284 | @tab |
| 2285 | @end multitable |
| 2286 | @end deffn |
| 2287 | |
| 2288 | @rnindex char->integer |
| 2289 | @deffn {Scheme Procedure} char->integer chr |
| 2290 | @deffnx {C Function} scm_char_to_integer (chr) |
| 2291 | Return the code point of @var{chr}. |
| 2292 | @end deffn |
| 2293 | |
| 2294 | @rnindex integer->char |
| 2295 | @deffn {Scheme Procedure} integer->char n |
| 2296 | @deffnx {C Function} scm_integer_to_char (n) |
| 2297 | Return the character that has code point @var{n}. The integer @var{n} |
| 2298 | must be a valid code point. Valid code points are in the ranges 0 to |
| 2299 | @code{#xD7FF} inclusive or @code{#xE000} to @code{#x10FFFF} inclusive. |
| 2300 | @end deffn |
| 2301 | |
| 2302 | @rnindex char-upcase |
| 2303 | @deffn {Scheme Procedure} char-upcase chr |
| 2304 | @deffnx {C Function} scm_char_upcase (chr) |
| 2305 | Return the uppercase character version of @var{chr}. |
| 2306 | @end deffn |
| 2307 | |
| 2308 | @rnindex char-downcase |
| 2309 | @deffn {Scheme Procedure} char-downcase chr |
| 2310 | @deffnx {C Function} scm_char_downcase (chr) |
| 2311 | Return the lowercase character version of @var{chr}. |
| 2312 | @end deffn |
| 2313 | |
| 2314 | @rnindex char-titlecase |
| 2315 | @deffn {Scheme Procedure} char-titlecase chr |
| 2316 | @deffnx {C Function} scm_char_titlecase (chr) |
| 2317 | Return the titlecase character version of @var{chr} if one exists; |
| 2318 | otherwise return the uppercase version. |
| 2319 | |
| 2320 | For most characters these will be the same, but the Unicode Standard |
| 2321 | includes certain digraph compatibility characters, such as @code{U+01F3} |
| 2322 | ``dz'', for which the uppercase and titlecase characters are different |
| 2323 | (@code{U+01F1} ``DZ'' and @code{U+01F2} ``Dz'' in this case, |
| 2324 | respectively). |
| 2325 | @end deffn |
| 2326 | |
| 2327 | @tindex scm_t_wchar |
| 2328 | @deftypefn {C Function} scm_t_wchar scm_c_upcase (scm_t_wchar @var{c}) |
| 2329 | @deftypefnx {C Function} scm_t_wchar scm_c_downcase (scm_t_wchar @var{c}) |
| 2330 | @deftypefnx {C Function} scm_t_wchar scm_c_titlecase (scm_t_wchar @var{c}) |
| 2331 | |
| 2332 | These C functions take an integer representation of a Unicode |
| 2333 | codepoint and return the codepoint corresponding to its uppercase, |
| 2334 | lowercase, and titlecase forms respectively. The type |
| 2335 | @code{scm_t_wchar} is a signed, 32-bit integer. |
| 2336 | @end deftypefn |
| 2337 | |
| 2338 | Characters also have ``formal names'', which are defined by Unicode. |
| 2339 | These names can be accessed in Guile from the @code{(ice-9 unicode)} |
| 2340 | module: |
| 2341 | |
| 2342 | @example |
| 2343 | (use-modules (ice-9 unicode)) |
| 2344 | @end example |
| 2345 | |
| 2346 | @deffn {Scheme Procedure} char->formal-name chr |
| 2347 | Return the formal all-upper-case Unicode name of @var{ch}, |
| 2348 | as a string, or @code{#f} if the character has no name. |
| 2349 | @end deffn |
| 2350 | |
| 2351 | @deffn {Scheme Procedure} formal-name->char name |
| 2352 | Return the character whose formal all-upper-case Unicode name is |
| 2353 | @var{name}, or @code{#f} if no such character is known. |
| 2354 | @end deffn |
| 2355 | |
| 2356 | @node Character Sets |
| 2357 | @subsection Character Sets |
| 2358 | |
| 2359 | The features described in this section correspond directly to SRFI-14. |
| 2360 | |
| 2361 | The data type @dfn{charset} implements sets of characters |
| 2362 | (@pxref{Characters}). Because the internal representation of |
| 2363 | character sets is not visible to the user, a lot of procedures for |
| 2364 | handling them are provided. |
| 2365 | |
| 2366 | Character sets can be created, extended, tested for the membership of a |
| 2367 | characters and be compared to other character sets. |
| 2368 | |
| 2369 | @menu |
| 2370 | * Character Set Predicates/Comparison:: |
| 2371 | * Iterating Over Character Sets:: Enumerate charset elements. |
| 2372 | * Creating Character Sets:: Making new charsets. |
| 2373 | * Querying Character Sets:: Test charsets for membership etc. |
| 2374 | * Character-Set Algebra:: Calculating new charsets. |
| 2375 | * Standard Character Sets:: Variables containing predefined charsets. |
| 2376 | @end menu |
| 2377 | |
| 2378 | @node Character Set Predicates/Comparison |
| 2379 | @subsubsection Character Set Predicates/Comparison |
| 2380 | |
| 2381 | Use these procedures for testing whether an object is a character set, |
| 2382 | or whether several character sets are equal or subsets of each other. |
| 2383 | @code{char-set-hash} can be used for calculating a hash value, maybe for |
| 2384 | usage in fast lookup procedures. |
| 2385 | |
| 2386 | @deffn {Scheme Procedure} char-set? obj |
| 2387 | @deffnx {C Function} scm_char_set_p (obj) |
| 2388 | Return @code{#t} if @var{obj} is a character set, @code{#f} |
| 2389 | otherwise. |
| 2390 | @end deffn |
| 2391 | |
| 2392 | @deffn {Scheme Procedure} char-set= char_set @dots{} |
| 2393 | @deffnx {C Function} scm_char_set_eq (char_sets) |
| 2394 | Return @code{#t} if all given character sets are equal. |
| 2395 | @end deffn |
| 2396 | |
| 2397 | @deffn {Scheme Procedure} char-set<= char_set @dots{} |
| 2398 | @deffnx {C Function} scm_char_set_leq (char_sets) |
| 2399 | Return @code{#t} if every character set @var{char_set}i is a subset |
| 2400 | of character set @var{char_set}i+1. |
| 2401 | @end deffn |
| 2402 | |
| 2403 | @deffn {Scheme Procedure} char-set-hash cs [bound] |
| 2404 | @deffnx {C Function} scm_char_set_hash (cs, bound) |
| 2405 | Compute a hash value for the character set @var{cs}. If |
| 2406 | @var{bound} is given and non-zero, it restricts the |
| 2407 | returned value to the range 0 @dots{} @var{bound} - 1. |
| 2408 | @end deffn |
| 2409 | |
| 2410 | @c =================================================================== |
| 2411 | |
| 2412 | @node Iterating Over Character Sets |
| 2413 | @subsubsection Iterating Over Character Sets |
| 2414 | |
| 2415 | Character set cursors are a means for iterating over the members of a |
| 2416 | character sets. After creating a character set cursor with |
| 2417 | @code{char-set-cursor}, a cursor can be dereferenced with |
| 2418 | @code{char-set-ref}, advanced to the next member with |
| 2419 | @code{char-set-cursor-next}. Whether a cursor has passed past the last |
| 2420 | element of the set can be checked with @code{end-of-char-set?}. |
| 2421 | |
| 2422 | Additionally, mapping and (un-)folding procedures for character sets are |
| 2423 | provided. |
| 2424 | |
| 2425 | @deffn {Scheme Procedure} char-set-cursor cs |
| 2426 | @deffnx {C Function} scm_char_set_cursor (cs) |
| 2427 | Return a cursor into the character set @var{cs}. |
| 2428 | @end deffn |
| 2429 | |
| 2430 | @deffn {Scheme Procedure} char-set-ref cs cursor |
| 2431 | @deffnx {C Function} scm_char_set_ref (cs, cursor) |
| 2432 | Return the character at the current cursor position |
| 2433 | @var{cursor} in the character set @var{cs}. It is an error to |
| 2434 | pass a cursor for which @code{end-of-char-set?} returns true. |
| 2435 | @end deffn |
| 2436 | |
| 2437 | @deffn {Scheme Procedure} char-set-cursor-next cs cursor |
| 2438 | @deffnx {C Function} scm_char_set_cursor_next (cs, cursor) |
| 2439 | Advance the character set cursor @var{cursor} to the next |
| 2440 | character in the character set @var{cs}. It is an error if the |
| 2441 | cursor given satisfies @code{end-of-char-set?}. |
| 2442 | @end deffn |
| 2443 | |
| 2444 | @deffn {Scheme Procedure} end-of-char-set? cursor |
| 2445 | @deffnx {C Function} scm_end_of_char_set_p (cursor) |
| 2446 | Return @code{#t} if @var{cursor} has reached the end of a |
| 2447 | character set, @code{#f} otherwise. |
| 2448 | @end deffn |
| 2449 | |
| 2450 | @deffn {Scheme Procedure} char-set-fold kons knil cs |
| 2451 | @deffnx {C Function} scm_char_set_fold (kons, knil, cs) |
| 2452 | Fold the procedure @var{kons} over the character set @var{cs}, |
| 2453 | initializing it with @var{knil}. |
| 2454 | @end deffn |
| 2455 | |
| 2456 | @deffn {Scheme Procedure} char-set-unfold p f g seed [base_cs] |
| 2457 | @deffnx {C Function} scm_char_set_unfold (p, f, g, seed, base_cs) |
| 2458 | This is a fundamental constructor for character sets. |
| 2459 | @itemize @bullet |
| 2460 | @item @var{g} is used to generate a series of ``seed'' values |
| 2461 | from the initial seed: @var{seed}, (@var{g} @var{seed}), |
| 2462 | (@var{g}^2 @var{seed}), (@var{g}^3 @var{seed}), @dots{} |
| 2463 | @item @var{p} tells us when to stop -- when it returns true |
| 2464 | when applied to one of the seed values. |
| 2465 | @item @var{f} maps each seed value to a character. These |
| 2466 | characters are added to the base character set @var{base_cs} to |
| 2467 | form the result; @var{base_cs} defaults to the empty set. |
| 2468 | @end itemize |
| 2469 | @end deffn |
| 2470 | |
| 2471 | @deffn {Scheme Procedure} char-set-unfold! p f g seed base_cs |
| 2472 | @deffnx {C Function} scm_char_set_unfold_x (p, f, g, seed, base_cs) |
| 2473 | This is a fundamental constructor for character sets. |
| 2474 | @itemize @bullet |
| 2475 | @item @var{g} is used to generate a series of ``seed'' values |
| 2476 | from the initial seed: @var{seed}, (@var{g} @var{seed}), |
| 2477 | (@var{g}^2 @var{seed}), (@var{g}^3 @var{seed}), @dots{} |
| 2478 | @item @var{p} tells us when to stop -- when it returns true |
| 2479 | when applied to one of the seed values. |
| 2480 | @item @var{f} maps each seed value to a character. These |
| 2481 | characters are added to the base character set @var{base_cs} to |
| 2482 | form the result; @var{base_cs} defaults to the empty set. |
| 2483 | @end itemize |
| 2484 | @end deffn |
| 2485 | |
| 2486 | @deffn {Scheme Procedure} char-set-for-each proc cs |
| 2487 | @deffnx {C Function} scm_char_set_for_each (proc, cs) |
| 2488 | Apply @var{proc} to every character in the character set |
| 2489 | @var{cs}. The return value is not specified. |
| 2490 | @end deffn |
| 2491 | |
| 2492 | @deffn {Scheme Procedure} char-set-map proc cs |
| 2493 | @deffnx {C Function} scm_char_set_map (proc, cs) |
| 2494 | Map the procedure @var{proc} over every character in @var{cs}. |
| 2495 | @var{proc} must be a character -> character procedure. |
| 2496 | @end deffn |
| 2497 | |
| 2498 | @c =================================================================== |
| 2499 | |
| 2500 | @node Creating Character Sets |
| 2501 | @subsubsection Creating Character Sets |
| 2502 | |
| 2503 | New character sets are produced with these procedures. |
| 2504 | |
| 2505 | @deffn {Scheme Procedure} char-set-copy cs |
| 2506 | @deffnx {C Function} scm_char_set_copy (cs) |
| 2507 | Return a newly allocated character set containing all |
| 2508 | characters in @var{cs}. |
| 2509 | @end deffn |
| 2510 | |
| 2511 | @deffn {Scheme Procedure} char-set chr @dots{} |
| 2512 | @deffnx {C Function} scm_char_set (chrs) |
| 2513 | Return a character set containing all given characters. |
| 2514 | @end deffn |
| 2515 | |
| 2516 | @deffn {Scheme Procedure} list->char-set list [base_cs] |
| 2517 | @deffnx {C Function} scm_list_to_char_set (list, base_cs) |
| 2518 | Convert the character list @var{list} to a character set. If |
| 2519 | the character set @var{base_cs} is given, the character in this |
| 2520 | set are also included in the result. |
| 2521 | @end deffn |
| 2522 | |
| 2523 | @deffn {Scheme Procedure} list->char-set! list base_cs |
| 2524 | @deffnx {C Function} scm_list_to_char_set_x (list, base_cs) |
| 2525 | Convert the character list @var{list} to a character set. The |
| 2526 | characters are added to @var{base_cs} and @var{base_cs} is |
| 2527 | returned. |
| 2528 | @end deffn |
| 2529 | |
| 2530 | @deffn {Scheme Procedure} string->char-set str [base_cs] |
| 2531 | @deffnx {C Function} scm_string_to_char_set (str, base_cs) |
| 2532 | Convert the string @var{str} to a character set. If the |
| 2533 | character set @var{base_cs} is given, the characters in this |
| 2534 | set are also included in the result. |
| 2535 | @end deffn |
| 2536 | |
| 2537 | @deffn {Scheme Procedure} string->char-set! str base_cs |
| 2538 | @deffnx {C Function} scm_string_to_char_set_x (str, base_cs) |
| 2539 | Convert the string @var{str} to a character set. The |
| 2540 | characters from the string are added to @var{base_cs}, and |
| 2541 | @var{base_cs} is returned. |
| 2542 | @end deffn |
| 2543 | |
| 2544 | @deffn {Scheme Procedure} char-set-filter pred cs [base_cs] |
| 2545 | @deffnx {C Function} scm_char_set_filter (pred, cs, base_cs) |
| 2546 | Return a character set containing every character from @var{cs} |
| 2547 | so that it satisfies @var{pred}. If provided, the characters |
| 2548 | from @var{base_cs} are added to the result. |
| 2549 | @end deffn |
| 2550 | |
| 2551 | @deffn {Scheme Procedure} char-set-filter! pred cs base_cs |
| 2552 | @deffnx {C Function} scm_char_set_filter_x (pred, cs, base_cs) |
| 2553 | Return a character set containing every character from @var{cs} |
| 2554 | so that it satisfies @var{pred}. The characters are added to |
| 2555 | @var{base_cs} and @var{base_cs} is returned. |
| 2556 | @end deffn |
| 2557 | |
| 2558 | @deffn {Scheme Procedure} ucs-range->char-set lower upper [error [base_cs]] |
| 2559 | @deffnx {C Function} scm_ucs_range_to_char_set (lower, upper, error, base_cs) |
| 2560 | Return a character set containing all characters whose |
| 2561 | character codes lie in the half-open range |
| 2562 | [@var{lower},@var{upper}). |
| 2563 | |
| 2564 | If @var{error} is a true value, an error is signalled if the |
| 2565 | specified range contains characters which are not contained in |
| 2566 | the implemented character range. If @var{error} is @code{#f}, |
| 2567 | these characters are silently left out of the resulting |
| 2568 | character set. |
| 2569 | |
| 2570 | The characters in @var{base_cs} are added to the result, if |
| 2571 | given. |
| 2572 | @end deffn |
| 2573 | |
| 2574 | @deffn {Scheme Procedure} ucs-range->char-set! lower upper error base_cs |
| 2575 | @deffnx {C Function} scm_ucs_range_to_char_set_x (lower, upper, error, base_cs) |
| 2576 | Return a character set containing all characters whose |
| 2577 | character codes lie in the half-open range |
| 2578 | [@var{lower},@var{upper}). |
| 2579 | |
| 2580 | If @var{error} is a true value, an error is signalled if the |
| 2581 | specified range contains characters which are not contained in |
| 2582 | the implemented character range. If @var{error} is @code{#f}, |
| 2583 | these characters are silently left out of the resulting |
| 2584 | character set. |
| 2585 | |
| 2586 | The characters are added to @var{base_cs} and @var{base_cs} is |
| 2587 | returned. |
| 2588 | @end deffn |
| 2589 | |
| 2590 | @deffn {Scheme Procedure} ->char-set x |
| 2591 | @deffnx {C Function} scm_to_char_set (x) |
| 2592 | Coerces x into a char-set. @var{x} may be a string, character or |
| 2593 | char-set. A string is converted to the set of its constituent |
| 2594 | characters; a character is converted to a singleton set; a char-set is |
| 2595 | returned as-is. |
| 2596 | @end deffn |
| 2597 | |
| 2598 | @c =================================================================== |
| 2599 | |
| 2600 | @node Querying Character Sets |
| 2601 | @subsubsection Querying Character Sets |
| 2602 | |
| 2603 | Access the elements and other information of a character set with these |
| 2604 | procedures. |
| 2605 | |
| 2606 | @deffn {Scheme Procedure} %char-set-dump cs |
| 2607 | Returns an association list containing debugging information |
| 2608 | for @var{cs}. The association list has the following entries. |
| 2609 | @table @code |
| 2610 | @item char-set |
| 2611 | The char-set itself |
| 2612 | @item len |
| 2613 | The number of groups of contiguous code points the char-set |
| 2614 | contains |
| 2615 | @item ranges |
| 2616 | A list of lists where each sublist is a range of code points |
| 2617 | and their associated characters |
| 2618 | @end table |
| 2619 | The return value of this function cannot be relied upon to be |
| 2620 | consistent between versions of Guile and should not be used in code. |
| 2621 | @end deffn |
| 2622 | |
| 2623 | @deffn {Scheme Procedure} char-set-size cs |
| 2624 | @deffnx {C Function} scm_char_set_size (cs) |
| 2625 | Return the number of elements in character set @var{cs}. |
| 2626 | @end deffn |
| 2627 | |
| 2628 | @deffn {Scheme Procedure} char-set-count pred cs |
| 2629 | @deffnx {C Function} scm_char_set_count (pred, cs) |
| 2630 | Return the number of the elements int the character set |
| 2631 | @var{cs} which satisfy the predicate @var{pred}. |
| 2632 | @end deffn |
| 2633 | |
| 2634 | @deffn {Scheme Procedure} char-set->list cs |
| 2635 | @deffnx {C Function} scm_char_set_to_list (cs) |
| 2636 | Return a list containing the elements of the character set |
| 2637 | @var{cs}. |
| 2638 | @end deffn |
| 2639 | |
| 2640 | @deffn {Scheme Procedure} char-set->string cs |
| 2641 | @deffnx {C Function} scm_char_set_to_string (cs) |
| 2642 | Return a string containing the elements of the character set |
| 2643 | @var{cs}. The order in which the characters are placed in the |
| 2644 | string is not defined. |
| 2645 | @end deffn |
| 2646 | |
| 2647 | @deffn {Scheme Procedure} char-set-contains? cs ch |
| 2648 | @deffnx {C Function} scm_char_set_contains_p (cs, ch) |
| 2649 | Return @code{#t} if the character @var{ch} is contained in the |
| 2650 | character set @var{cs}, or @code{#f} otherwise. |
| 2651 | @end deffn |
| 2652 | |
| 2653 | @deffn {Scheme Procedure} char-set-every pred cs |
| 2654 | @deffnx {C Function} scm_char_set_every (pred, cs) |
| 2655 | Return a true value if every character in the character set |
| 2656 | @var{cs} satisfies the predicate @var{pred}. |
| 2657 | @end deffn |
| 2658 | |
| 2659 | @deffn {Scheme Procedure} char-set-any pred cs |
| 2660 | @deffnx {C Function} scm_char_set_any (pred, cs) |
| 2661 | Return a true value if any character in the character set |
| 2662 | @var{cs} satisfies the predicate @var{pred}. |
| 2663 | @end deffn |
| 2664 | |
| 2665 | @c =================================================================== |
| 2666 | |
| 2667 | @node Character-Set Algebra |
| 2668 | @subsubsection Character-Set Algebra |
| 2669 | |
| 2670 | Character sets can be manipulated with the common set algebra operation, |
| 2671 | such as union, complement, intersection etc. All of these procedures |
| 2672 | provide side-effecting variants, which modify their character set |
| 2673 | argument(s). |
| 2674 | |
| 2675 | @deffn {Scheme Procedure} char-set-adjoin cs chr @dots{} |
| 2676 | @deffnx {C Function} scm_char_set_adjoin (cs, chrs) |
| 2677 | Add all character arguments to the first argument, which must |
| 2678 | be a character set. |
| 2679 | @end deffn |
| 2680 | |
| 2681 | @deffn {Scheme Procedure} char-set-delete cs chr @dots{} |
| 2682 | @deffnx {C Function} scm_char_set_delete (cs, chrs) |
| 2683 | Delete all character arguments from the first argument, which |
| 2684 | must be a character set. |
| 2685 | @end deffn |
| 2686 | |
| 2687 | @deffn {Scheme Procedure} char-set-adjoin! cs chr @dots{} |
| 2688 | @deffnx {C Function} scm_char_set_adjoin_x (cs, chrs) |
| 2689 | Add all character arguments to the first argument, which must |
| 2690 | be a character set. |
| 2691 | @end deffn |
| 2692 | |
| 2693 | @deffn {Scheme Procedure} char-set-delete! cs chr @dots{} |
| 2694 | @deffnx {C Function} scm_char_set_delete_x (cs, chrs) |
| 2695 | Delete all character arguments from the first argument, which |
| 2696 | must be a character set. |
| 2697 | @end deffn |
| 2698 | |
| 2699 | @deffn {Scheme Procedure} char-set-complement cs |
| 2700 | @deffnx {C Function} scm_char_set_complement (cs) |
| 2701 | Return the complement of the character set @var{cs}. |
| 2702 | @end deffn |
| 2703 | |
| 2704 | Note that the complement of a character set is likely to contain many |
| 2705 | reserved code points (code points that are not associated with |
| 2706 | characters). It may be helpful to modify the output of |
| 2707 | @code{char-set-complement} by computing its intersection with the set |
| 2708 | of designated code points, @code{char-set:designated}. |
| 2709 | |
| 2710 | @deffn {Scheme Procedure} char-set-union cs @dots{} |
| 2711 | @deffnx {C Function} scm_char_set_union (char_sets) |
| 2712 | Return the union of all argument character sets. |
| 2713 | @end deffn |
| 2714 | |
| 2715 | @deffn {Scheme Procedure} char-set-intersection cs @dots{} |
| 2716 | @deffnx {C Function} scm_char_set_intersection (char_sets) |
| 2717 | Return the intersection of all argument character sets. |
| 2718 | @end deffn |
| 2719 | |
| 2720 | @deffn {Scheme Procedure} char-set-difference cs1 cs @dots{} |
| 2721 | @deffnx {C Function} scm_char_set_difference (cs1, char_sets) |
| 2722 | Return the difference of all argument character sets. |
| 2723 | @end deffn |
| 2724 | |
| 2725 | @deffn {Scheme Procedure} char-set-xor cs @dots{} |
| 2726 | @deffnx {C Function} scm_char_set_xor (char_sets) |
| 2727 | Return the exclusive-or of all argument character sets. |
| 2728 | @end deffn |
| 2729 | |
| 2730 | @deffn {Scheme Procedure} char-set-diff+intersection cs1 cs @dots{} |
| 2731 | @deffnx {C Function} scm_char_set_diff_plus_intersection (cs1, char_sets) |
| 2732 | Return the difference and the intersection of all argument |
| 2733 | character sets. |
| 2734 | @end deffn |
| 2735 | |
| 2736 | @deffn {Scheme Procedure} char-set-complement! cs |
| 2737 | @deffnx {C Function} scm_char_set_complement_x (cs) |
| 2738 | Return the complement of the character set @var{cs}. |
| 2739 | @end deffn |
| 2740 | |
| 2741 | @deffn {Scheme Procedure} char-set-union! cs1 cs @dots{} |
| 2742 | @deffnx {C Function} scm_char_set_union_x (cs1, char_sets) |
| 2743 | Return the union of all argument character sets. |
| 2744 | @end deffn |
| 2745 | |
| 2746 | @deffn {Scheme Procedure} char-set-intersection! cs1 cs @dots{} |
| 2747 | @deffnx {C Function} scm_char_set_intersection_x (cs1, char_sets) |
| 2748 | Return the intersection of all argument character sets. |
| 2749 | @end deffn |
| 2750 | |
| 2751 | @deffn {Scheme Procedure} char-set-difference! cs1 cs @dots{} |
| 2752 | @deffnx {C Function} scm_char_set_difference_x (cs1, char_sets) |
| 2753 | Return the difference of all argument character sets. |
| 2754 | @end deffn |
| 2755 | |
| 2756 | @deffn {Scheme Procedure} char-set-xor! cs1 cs @dots{} |
| 2757 | @deffnx {C Function} scm_char_set_xor_x (cs1, char_sets) |
| 2758 | Return the exclusive-or of all argument character sets. |
| 2759 | @end deffn |
| 2760 | |
| 2761 | @deffn {Scheme Procedure} char-set-diff+intersection! cs1 cs2 cs @dots{} |
| 2762 | @deffnx {C Function} scm_char_set_diff_plus_intersection_x (cs1, cs2, char_sets) |
| 2763 | Return the difference and the intersection of all argument |
| 2764 | character sets. |
| 2765 | @end deffn |
| 2766 | |
| 2767 | @c =================================================================== |
| 2768 | |
| 2769 | @node Standard Character Sets |
| 2770 | @subsubsection Standard Character Sets |
| 2771 | |
| 2772 | In order to make the use of the character set data type and procedures |
| 2773 | useful, several predefined character set variables exist. |
| 2774 | |
| 2775 | @cindex codeset |
| 2776 | @cindex charset |
| 2777 | @cindex locale |
| 2778 | |
| 2779 | These character sets are locale independent and are not recomputed |
| 2780 | upon a @code{setlocale} call. They contain characters from the whole |
| 2781 | range of Unicode code points. For instance, @code{char-set:letter} |
| 2782 | contains about 100,000 characters. |
| 2783 | |
| 2784 | @defvr {Scheme Variable} char-set:lower-case |
| 2785 | @defvrx {C Variable} scm_char_set_lower_case |
| 2786 | All lower-case characters. |
| 2787 | @end defvr |
| 2788 | |
| 2789 | @defvr {Scheme Variable} char-set:upper-case |
| 2790 | @defvrx {C Variable} scm_char_set_upper_case |
| 2791 | All upper-case characters. |
| 2792 | @end defvr |
| 2793 | |
| 2794 | @defvr {Scheme Variable} char-set:title-case |
| 2795 | @defvrx {C Variable} scm_char_set_title_case |
| 2796 | All single characters that function as if they were an upper-case |
| 2797 | letter followed by a lower-case letter. |
| 2798 | @end defvr |
| 2799 | |
| 2800 | @defvr {Scheme Variable} char-set:letter |
| 2801 | @defvrx {C Variable} scm_char_set_letter |
| 2802 | All letters. This includes @code{char-set:lower-case}, |
| 2803 | @code{char-set:upper-case}, @code{char-set:title-case}, and many |
| 2804 | letters that have no case at all. For example, Chinese and Japanese |
| 2805 | characters typically have no concept of case. |
| 2806 | @end defvr |
| 2807 | |
| 2808 | @defvr {Scheme Variable} char-set:digit |
| 2809 | @defvrx {C Variable} scm_char_set_digit |
| 2810 | All digits. |
| 2811 | @end defvr |
| 2812 | |
| 2813 | @defvr {Scheme Variable} char-set:letter+digit |
| 2814 | @defvrx {C Variable} scm_char_set_letter_and_digit |
| 2815 | The union of @code{char-set:letter} and @code{char-set:digit}. |
| 2816 | @end defvr |
| 2817 | |
| 2818 | @defvr {Scheme Variable} char-set:graphic |
| 2819 | @defvrx {C Variable} scm_char_set_graphic |
| 2820 | All characters which would put ink on the paper. |
| 2821 | @end defvr |
| 2822 | |
| 2823 | @defvr {Scheme Variable} char-set:printing |
| 2824 | @defvrx {C Variable} scm_char_set_printing |
| 2825 | The union of @code{char-set:graphic} and @code{char-set:whitespace}. |
| 2826 | @end defvr |
| 2827 | |
| 2828 | @defvr {Scheme Variable} char-set:whitespace |
| 2829 | @defvrx {C Variable} scm_char_set_whitespace |
| 2830 | All whitespace characters. |
| 2831 | @end defvr |
| 2832 | |
| 2833 | @defvr {Scheme Variable} char-set:blank |
| 2834 | @defvrx {C Variable} scm_char_set_blank |
| 2835 | All horizontal whitespace characters, which notably includes |
| 2836 | @code{#\space} and @code{#\tab}. |
| 2837 | @end defvr |
| 2838 | |
| 2839 | @defvr {Scheme Variable} char-set:iso-control |
| 2840 | @defvrx {C Variable} scm_char_set_iso_control |
| 2841 | The ISO control characters are the C0 control characters (U+0000 to |
| 2842 | U+001F), delete (U+007F), and the C1 control characters (U+0080 to |
| 2843 | U+009F). |
| 2844 | @end defvr |
| 2845 | |
| 2846 | @defvr {Scheme Variable} char-set:punctuation |
| 2847 | @defvrx {C Variable} scm_char_set_punctuation |
| 2848 | All punctuation characters, such as the characters |
| 2849 | @code{!"#%&'()*,-./:;?@@[\\]_@{@}} |
| 2850 | @end defvr |
| 2851 | |
| 2852 | @defvr {Scheme Variable} char-set:symbol |
| 2853 | @defvrx {C Variable} scm_char_set_symbol |
| 2854 | All symbol characters, such as the characters @code{$+<=>^`|~}. |
| 2855 | @end defvr |
| 2856 | |
| 2857 | @defvr {Scheme Variable} char-set:hex-digit |
| 2858 | @defvrx {C Variable} scm_char_set_hex_digit |
| 2859 | The hexadecimal digits @code{0123456789abcdefABCDEF}. |
| 2860 | @end defvr |
| 2861 | |
| 2862 | @defvr {Scheme Variable} char-set:ascii |
| 2863 | @defvrx {C Variable} scm_char_set_ascii |
| 2864 | All ASCII characters. |
| 2865 | @end defvr |
| 2866 | |
| 2867 | @defvr {Scheme Variable} char-set:empty |
| 2868 | @defvrx {C Variable} scm_char_set_empty |
| 2869 | The empty character set. |
| 2870 | @end defvr |
| 2871 | |
| 2872 | @defvr {Scheme Variable} char-set:designated |
| 2873 | @defvrx {C Variable} scm_char_set_designated |
| 2874 | This character set contains all designated code points. This includes |
| 2875 | all the code points to which Unicode has assigned a character or other |
| 2876 | meaning. |
| 2877 | @end defvr |
| 2878 | |
| 2879 | @defvr {Scheme Variable} char-set:full |
| 2880 | @defvrx {C Variable} scm_char_set_full |
| 2881 | This character set contains all possible code points. This includes |
| 2882 | both designated and reserved code points. |
| 2883 | @end defvr |
| 2884 | |
| 2885 | @node Strings |
| 2886 | @subsection Strings |
| 2887 | @tpindex Strings |
| 2888 | |
| 2889 | Strings are fixed-length sequences of characters. They can be created |
| 2890 | by calling constructor procedures, but they can also literally get |
| 2891 | entered at the @acronym{REPL} or in Scheme source files. |
| 2892 | |
| 2893 | @c Guile provides a rich set of string processing procedures, because text |
| 2894 | @c handling is very important when Guile is used as a scripting language. |
| 2895 | |
| 2896 | Strings always carry the information about how many characters they are |
| 2897 | composed of with them, so there is no special end-of-string character, |
| 2898 | like in C. That means that Scheme strings can contain any character, |
| 2899 | even the @samp{#\nul} character @samp{\0}. |
| 2900 | |
| 2901 | To use strings efficiently, you need to know a bit about how Guile |
| 2902 | implements them. In Guile, a string consists of two parts, a head and |
| 2903 | the actual memory where the characters are stored. When a string (or |
| 2904 | a substring of it) is copied, only a new head gets created, the memory |
| 2905 | is usually not copied. The two heads start out pointing to the same |
| 2906 | memory. |
| 2907 | |
| 2908 | When one of these two strings is modified, as with @code{string-set!}, |
| 2909 | their common memory does get copied so that each string has its own |
| 2910 | memory and modifying one does not accidentally modify the other as well. |
| 2911 | Thus, Guile's strings are `copy on write'; the actual copying of their |
| 2912 | memory is delayed until one string is written to. |
| 2913 | |
| 2914 | This implementation makes functions like @code{substring} very |
| 2915 | efficient in the common case that no modifications are done to the |
| 2916 | involved strings. |
| 2917 | |
| 2918 | If you do know that your strings are getting modified right away, you |
| 2919 | can use @code{substring/copy} instead of @code{substring}. This |
| 2920 | function performs the copy immediately at the time of creation. This |
| 2921 | is more efficient, especially in a multi-threaded program. Also, |
| 2922 | @code{substring/copy} can avoid the problem that a short substring |
| 2923 | holds on to the memory of a very large original string that could |
| 2924 | otherwise be recycled. |
| 2925 | |
| 2926 | If you want to avoid the copy altogether, so that modifications of one |
| 2927 | string show up in the other, you can use @code{substring/shared}. The |
| 2928 | strings created by this procedure are called @dfn{mutation sharing |
| 2929 | substrings} since the substring and the original string share |
| 2930 | modifications to each other. |
| 2931 | |
| 2932 | If you want to prevent modifications, use @code{substring/read-only}. |
| 2933 | |
| 2934 | Guile provides all procedures of SRFI-13 and a few more. |
| 2935 | |
| 2936 | @menu |
| 2937 | * String Syntax:: Read syntax for strings. |
| 2938 | * String Predicates:: Testing strings for certain properties. |
| 2939 | * String Constructors:: Creating new string objects. |
| 2940 | * List/String Conversion:: Converting from/to lists of characters. |
| 2941 | * String Selection:: Select portions from strings. |
| 2942 | * String Modification:: Modify parts or whole strings. |
| 2943 | * String Comparison:: Lexicographic ordering predicates. |
| 2944 | * String Searching:: Searching in strings. |
| 2945 | * Alphabetic Case Mapping:: Convert the alphabetic case of strings. |
| 2946 | * Reversing and Appending Strings:: Appending strings to form a new string. |
| 2947 | * Mapping Folding and Unfolding:: Iterating over strings. |
| 2948 | * Miscellaneous String Operations:: Replicating, insertion, parsing, ... |
| 2949 | * Representing Strings as Bytes:: Encoding and decoding strings. |
| 2950 | * Conversion to/from C:: |
| 2951 | * String Internals:: The storage strategy for strings. |
| 2952 | @end menu |
| 2953 | |
| 2954 | @node String Syntax |
| 2955 | @subsubsection String Read Syntax |
| 2956 | |
| 2957 | @c In the following @code is used to get a good font in TeX etc, but |
| 2958 | @c is omitted for Info format, so as not to risk any confusion over |
| 2959 | @c whether surrounding ` ' quotes are part of the escape or are |
| 2960 | @c special in a string (they're not). |
| 2961 | |
| 2962 | The read syntax for strings is an arbitrarily long sequence of |
| 2963 | characters enclosed in double quotes (@nicode{"}). |
| 2964 | |
| 2965 | Backslash is an escape character and can be used to insert the following |
| 2966 | special characters. @nicode{\"} and @nicode{\\} are R5RS standard, |
| 2967 | @nicode{\|} is R7RS standard, the next seven are R6RS standard --- |
| 2968 | notice they follow C syntax --- and the remaining four are Guile |
| 2969 | extensions. |
| 2970 | |
| 2971 | @table @asis |
| 2972 | @item @nicode{\\} |
| 2973 | Backslash character. |
| 2974 | |
| 2975 | @item @nicode{\"} |
| 2976 | Double quote character (an unescaped @nicode{"} is otherwise the end |
| 2977 | of the string). |
| 2978 | |
| 2979 | @item @nicode{\|} |
| 2980 | Vertical bar character. |
| 2981 | |
| 2982 | @item @nicode{\a} |
| 2983 | Bell character (ASCII 7). |
| 2984 | |
| 2985 | @item @nicode{\f} |
| 2986 | Formfeed character (ASCII 12). |
| 2987 | |
| 2988 | @item @nicode{\n} |
| 2989 | Newline character (ASCII 10). |
| 2990 | |
| 2991 | @item @nicode{\r} |
| 2992 | Carriage return character (ASCII 13). |
| 2993 | |
| 2994 | @item @nicode{\t} |
| 2995 | Tab character (ASCII 9). |
| 2996 | |
| 2997 | @item @nicode{\v} |
| 2998 | Vertical tab character (ASCII 11). |
| 2999 | |
| 3000 | @item @nicode{\b} |
| 3001 | Backspace character (ASCII 8). |
| 3002 | |
| 3003 | @item @nicode{\0} |
| 3004 | NUL character (ASCII 0). |
| 3005 | |
| 3006 | @item @nicode{\(} |
| 3007 | Open parenthesis. This is intended for use at the beginning of lines in |
| 3008 | multiline strings to avoid confusing Emacs lisp modes. |
| 3009 | |
| 3010 | @item @nicode{\} followed by newline (ASCII 10) |
| 3011 | Nothing. This way if @nicode{\} is the last character in a line, the |
| 3012 | string will continue with the first character from the next line, |
| 3013 | without a line break. |
| 3014 | |
| 3015 | If the @code{hungry-eol-escapes} reader option is enabled, which is not |
| 3016 | the case by default, leading whitespace on the next line is discarded. |
| 3017 | |
| 3018 | @lisp |
| 3019 | "foo\ |
| 3020 | bar" |
| 3021 | @result{} "foo bar" |
| 3022 | (read-enable 'hungry-eol-escapes) |
| 3023 | "foo\ |
| 3024 | bar" |
| 3025 | @result{} "foobar" |
| 3026 | @end lisp |
| 3027 | @item @nicode{\xHH} |
| 3028 | Character code given by two hexadecimal digits. For example |
| 3029 | @nicode{\x7f} for an ASCII DEL (127). |
| 3030 | |
| 3031 | @item @nicode{\uHHHH} |
| 3032 | Character code given by four hexadecimal digits. For example |
| 3033 | @nicode{\u0100} for a capital A with macron (U+0100). |
| 3034 | |
| 3035 | @item @nicode{\UHHHHHH} |
| 3036 | Character code given by six hexadecimal digits. For example |
| 3037 | @nicode{\U010402}. |
| 3038 | @end table |
| 3039 | |
| 3040 | @noindent |
| 3041 | The following are examples of string literals: |
| 3042 | |
| 3043 | @lisp |
| 3044 | "foo" |
| 3045 | "bar plonk" |
| 3046 | "Hello World" |
| 3047 | "\"Hi\", he said." |
| 3048 | @end lisp |
| 3049 | |
| 3050 | The three escape sequences @code{\xHH}, @code{\uHHHH} and @code{\UHHHHHH} were |
| 3051 | chosen to not break compatibility with code written for previous versions of |
| 3052 | Guile. The R6RS specification suggests a different, incompatible syntax for hex |
| 3053 | escapes: @code{\xHHHH;} -- a character code followed by one to eight hexadecimal |
| 3054 | digits terminated with a semicolon. If this escape format is desired instead, |
| 3055 | it can be enabled with the reader option @code{r6rs-hex-escapes}. |
| 3056 | |
| 3057 | @lisp |
| 3058 | (read-enable 'r6rs-hex-escapes) |
| 3059 | @end lisp |
| 3060 | |
| 3061 | For more on reader options, @xref{Scheme Read}. |
| 3062 | |
| 3063 | @node String Predicates |
| 3064 | @subsubsection String Predicates |
| 3065 | |
| 3066 | The following procedures can be used to check whether a given string |
| 3067 | fulfills some specified property. |
| 3068 | |
| 3069 | @rnindex string? |
| 3070 | @deffn {Scheme Procedure} string? obj |
| 3071 | @deffnx {C Function} scm_string_p (obj) |
| 3072 | Return @code{#t} if @var{obj} is a string, else @code{#f}. |
| 3073 | @end deffn |
| 3074 | |
| 3075 | @deftypefn {C Function} int scm_is_string (SCM obj) |
| 3076 | Returns @code{1} if @var{obj} is a string, @code{0} otherwise. |
| 3077 | @end deftypefn |
| 3078 | |
| 3079 | @deffn {Scheme Procedure} string-null? str |
| 3080 | @deffnx {C Function} scm_string_null_p (str) |
| 3081 | Return @code{#t} if @var{str}'s length is zero, and |
| 3082 | @code{#f} otherwise. |
| 3083 | @lisp |
| 3084 | (string-null? "") @result{} #t |
| 3085 | y @result{} "foo" |
| 3086 | (string-null? y) @result{} #f |
| 3087 | @end lisp |
| 3088 | @end deffn |
| 3089 | |
| 3090 | @deffn {Scheme Procedure} string-any char_pred s [start [end]] |
| 3091 | @deffnx {C Function} scm_string_any (char_pred, s, start, end) |
| 3092 | Check if @var{char_pred} is true for any character in string @var{s}. |
| 3093 | |
| 3094 | @var{char_pred} can be a character to check for any equal to that, or |
| 3095 | a character set (@pxref{Character Sets}) to check for any in that set, |
| 3096 | or a predicate procedure to call. |
| 3097 | |
| 3098 | For a procedure, calls @code{(@var{char_pred} c)} are made |
| 3099 | successively on the characters from @var{start} to @var{end}. If |
| 3100 | @var{char_pred} returns true (ie.@: non-@code{#f}), @code{string-any} |
| 3101 | stops and that return value is the return from @code{string-any}. The |
| 3102 | call on the last character (ie.@: at @math{@var{end}-1}), if that |
| 3103 | point is reached, is a tail call. |
| 3104 | |
| 3105 | If there are no characters in @var{s} (ie.@: @var{start} equals |
| 3106 | @var{end}) then the return is @code{#f}. |
| 3107 | @end deffn |
| 3108 | |
| 3109 | @deffn {Scheme Procedure} string-every char_pred s [start [end]] |
| 3110 | @deffnx {C Function} scm_string_every (char_pred, s, start, end) |
| 3111 | Check if @var{char_pred} is true for every character in string |
| 3112 | @var{s}. |
| 3113 | |
| 3114 | @var{char_pred} can be a character to check for every character equal |
| 3115 | to that, or a character set (@pxref{Character Sets}) to check for |
| 3116 | every character being in that set, or a predicate procedure to call. |
| 3117 | |
| 3118 | For a procedure, calls @code{(@var{char_pred} c)} are made |
| 3119 | successively on the characters from @var{start} to @var{end}. If |
| 3120 | @var{char_pred} returns @code{#f}, @code{string-every} stops and |
| 3121 | returns @code{#f}. The call on the last character (ie.@: at |
| 3122 | @math{@var{end}-1}), if that point is reached, is a tail call and the |
| 3123 | return from that call is the return from @code{string-every}. |
| 3124 | |
| 3125 | If there are no characters in @var{s} (ie.@: @var{start} equals |
| 3126 | @var{end}) then the return is @code{#t}. |
| 3127 | @end deffn |
| 3128 | |
| 3129 | @node String Constructors |
| 3130 | @subsubsection String Constructors |
| 3131 | |
| 3132 | The string constructor procedures create new string objects, possibly |
| 3133 | initializing them with some specified character data. See also |
| 3134 | @xref{String Selection}, for ways to create strings from existing |
| 3135 | strings. |
| 3136 | |
| 3137 | @c FIXME::martin: list->string belongs into `List/String Conversion' |
| 3138 | |
| 3139 | @deffn {Scheme Procedure} string char@dots{} |
| 3140 | @rnindex string |
| 3141 | Return a newly allocated string made from the given character |
| 3142 | arguments. |
| 3143 | |
| 3144 | @example |
| 3145 | (string #\x #\y #\z) @result{} "xyz" |
| 3146 | (string) @result{} "" |
| 3147 | @end example |
| 3148 | @end deffn |
| 3149 | |
| 3150 | @deffn {Scheme Procedure} list->string lst |
| 3151 | @deffnx {C Function} scm_string (lst) |
| 3152 | @rnindex list->string |
| 3153 | Return a newly allocated string made from a list of characters. |
| 3154 | |
| 3155 | @example |
| 3156 | (list->string '(#\a #\b #\c)) @result{} "abc" |
| 3157 | @end example |
| 3158 | @end deffn |
| 3159 | |
| 3160 | @deffn {Scheme Procedure} reverse-list->string lst |
| 3161 | @deffnx {C Function} scm_reverse_list_to_string (lst) |
| 3162 | Return a newly allocated string made from a list of characters, in |
| 3163 | reverse order. |
| 3164 | |
| 3165 | @example |
| 3166 | (reverse-list->string '(#\a #\B #\c)) @result{} "cBa" |
| 3167 | @end example |
| 3168 | @end deffn |
| 3169 | |
| 3170 | @rnindex make-string |
| 3171 | @deffn {Scheme Procedure} make-string k [chr] |
| 3172 | @deffnx {C Function} scm_make_string (k, chr) |
| 3173 | Return a newly allocated string of |
| 3174 | length @var{k}. If @var{chr} is given, then all elements of |
| 3175 | the string are initialized to @var{chr}, otherwise the contents |
| 3176 | of the string are unspecified. |
| 3177 | @end deffn |
| 3178 | |
| 3179 | @deftypefn {C Function} SCM scm_c_make_string (size_t len, SCM chr) |
| 3180 | Like @code{scm_make_string}, but expects the length as a |
| 3181 | @code{size_t}. |
| 3182 | @end deftypefn |
| 3183 | |
| 3184 | @deffn {Scheme Procedure} string-tabulate proc len |
| 3185 | @deffnx {C Function} scm_string_tabulate (proc, len) |
| 3186 | @var{proc} is an integer->char procedure. Construct a string |
| 3187 | of size @var{len} by applying @var{proc} to each index to |
| 3188 | produce the corresponding string element. The order in which |
| 3189 | @var{proc} is applied to the indices is not specified. |
| 3190 | @end deffn |
| 3191 | |
| 3192 | @deffn {Scheme Procedure} string-join ls [delimiter [grammar]] |
| 3193 | @deffnx {C Function} scm_string_join (ls, delimiter, grammar) |
| 3194 | Append the string in the string list @var{ls}, using the string |
| 3195 | @var{delimiter} as a delimiter between the elements of @var{ls}. |
| 3196 | @var{grammar} is a symbol which specifies how the delimiter is |
| 3197 | placed between the strings, and defaults to the symbol |
| 3198 | @code{infix}. |
| 3199 | |
| 3200 | @table @code |
| 3201 | @item infix |
| 3202 | Insert the separator between list elements. An empty string |
| 3203 | will produce an empty list. |
| 3204 | @item strict-infix |
| 3205 | Like @code{infix}, but will raise an error if given the empty |
| 3206 | list. |
| 3207 | @item suffix |
| 3208 | Insert the separator after every list element. |
| 3209 | @item prefix |
| 3210 | Insert the separator before each list element. |
| 3211 | @end table |
| 3212 | @end deffn |
| 3213 | |
| 3214 | @node List/String Conversion |
| 3215 | @subsubsection List/String conversion |
| 3216 | |
| 3217 | When processing strings, it is often convenient to first convert them |
| 3218 | into a list representation by using the procedure @code{string->list}, |
| 3219 | work with the resulting list, and then convert it back into a string. |
| 3220 | These procedures are useful for similar tasks. |
| 3221 | |
| 3222 | @rnindex string->list |
| 3223 | @deffn {Scheme Procedure} string->list str [start [end]] |
| 3224 | @deffnx {C Function} scm_substring_to_list (str, start, end) |
| 3225 | @deffnx {C Function} scm_string_to_list (str) |
| 3226 | Convert the string @var{str} into a list of characters. |
| 3227 | @end deffn |
| 3228 | |
| 3229 | @deffn {Scheme Procedure} string-split str char_pred |
| 3230 | @deffnx {C Function} scm_string_split (str, char_pred) |
| 3231 | Split the string @var{str} into a list of substrings delimited |
| 3232 | by appearances of characters that |
| 3233 | |
| 3234 | @itemize @bullet |
| 3235 | @item |
| 3236 | equal @var{char_pred}, if it is a character, |
| 3237 | |
| 3238 | @item |
| 3239 | satisfy the predicate @var{char_pred}, if it is a procedure, |
| 3240 | |
| 3241 | @item |
| 3242 | are in the set @var{char_pred}, if it is a character set. |
| 3243 | @end itemize |
| 3244 | |
| 3245 | Note that an empty substring between separator characters will result in |
| 3246 | an empty string in the result list. |
| 3247 | |
| 3248 | @lisp |
| 3249 | (string-split "root:x:0:0:root:/root:/bin/bash" #\:) |
| 3250 | @result{} |
| 3251 | ("root" "x" "0" "0" "root" "/root" "/bin/bash") |
| 3252 | |
| 3253 | (string-split "::" #\:) |
| 3254 | @result{} |
| 3255 | ("" "" "") |
| 3256 | |
| 3257 | (string-split "" #\:) |
| 3258 | @result{} |
| 3259 | ("") |
| 3260 | @end lisp |
| 3261 | @end deffn |
| 3262 | |
| 3263 | |
| 3264 | @node String Selection |
| 3265 | @subsubsection String Selection |
| 3266 | |
| 3267 | Portions of strings can be extracted by these procedures. |
| 3268 | @code{string-ref} delivers individual characters whereas |
| 3269 | @code{substring} can be used to extract substrings from longer strings. |
| 3270 | |
| 3271 | @rnindex string-length |
| 3272 | @deffn {Scheme Procedure} string-length string |
| 3273 | @deffnx {C Function} scm_string_length (string) |
| 3274 | Return the number of characters in @var{string}. |
| 3275 | @end deffn |
| 3276 | |
| 3277 | @deftypefn {C Function} size_t scm_c_string_length (SCM str) |
| 3278 | Return the number of characters in @var{str} as a @code{size_t}. |
| 3279 | @end deftypefn |
| 3280 | |
| 3281 | @rnindex string-ref |
| 3282 | @deffn {Scheme Procedure} string-ref str k |
| 3283 | @deffnx {C Function} scm_string_ref (str, k) |
| 3284 | Return character @var{k} of @var{str} using zero-origin |
| 3285 | indexing. @var{k} must be a valid index of @var{str}. |
| 3286 | @end deffn |
| 3287 | |
| 3288 | @deftypefn {C Function} SCM scm_c_string_ref (SCM str, size_t k) |
| 3289 | Return character @var{k} of @var{str} using zero-origin |
| 3290 | indexing. @var{k} must be a valid index of @var{str}. |
| 3291 | @end deftypefn |
| 3292 | |
| 3293 | @rnindex string-copy |
| 3294 | @deffn {Scheme Procedure} string-copy str [start [end]] |
| 3295 | @deffnx {C Function} scm_substring_copy (str, start, end) |
| 3296 | @deffnx {C Function} scm_string_copy (str) |
| 3297 | Return a copy of the given string @var{str}. |
| 3298 | |
| 3299 | The returned string shares storage with @var{str} initially, but it is |
| 3300 | copied as soon as one of the two strings is modified. |
| 3301 | @end deffn |
| 3302 | |
| 3303 | @rnindex substring |
| 3304 | @deffn {Scheme Procedure} substring str start [end] |
| 3305 | @deffnx {C Function} scm_substring (str, start, end) |
| 3306 | Return a new string formed from the characters |
| 3307 | of @var{str} beginning with index @var{start} (inclusive) and |
| 3308 | ending with index @var{end} (exclusive). |
| 3309 | @var{str} must be a string, @var{start} and @var{end} must be |
| 3310 | exact integers satisfying: |
| 3311 | |
| 3312 | 0 <= @var{start} <= @var{end} <= @code{(string-length @var{str})}. |
| 3313 | |
| 3314 | The returned string shares storage with @var{str} initially, but it is |
| 3315 | copied as soon as one of the two strings is modified. |
| 3316 | @end deffn |
| 3317 | |
| 3318 | @deffn {Scheme Procedure} substring/shared str start [end] |
| 3319 | @deffnx {C Function} scm_substring_shared (str, start, end) |
| 3320 | Like @code{substring}, but the strings continue to share their storage |
| 3321 | even if they are modified. Thus, modifications to @var{str} show up |
| 3322 | in the new string, and vice versa. |
| 3323 | @end deffn |
| 3324 | |
| 3325 | @deffn {Scheme Procedure} substring/copy str start [end] |
| 3326 | @deffnx {C Function} scm_substring_copy (str, start, end) |
| 3327 | Like @code{substring}, but the storage for the new string is copied |
| 3328 | immediately. |
| 3329 | @end deffn |
| 3330 | |
| 3331 | @deffn {Scheme Procedure} substring/read-only str start [end] |
| 3332 | @deffnx {C Function} scm_substring_read_only (str, start, end) |
| 3333 | Like @code{substring}, but the resulting string can not be modified. |
| 3334 | @end deffn |
| 3335 | |
| 3336 | @deftypefn {C Function} SCM scm_c_substring (SCM str, size_t start, size_t end) |
| 3337 | @deftypefnx {C Function} SCM scm_c_substring_shared (SCM str, size_t start, size_t end) |
| 3338 | @deftypefnx {C Function} SCM scm_c_substring_copy (SCM str, size_t start, size_t end) |
| 3339 | @deftypefnx {C Function} SCM scm_c_substring_read_only (SCM str, size_t start, size_t end) |
| 3340 | Like @code{scm_substring}, etc. but the bounds are given as a @code{size_t}. |
| 3341 | @end deftypefn |
| 3342 | |
| 3343 | @deffn {Scheme Procedure} string-take s n |
| 3344 | @deffnx {C Function} scm_string_take (s, n) |
| 3345 | Return the @var{n} first characters of @var{s}. |
| 3346 | @end deffn |
| 3347 | |
| 3348 | @deffn {Scheme Procedure} string-drop s n |
| 3349 | @deffnx {C Function} scm_string_drop (s, n) |
| 3350 | Return all but the first @var{n} characters of @var{s}. |
| 3351 | @end deffn |
| 3352 | |
| 3353 | @deffn {Scheme Procedure} string-take-right s n |
| 3354 | @deffnx {C Function} scm_string_take_right (s, n) |
| 3355 | Return the @var{n} last characters of @var{s}. |
| 3356 | @end deffn |
| 3357 | |
| 3358 | @deffn {Scheme Procedure} string-drop-right s n |
| 3359 | @deffnx {C Function} scm_string_drop_right (s, n) |
| 3360 | Return all but the last @var{n} characters of @var{s}. |
| 3361 | @end deffn |
| 3362 | |
| 3363 | @deffn {Scheme Procedure} string-pad s len [chr [start [end]]] |
| 3364 | @deffnx {Scheme Procedure} string-pad-right s len [chr [start [end]]] |
| 3365 | @deffnx {C Function} scm_string_pad (s, len, chr, start, end) |
| 3366 | @deffnx {C Function} scm_string_pad_right (s, len, chr, start, end) |
| 3367 | Take characters @var{start} to @var{end} from the string @var{s} and |
| 3368 | either pad with @var{chr} or truncate them to give @var{len} |
| 3369 | characters. |
| 3370 | |
| 3371 | @code{string-pad} pads or truncates on the left, so for example |
| 3372 | |
| 3373 | @example |
| 3374 | (string-pad "x" 3) @result{} " x" |
| 3375 | (string-pad "abcde" 3) @result{} "cde" |
| 3376 | @end example |
| 3377 | |
| 3378 | @code{string-pad-right} pads or truncates on the right, so for example |
| 3379 | |
| 3380 | @example |
| 3381 | (string-pad-right "x" 3) @result{} "x " |
| 3382 | (string-pad-right "abcde" 3) @result{} "abc" |
| 3383 | @end example |
| 3384 | @end deffn |
| 3385 | |
| 3386 | @deffn {Scheme Procedure} string-trim s [char_pred [start [end]]] |
| 3387 | @deffnx {Scheme Procedure} string-trim-right s [char_pred [start [end]]] |
| 3388 | @deffnx {Scheme Procedure} string-trim-both s [char_pred [start [end]]] |
| 3389 | @deffnx {C Function} scm_string_trim (s, char_pred, start, end) |
| 3390 | @deffnx {C Function} scm_string_trim_right (s, char_pred, start, end) |
| 3391 | @deffnx {C Function} scm_string_trim_both (s, char_pred, start, end) |
| 3392 | Trim occurrences of @var{char_pred} from the ends of @var{s}. |
| 3393 | |
| 3394 | @code{string-trim} trims @var{char_pred} characters from the left |
| 3395 | (start) of the string, @code{string-trim-right} trims them from the |
| 3396 | right (end) of the string, @code{string-trim-both} trims from both |
| 3397 | ends. |
| 3398 | |
| 3399 | @var{char_pred} can be a character, a character set, or a predicate |
| 3400 | procedure to call on each character. If @var{char_pred} is not given |
| 3401 | the default is whitespace as per @code{char-set:whitespace} |
| 3402 | (@pxref{Standard Character Sets}). |
| 3403 | |
| 3404 | @example |
| 3405 | (string-trim " x ") @result{} "x " |
| 3406 | (string-trim-right "banana" #\a) @result{} "banan" |
| 3407 | (string-trim-both ".,xy:;" char-set:punctuation) |
| 3408 | @result{} "xy" |
| 3409 | (string-trim-both "xyzzy" (lambda (c) |
| 3410 | (or (eqv? c #\x) |
| 3411 | (eqv? c #\y)))) |
| 3412 | @result{} "zz" |
| 3413 | @end example |
| 3414 | @end deffn |
| 3415 | |
| 3416 | @node String Modification |
| 3417 | @subsubsection String Modification |
| 3418 | |
| 3419 | These procedures are for modifying strings in-place. This means that the |
| 3420 | result of the operation is not a new string; instead, the original string's |
| 3421 | memory representation is modified. |
| 3422 | |
| 3423 | @rnindex string-set! |
| 3424 | @deffn {Scheme Procedure} string-set! str k chr |
| 3425 | @deffnx {C Function} scm_string_set_x (str, k, chr) |
| 3426 | Store @var{chr} in element @var{k} of @var{str} and return |
| 3427 | an unspecified value. @var{k} must be a valid index of |
| 3428 | @var{str}. |
| 3429 | @end deffn |
| 3430 | |
| 3431 | @deftypefn {C Function} void scm_c_string_set_x (SCM str, size_t k, SCM chr) |
| 3432 | Like @code{scm_string_set_x}, but the index is given as a @code{size_t}. |
| 3433 | @end deftypefn |
| 3434 | |
| 3435 | @rnindex string-fill! |
| 3436 | @deffn {Scheme Procedure} string-fill! str chr [start [end]] |
| 3437 | @deffnx {C Function} scm_substring_fill_x (str, chr, start, end) |
| 3438 | @deffnx {C Function} scm_string_fill_x (str, chr) |
| 3439 | Stores @var{chr} in every element of the given @var{str} and |
| 3440 | returns an unspecified value. |
| 3441 | @end deffn |
| 3442 | |
| 3443 | @deffn {Scheme Procedure} substring-fill! str start end fill |
| 3444 | @deffnx {C Function} scm_substring_fill_x (str, start, end, fill) |
| 3445 | Change every character in @var{str} between @var{start} and |
| 3446 | @var{end} to @var{fill}. |
| 3447 | |
| 3448 | @lisp |
| 3449 | (define y (string-copy "abcdefg")) |
| 3450 | (substring-fill! y 1 3 #\r) |
| 3451 | y |
| 3452 | @result{} "arrdefg" |
| 3453 | @end lisp |
| 3454 | @end deffn |
| 3455 | |
| 3456 | @deffn {Scheme Procedure} substring-move! str1 start1 end1 str2 start2 |
| 3457 | @deffnx {C Function} scm_substring_move_x (str1, start1, end1, str2, start2) |
| 3458 | Copy the substring of @var{str1} bounded by @var{start1} and @var{end1} |
| 3459 | into @var{str2} beginning at position @var{start2}. |
| 3460 | @var{str1} and @var{str2} can be the same string. |
| 3461 | @end deffn |
| 3462 | |
| 3463 | @deffn {Scheme Procedure} string-copy! target tstart s [start [end]] |
| 3464 | @deffnx {C Function} scm_string_copy_x (target, tstart, s, start, end) |
| 3465 | Copy the sequence of characters from index range [@var{start}, |
| 3466 | @var{end}) in string @var{s} to string @var{target}, beginning |
| 3467 | at index @var{tstart}. The characters are copied left-to-right |
| 3468 | or right-to-left as needed -- the copy is guaranteed to work, |
| 3469 | even if @var{target} and @var{s} are the same string. It is an |
| 3470 | error if the copy operation runs off the end of the target |
| 3471 | string. |
| 3472 | @end deffn |
| 3473 | |
| 3474 | |
| 3475 | @node String Comparison |
| 3476 | @subsubsection String Comparison |
| 3477 | |
| 3478 | The procedures in this section are similar to the character ordering |
| 3479 | predicates (@pxref{Characters}), but are defined on character sequences. |
| 3480 | |
| 3481 | The first set is specified in R5RS and has names that end in @code{?}. |
| 3482 | The second set is specified in SRFI-13 and the names have not ending |
| 3483 | @code{?}. |
| 3484 | |
| 3485 | The predicates ending in @code{-ci} ignore the character case |
| 3486 | when comparing strings. For now, case-insensitive comparison is done |
| 3487 | using the R5RS rules, where every lower-case character that has a |
| 3488 | single character upper-case form is converted to uppercase before |
| 3489 | comparison. See @xref{Text Collation, the @code{(ice-9 |
| 3490 | i18n)} module}, for locale-dependent string comparison. |
| 3491 | |
| 3492 | @rnindex string=? |
| 3493 | @deffn {Scheme Procedure} string=? s1 s2 s3 @dots{} |
| 3494 | Lexicographic equality predicate; return @code{#t} if all strings are |
| 3495 | the same length and contain the same characters in the same positions, |
| 3496 | otherwise return @code{#f}. |
| 3497 | |
| 3498 | The procedure @code{string-ci=?} treats upper and lower case |
| 3499 | letters as though they were the same character, but |
| 3500 | @code{string=?} treats upper and lower case as distinct |
| 3501 | characters. |
| 3502 | @end deffn |
| 3503 | |
| 3504 | @rnindex string<? |
| 3505 | @deffn {Scheme Procedure} string<? s1 s2 s3 @dots{} |
| 3506 | Lexicographic ordering predicate; return @code{#t} if, for every pair of |
| 3507 | consecutive string arguments @var{str_i} and @var{str_i+1}, @var{str_i} is |
| 3508 | lexicographically less than @var{str_i+1}. |
| 3509 | @end deffn |
| 3510 | |
| 3511 | @rnindex string<=? |
| 3512 | @deffn {Scheme Procedure} string<=? s1 s2 s3 @dots{} |
| 3513 | Lexicographic ordering predicate; return @code{#t} if, for every pair of |
| 3514 | consecutive string arguments @var{str_i} and @var{str_i+1}, @var{str_i} is |
| 3515 | lexicographically less than or equal to @var{str_i+1}. |
| 3516 | @end deffn |
| 3517 | |
| 3518 | @rnindex string>? |
| 3519 | @deffn {Scheme Procedure} string>? s1 s2 s3 @dots{} |
| 3520 | Lexicographic ordering predicate; return @code{#t} if, for every pair of |
| 3521 | consecutive string arguments @var{str_i} and @var{str_i+1}, @var{str_i} is |
| 3522 | lexicographically greater than @var{str_i+1}. |
| 3523 | @end deffn |
| 3524 | |
| 3525 | @rnindex string>=? |
| 3526 | @deffn {Scheme Procedure} string>=? s1 s2 s3 @dots{} |
| 3527 | Lexicographic ordering predicate; return @code{#t} if, for every pair of |
| 3528 | consecutive string arguments @var{str_i} and @var{str_i+1}, @var{str_i} is |
| 3529 | lexicographically greater than or equal to @var{str_i+1}. |
| 3530 | @end deffn |
| 3531 | |
| 3532 | @rnindex string-ci=? |
| 3533 | @deffn {Scheme Procedure} string-ci=? s1 s2 s3 @dots{} |
| 3534 | Case-insensitive string equality predicate; return @code{#t} if |
| 3535 | all strings are the same length and their component |
| 3536 | characters match (ignoring case) at each position; otherwise |
| 3537 | return @code{#f}. |
| 3538 | @end deffn |
| 3539 | |
| 3540 | @rnindex string-ci<? |
| 3541 | @deffn {Scheme Procedure} string-ci<? s1 s2 s3 @dots{} |
| 3542 | Case insensitive lexicographic ordering predicate; return @code{#t} if, |
| 3543 | for every pair of consecutive string arguments @var{str_i} and |
| 3544 | @var{str_i+1}, @var{str_i} is lexicographically less than @var{str_i+1} |
| 3545 | regardless of case. |
| 3546 | @end deffn |
| 3547 | |
| 3548 | @rnindex string<=? |
| 3549 | @deffn {Scheme Procedure} string-ci<=? s1 s2 s3 @dots{} |
| 3550 | Case insensitive lexicographic ordering predicate; return @code{#t} if, |
| 3551 | for every pair of consecutive string arguments @var{str_i} and |
| 3552 | @var{str_i+1}, @var{str_i} is lexicographically less than or equal to |
| 3553 | @var{str_i+1} regardless of case. |
| 3554 | @end deffn |
| 3555 | |
| 3556 | @rnindex string-ci>? |
| 3557 | @deffn {Scheme Procedure} string-ci>? s1 s2 s3 @dots{} |
| 3558 | Case insensitive lexicographic ordering predicate; return @code{#t} if, |
| 3559 | for every pair of consecutive string arguments @var{str_i} and |
| 3560 | @var{str_i+1}, @var{str_i} is lexicographically greater than |
| 3561 | @var{str_i+1} regardless of case. |
| 3562 | @end deffn |
| 3563 | |
| 3564 | @rnindex string-ci>=? |
| 3565 | @deffn {Scheme Procedure} string-ci>=? s1 s2 s3 @dots{} |
| 3566 | Case insensitive lexicographic ordering predicate; return @code{#t} if, |
| 3567 | for every pair of consecutive string arguments @var{str_i} and |
| 3568 | @var{str_i+1}, @var{str_i} is lexicographically greater than or equal to |
| 3569 | @var{str_i+1} regardless of case. |
| 3570 | @end deffn |
| 3571 | |
| 3572 | @deffn {Scheme Procedure} string-compare s1 s2 proc_lt proc_eq proc_gt [start1 [end1 [start2 [end2]]]] |
| 3573 | @deffnx {C Function} scm_string_compare (s1, s2, proc_lt, proc_eq, proc_gt, start1, end1, start2, end2) |
| 3574 | Apply @var{proc_lt}, @var{proc_eq}, @var{proc_gt} to the |
| 3575 | mismatch index, depending upon whether @var{s1} is less than, |
| 3576 | equal to, or greater than @var{s2}. The mismatch index is the |
| 3577 | largest index @var{i} such that for every 0 <= @var{j} < |
| 3578 | @var{i}, @var{s1}[@var{j}] = @var{s2}[@var{j}] -- that is, |
| 3579 | @var{i} is the first position that does not match. |
| 3580 | @end deffn |
| 3581 | |
| 3582 | @deffn {Scheme Procedure} string-compare-ci s1 s2 proc_lt proc_eq proc_gt [start1 [end1 [start2 [end2]]]] |
| 3583 | @deffnx {C Function} scm_string_compare_ci (s1, s2, proc_lt, proc_eq, proc_gt, start1, end1, start2, end2) |
| 3584 | Apply @var{proc_lt}, @var{proc_eq}, @var{proc_gt} to the |
| 3585 | mismatch index, depending upon whether @var{s1} is less than, |
| 3586 | equal to, or greater than @var{s2}. The mismatch index is the |
| 3587 | largest index @var{i} such that for every 0 <= @var{j} < |
| 3588 | @var{i}, @var{s1}[@var{j}] = @var{s2}[@var{j}] -- that is, |
| 3589 | @var{i} is the first position where the lowercased letters |
| 3590 | do not match. |
| 3591 | |
| 3592 | @end deffn |
| 3593 | |
| 3594 | @deffn {Scheme Procedure} string= s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3595 | @deffnx {C Function} scm_string_eq (s1, s2, start1, end1, start2, end2) |
| 3596 | Return @code{#f} if @var{s1} and @var{s2} are not equal, a true |
| 3597 | value otherwise. |
| 3598 | @end deffn |
| 3599 | |
| 3600 | @deffn {Scheme Procedure} string<> s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3601 | @deffnx {C Function} scm_string_neq (s1, s2, start1, end1, start2, end2) |
| 3602 | Return @code{#f} if @var{s1} and @var{s2} are equal, a true |
| 3603 | value otherwise. |
| 3604 | @end deffn |
| 3605 | |
| 3606 | @deffn {Scheme Procedure} string< s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3607 | @deffnx {C Function} scm_string_lt (s1, s2, start1, end1, start2, end2) |
| 3608 | Return @code{#f} if @var{s1} is greater or equal to @var{s2}, a |
| 3609 | true value otherwise. |
| 3610 | @end deffn |
| 3611 | |
| 3612 | @deffn {Scheme Procedure} string> s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3613 | @deffnx {C Function} scm_string_gt (s1, s2, start1, end1, start2, end2) |
| 3614 | Return @code{#f} if @var{s1} is less or equal to @var{s2}, a |
| 3615 | true value otherwise. |
| 3616 | @end deffn |
| 3617 | |
| 3618 | @deffn {Scheme Procedure} string<= s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3619 | @deffnx {C Function} scm_string_le (s1, s2, start1, end1, start2, end2) |
| 3620 | Return @code{#f} if @var{s1} is greater to @var{s2}, a true |
| 3621 | value otherwise. |
| 3622 | @end deffn |
| 3623 | |
| 3624 | @deffn {Scheme Procedure} string>= s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3625 | @deffnx {C Function} scm_string_ge (s1, s2, start1, end1, start2, end2) |
| 3626 | Return @code{#f} if @var{s1} is less to @var{s2}, a true value |
| 3627 | otherwise. |
| 3628 | @end deffn |
| 3629 | |
| 3630 | @deffn {Scheme Procedure} string-ci= s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3631 | @deffnx {C Function} scm_string_ci_eq (s1, s2, start1, end1, start2, end2) |
| 3632 | Return @code{#f} if @var{s1} and @var{s2} are not equal, a true |
| 3633 | value otherwise. The character comparison is done |
| 3634 | case-insensitively. |
| 3635 | @end deffn |
| 3636 | |
| 3637 | @deffn {Scheme Procedure} string-ci<> s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3638 | @deffnx {C Function} scm_string_ci_neq (s1, s2, start1, end1, start2, end2) |
| 3639 | Return @code{#f} if @var{s1} and @var{s2} are equal, a true |
| 3640 | value otherwise. The character comparison is done |
| 3641 | case-insensitively. |
| 3642 | @end deffn |
| 3643 | |
| 3644 | @deffn {Scheme Procedure} string-ci< s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3645 | @deffnx {C Function} scm_string_ci_lt (s1, s2, start1, end1, start2, end2) |
| 3646 | Return @code{#f} if @var{s1} is greater or equal to @var{s2}, a |
| 3647 | true value otherwise. The character comparison is done |
| 3648 | case-insensitively. |
| 3649 | @end deffn |
| 3650 | |
| 3651 | @deffn {Scheme Procedure} string-ci> s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3652 | @deffnx {C Function} scm_string_ci_gt (s1, s2, start1, end1, start2, end2) |
| 3653 | Return @code{#f} if @var{s1} is less or equal to @var{s2}, a |
| 3654 | true value otherwise. The character comparison is done |
| 3655 | case-insensitively. |
| 3656 | @end deffn |
| 3657 | |
| 3658 | @deffn {Scheme Procedure} string-ci<= s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3659 | @deffnx {C Function} scm_string_ci_le (s1, s2, start1, end1, start2, end2) |
| 3660 | Return @code{#f} if @var{s1} is greater to @var{s2}, a true |
| 3661 | value otherwise. The character comparison is done |
| 3662 | case-insensitively. |
| 3663 | @end deffn |
| 3664 | |
| 3665 | @deffn {Scheme Procedure} string-ci>= s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3666 | @deffnx {C Function} scm_string_ci_ge (s1, s2, start1, end1, start2, end2) |
| 3667 | Return @code{#f} if @var{s1} is less to @var{s2}, a true value |
| 3668 | otherwise. The character comparison is done |
| 3669 | case-insensitively. |
| 3670 | @end deffn |
| 3671 | |
| 3672 | @deffn {Scheme Procedure} string-hash s [bound [start [end]]] |
| 3673 | @deffnx {C Function} scm_substring_hash (s, bound, start, end) |
| 3674 | Compute a hash value for @var{s}. The optional argument @var{bound} is a non-negative exact integer specifying the range of the hash function. A positive value restricts the return value to the range [0,bound). |
| 3675 | @end deffn |
| 3676 | |
| 3677 | @deffn {Scheme Procedure} string-hash-ci s [bound [start [end]]] |
| 3678 | @deffnx {C Function} scm_substring_hash_ci (s, bound, start, end) |
| 3679 | Compute a hash value for @var{s}. The optional argument @var{bound} is a non-negative exact integer specifying the range of the hash function. A positive value restricts the return value to the range [0,bound). |
| 3680 | @end deffn |
| 3681 | |
| 3682 | Because the same visual appearance of an abstract Unicode character can |
| 3683 | be obtained via multiple sequences of Unicode characters, even the |
| 3684 | case-insensitive string comparison functions described above may return |
| 3685 | @code{#f} when presented with strings containing different |
| 3686 | representations of the same character. For example, the Unicode |
| 3687 | character ``LATIN SMALL LETTER S WITH DOT BELOW AND DOT ABOVE'' can be |
| 3688 | represented with a single character (U+1E69) or by the character ``LATIN |
| 3689 | SMALL LETTER S'' (U+0073) followed by the combining marks ``COMBINING |
| 3690 | DOT BELOW'' (U+0323) and ``COMBINING DOT ABOVE'' (U+0307). |
| 3691 | |
| 3692 | For this reason, it is often desirable to ensure that the strings |
| 3693 | to be compared are using a mutually consistent representation for every |
| 3694 | character. The Unicode standard defines two methods of normalizing the |
| 3695 | contents of strings: Decomposition, which breaks composite characters |
| 3696 | into a set of constituent characters with an ordering defined by the |
| 3697 | Unicode Standard; and composition, which performs the converse. |
| 3698 | |
| 3699 | There are two decomposition operations. ``Canonical decomposition'' |
| 3700 | produces character sequences that share the same visual appearance as |
| 3701 | the original characters, while ``compatibility decomposition'' produces |
| 3702 | ones whose visual appearances may differ from the originals but which |
| 3703 | represent the same abstract character. |
| 3704 | |
| 3705 | These operations are encapsulated in the following set of normalization |
| 3706 | forms: |
| 3707 | |
| 3708 | @table @dfn |
| 3709 | @item NFD |
| 3710 | Characters are decomposed to their canonical forms. |
| 3711 | |
| 3712 | @item NFKD |
| 3713 | Characters are decomposed to their compatibility forms. |
| 3714 | |
| 3715 | @item NFC |
| 3716 | Characters are decomposed to their canonical forms, then composed. |
| 3717 | |
| 3718 | @item NFKC |
| 3719 | Characters are decomposed to their compatibility forms, then composed. |
| 3720 | |
| 3721 | @end table |
| 3722 | |
| 3723 | The functions below put their arguments into one of the forms described |
| 3724 | above. |
| 3725 | |
| 3726 | @deffn {Scheme Procedure} string-normalize-nfd s |
| 3727 | @deffnx {C Function} scm_string_normalize_nfd (s) |
| 3728 | Return the @code{NFD} normalized form of @var{s}. |
| 3729 | @end deffn |
| 3730 | |
| 3731 | @deffn {Scheme Procedure} string-normalize-nfkd s |
| 3732 | @deffnx {C Function} scm_string_normalize_nfkd (s) |
| 3733 | Return the @code{NFKD} normalized form of @var{s}. |
| 3734 | @end deffn |
| 3735 | |
| 3736 | @deffn {Scheme Procedure} string-normalize-nfc s |
| 3737 | @deffnx {C Function} scm_string_normalize_nfc (s) |
| 3738 | Return the @code{NFC} normalized form of @var{s}. |
| 3739 | @end deffn |
| 3740 | |
| 3741 | @deffn {Scheme Procedure} string-normalize-nfkc s |
| 3742 | @deffnx {C Function} scm_string_normalize_nfkc (s) |
| 3743 | Return the @code{NFKC} normalized form of @var{s}. |
| 3744 | @end deffn |
| 3745 | |
| 3746 | @node String Searching |
| 3747 | @subsubsection String Searching |
| 3748 | |
| 3749 | @deffn {Scheme Procedure} string-index s char_pred [start [end]] |
| 3750 | @deffnx {C Function} scm_string_index (s, char_pred, start, end) |
| 3751 | Search through the string @var{s} from left to right, returning |
| 3752 | the index of the first occurrence of a character which |
| 3753 | |
| 3754 | @itemize @bullet |
| 3755 | @item |
| 3756 | equals @var{char_pred}, if it is character, |
| 3757 | |
| 3758 | @item |
| 3759 | satisfies the predicate @var{char_pred}, if it is a procedure, |
| 3760 | |
| 3761 | @item |
| 3762 | is in the set @var{char_pred}, if it is a character set. |
| 3763 | @end itemize |
| 3764 | |
| 3765 | Return @code{#f} if no match is found. |
| 3766 | @end deffn |
| 3767 | |
| 3768 | @deffn {Scheme Procedure} string-rindex s char_pred [start [end]] |
| 3769 | @deffnx {C Function} scm_string_rindex (s, char_pred, start, end) |
| 3770 | Search through the string @var{s} from right to left, returning |
| 3771 | the index of the last occurrence of a character which |
| 3772 | |
| 3773 | @itemize @bullet |
| 3774 | @item |
| 3775 | equals @var{char_pred}, if it is character, |
| 3776 | |
| 3777 | @item |
| 3778 | satisfies the predicate @var{char_pred}, if it is a procedure, |
| 3779 | |
| 3780 | @item |
| 3781 | is in the set if @var{char_pred} is a character set. |
| 3782 | @end itemize |
| 3783 | |
| 3784 | Return @code{#f} if no match is found. |
| 3785 | @end deffn |
| 3786 | |
| 3787 | @deffn {Scheme Procedure} string-prefix-length s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3788 | @deffnx {C Function} scm_string_prefix_length (s1, s2, start1, end1, start2, end2) |
| 3789 | Return the length of the longest common prefix of the two |
| 3790 | strings. |
| 3791 | @end deffn |
| 3792 | |
| 3793 | @deffn {Scheme Procedure} string-prefix-length-ci s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3794 | @deffnx {C Function} scm_string_prefix_length_ci (s1, s2, start1, end1, start2, end2) |
| 3795 | Return the length of the longest common prefix of the two |
| 3796 | strings, ignoring character case. |
| 3797 | @end deffn |
| 3798 | |
| 3799 | @deffn {Scheme Procedure} string-suffix-length s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3800 | @deffnx {C Function} scm_string_suffix_length (s1, s2, start1, end1, start2, end2) |
| 3801 | Return the length of the longest common suffix of the two |
| 3802 | strings. |
| 3803 | @end deffn |
| 3804 | |
| 3805 | @deffn {Scheme Procedure} string-suffix-length-ci s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3806 | @deffnx {C Function} scm_string_suffix_length_ci (s1, s2, start1, end1, start2, end2) |
| 3807 | Return the length of the longest common suffix of the two |
| 3808 | strings, ignoring character case. |
| 3809 | @end deffn |
| 3810 | |
| 3811 | @deffn {Scheme Procedure} string-prefix? s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3812 | @deffnx {C Function} scm_string_prefix_p (s1, s2, start1, end1, start2, end2) |
| 3813 | Is @var{s1} a prefix of @var{s2}? |
| 3814 | @end deffn |
| 3815 | |
| 3816 | @deffn {Scheme Procedure} string-prefix-ci? s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3817 | @deffnx {C Function} scm_string_prefix_ci_p (s1, s2, start1, end1, start2, end2) |
| 3818 | Is @var{s1} a prefix of @var{s2}, ignoring character case? |
| 3819 | @end deffn |
| 3820 | |
| 3821 | @deffn {Scheme Procedure} string-suffix? s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3822 | @deffnx {C Function} scm_string_suffix_p (s1, s2, start1, end1, start2, end2) |
| 3823 | Is @var{s1} a suffix of @var{s2}? |
| 3824 | @end deffn |
| 3825 | |
| 3826 | @deffn {Scheme Procedure} string-suffix-ci? s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3827 | @deffnx {C Function} scm_string_suffix_ci_p (s1, s2, start1, end1, start2, end2) |
| 3828 | Is @var{s1} a suffix of @var{s2}, ignoring character case? |
| 3829 | @end deffn |
| 3830 | |
| 3831 | @deffn {Scheme Procedure} string-index-right s char_pred [start [end]] |
| 3832 | @deffnx {C Function} scm_string_index_right (s, char_pred, start, end) |
| 3833 | Search through the string @var{s} from right to left, returning |
| 3834 | the index of the last occurrence of a character which |
| 3835 | |
| 3836 | @itemize @bullet |
| 3837 | @item |
| 3838 | equals @var{char_pred}, if it is character, |
| 3839 | |
| 3840 | @item |
| 3841 | satisfies the predicate @var{char_pred}, if it is a procedure, |
| 3842 | |
| 3843 | @item |
| 3844 | is in the set if @var{char_pred} is a character set. |
| 3845 | @end itemize |
| 3846 | |
| 3847 | Return @code{#f} if no match is found. |
| 3848 | @end deffn |
| 3849 | |
| 3850 | @deffn {Scheme Procedure} string-skip s char_pred [start [end]] |
| 3851 | @deffnx {C Function} scm_string_skip (s, char_pred, start, end) |
| 3852 | Search through the string @var{s} from left to right, returning |
| 3853 | the index of the first occurrence of a character which |
| 3854 | |
| 3855 | @itemize @bullet |
| 3856 | @item |
| 3857 | does not equal @var{char_pred}, if it is character, |
| 3858 | |
| 3859 | @item |
| 3860 | does not satisfy the predicate @var{char_pred}, if it is a |
| 3861 | procedure, |
| 3862 | |
| 3863 | @item |
| 3864 | is not in the set if @var{char_pred} is a character set. |
| 3865 | @end itemize |
| 3866 | @end deffn |
| 3867 | |
| 3868 | @deffn {Scheme Procedure} string-skip-right s char_pred [start [end]] |
| 3869 | @deffnx {C Function} scm_string_skip_right (s, char_pred, start, end) |
| 3870 | Search through the string @var{s} from right to left, returning |
| 3871 | the index of the last occurrence of a character which |
| 3872 | |
| 3873 | @itemize @bullet |
| 3874 | @item |
| 3875 | does not equal @var{char_pred}, if it is character, |
| 3876 | |
| 3877 | @item |
| 3878 | does not satisfy the predicate @var{char_pred}, if it is a |
| 3879 | procedure, |
| 3880 | |
| 3881 | @item |
| 3882 | is not in the set if @var{char_pred} is a character set. |
| 3883 | @end itemize |
| 3884 | @end deffn |
| 3885 | |
| 3886 | @deffn {Scheme Procedure} string-count s char_pred [start [end]] |
| 3887 | @deffnx {C Function} scm_string_count (s, char_pred, start, end) |
| 3888 | Return the count of the number of characters in the string |
| 3889 | @var{s} which |
| 3890 | |
| 3891 | @itemize @bullet |
| 3892 | @item |
| 3893 | equals @var{char_pred}, if it is character, |
| 3894 | |
| 3895 | @item |
| 3896 | satisfies the predicate @var{char_pred}, if it is a procedure. |
| 3897 | |
| 3898 | @item |
| 3899 | is in the set @var{char_pred}, if it is a character set. |
| 3900 | @end itemize |
| 3901 | @end deffn |
| 3902 | |
| 3903 | @deffn {Scheme Procedure} string-contains s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3904 | @deffnx {C Function} scm_string_contains (s1, s2, start1, end1, start2, end2) |
| 3905 | Does string @var{s1} contain string @var{s2}? Return the index |
| 3906 | in @var{s1} where @var{s2} occurs as a substring, or false. |
| 3907 | The optional start/end indices restrict the operation to the |
| 3908 | indicated substrings. |
| 3909 | @end deffn |
| 3910 | |
| 3911 | @deffn {Scheme Procedure} string-contains-ci s1 s2 [start1 [end1 [start2 [end2]]]] |
| 3912 | @deffnx {C Function} scm_string_contains_ci (s1, s2, start1, end1, start2, end2) |
| 3913 | Does string @var{s1} contain string @var{s2}? Return the index |
| 3914 | in @var{s1} where @var{s2} occurs as a substring, or false. |
| 3915 | The optional start/end indices restrict the operation to the |
| 3916 | indicated substrings. Character comparison is done |
| 3917 | case-insensitively. |
| 3918 | @end deffn |
| 3919 | |
| 3920 | @node Alphabetic Case Mapping |
| 3921 | @subsubsection Alphabetic Case Mapping |
| 3922 | |
| 3923 | These are procedures for mapping strings to their upper- or lower-case |
| 3924 | equivalents, respectively, or for capitalizing strings. |
| 3925 | |
| 3926 | They use the basic case mapping rules for Unicode characters. No |
| 3927 | special language or context rules are considered. The resulting strings |
| 3928 | are guaranteed to be the same length as the input strings. |
| 3929 | |
| 3930 | @xref{Character Case Mapping, the @code{(ice-9 |
| 3931 | i18n)} module}, for locale-dependent case conversions. |
| 3932 | |
| 3933 | @deffn {Scheme Procedure} string-upcase str [start [end]] |
| 3934 | @deffnx {C Function} scm_substring_upcase (str, start, end) |
| 3935 | @deffnx {C Function} scm_string_upcase (str) |
| 3936 | Upcase every character in @code{str}. |
| 3937 | @end deffn |
| 3938 | |
| 3939 | @deffn {Scheme Procedure} string-upcase! str [start [end]] |
| 3940 | @deffnx {C Function} scm_substring_upcase_x (str, start, end) |
| 3941 | @deffnx {C Function} scm_string_upcase_x (str) |
| 3942 | Destructively upcase every character in @code{str}. |
| 3943 | |
| 3944 | @lisp |
| 3945 | (string-upcase! y) |
| 3946 | @result{} "ARRDEFG" |
| 3947 | y |
| 3948 | @result{} "ARRDEFG" |
| 3949 | @end lisp |
| 3950 | @end deffn |
| 3951 | |
| 3952 | @deffn {Scheme Procedure} string-downcase str [start [end]] |
| 3953 | @deffnx {C Function} scm_substring_downcase (str, start, end) |
| 3954 | @deffnx {C Function} scm_string_downcase (str) |
| 3955 | Downcase every character in @var{str}. |
| 3956 | @end deffn |
| 3957 | |
| 3958 | @deffn {Scheme Procedure} string-downcase! str [start [end]] |
| 3959 | @deffnx {C Function} scm_substring_downcase_x (str, start, end) |
| 3960 | @deffnx {C Function} scm_string_downcase_x (str) |
| 3961 | Destructively downcase every character in @var{str}. |
| 3962 | |
| 3963 | @lisp |
| 3964 | y |
| 3965 | @result{} "ARRDEFG" |
| 3966 | (string-downcase! y) |
| 3967 | @result{} "arrdefg" |
| 3968 | y |
| 3969 | @result{} "arrdefg" |
| 3970 | @end lisp |
| 3971 | @end deffn |
| 3972 | |
| 3973 | @deffn {Scheme Procedure} string-capitalize str |
| 3974 | @deffnx {C Function} scm_string_capitalize (str) |
| 3975 | Return a freshly allocated string with the characters in |
| 3976 | @var{str}, where the first character of every word is |
| 3977 | capitalized. |
| 3978 | @end deffn |
| 3979 | |
| 3980 | @deffn {Scheme Procedure} string-capitalize! str |
| 3981 | @deffnx {C Function} scm_string_capitalize_x (str) |
| 3982 | Upcase the first character of every word in @var{str} |
| 3983 | destructively and return @var{str}. |
| 3984 | |
| 3985 | @lisp |
| 3986 | y @result{} "hello world" |
| 3987 | (string-capitalize! y) @result{} "Hello World" |
| 3988 | y @result{} "Hello World" |
| 3989 | @end lisp |
| 3990 | @end deffn |
| 3991 | |
| 3992 | @deffn {Scheme Procedure} string-titlecase str [start [end]] |
| 3993 | @deffnx {C Function} scm_string_titlecase (str, start, end) |
| 3994 | Titlecase every first character in a word in @var{str}. |
| 3995 | @end deffn |
| 3996 | |
| 3997 | @deffn {Scheme Procedure} string-titlecase! str [start [end]] |
| 3998 | @deffnx {C Function} scm_string_titlecase_x (str, start, end) |
| 3999 | Destructively titlecase every first character in a word in |
| 4000 | @var{str}. |
| 4001 | @end deffn |
| 4002 | |
| 4003 | @node Reversing and Appending Strings |
| 4004 | @subsubsection Reversing and Appending Strings |
| 4005 | |
| 4006 | @deffn {Scheme Procedure} string-reverse str [start [end]] |
| 4007 | @deffnx {C Function} scm_string_reverse (str, start, end) |
| 4008 | Reverse the string @var{str}. The optional arguments |
| 4009 | @var{start} and @var{end} delimit the region of @var{str} to |
| 4010 | operate on. |
| 4011 | @end deffn |
| 4012 | |
| 4013 | @deffn {Scheme Procedure} string-reverse! str [start [end]] |
| 4014 | @deffnx {C Function} scm_string_reverse_x (str, start, end) |
| 4015 | Reverse the string @var{str} in-place. The optional arguments |
| 4016 | @var{start} and @var{end} delimit the region of @var{str} to |
| 4017 | operate on. The return value is unspecified. |
| 4018 | @end deffn |
| 4019 | |
| 4020 | @rnindex string-append |
| 4021 | @deffn {Scheme Procedure} string-append arg @dots{} |
| 4022 | @deffnx {C Function} scm_string_append (args) |
| 4023 | Return a newly allocated string whose characters form the |
| 4024 | concatenation of the given strings, @var{arg} @enddots{}. |
| 4025 | |
| 4026 | @example |
| 4027 | (let ((h "hello ")) |
| 4028 | (string-append h "world")) |
| 4029 | @result{} "hello world" |
| 4030 | @end example |
| 4031 | @end deffn |
| 4032 | |
| 4033 | @deffn {Scheme Procedure} string-append/shared arg @dots{} |
| 4034 | @deffnx {C Function} scm_string_append_shared (args) |
| 4035 | Like @code{string-append}, but the result may share memory |
| 4036 | with the argument strings. |
| 4037 | @end deffn |
| 4038 | |
| 4039 | @deffn {Scheme Procedure} string-concatenate ls |
| 4040 | @deffnx {C Function} scm_string_concatenate (ls) |
| 4041 | Append the elements (which must be strings) of @var{ls} together into a |
| 4042 | single string. Guaranteed to return a freshly allocated string. |
| 4043 | @end deffn |
| 4044 | |
| 4045 | @deffn {Scheme Procedure} string-concatenate-reverse ls [final_string [end]] |
| 4046 | @deffnx {C Function} scm_string_concatenate_reverse (ls, final_string, end) |
| 4047 | Without optional arguments, this procedure is equivalent to |
| 4048 | |
| 4049 | @lisp |
| 4050 | (string-concatenate (reverse ls)) |
| 4051 | @end lisp |
| 4052 | |
| 4053 | If the optional argument @var{final_string} is specified, it is |
| 4054 | consed onto the beginning to @var{ls} before performing the |
| 4055 | list-reverse and string-concatenate operations. If @var{end} |
| 4056 | is given, only the characters of @var{final_string} up to index |
| 4057 | @var{end} are used. |
| 4058 | |
| 4059 | Guaranteed to return a freshly allocated string. |
| 4060 | @end deffn |
| 4061 | |
| 4062 | @deffn {Scheme Procedure} string-concatenate/shared ls |
| 4063 | @deffnx {C Function} scm_string_concatenate_shared (ls) |
| 4064 | Like @code{string-concatenate}, but the result may share memory |
| 4065 | with the strings in the list @var{ls}. |
| 4066 | @end deffn |
| 4067 | |
| 4068 | @deffn {Scheme Procedure} string-concatenate-reverse/shared ls [final_string [end]] |
| 4069 | @deffnx {C Function} scm_string_concatenate_reverse_shared (ls, final_string, end) |
| 4070 | Like @code{string-concatenate-reverse}, but the result may |
| 4071 | share memory with the strings in the @var{ls} arguments. |
| 4072 | @end deffn |
| 4073 | |
| 4074 | @node Mapping Folding and Unfolding |
| 4075 | @subsubsection Mapping, Folding, and Unfolding |
| 4076 | |
| 4077 | @deffn {Scheme Procedure} string-map proc s [start [end]] |
| 4078 | @deffnx {C Function} scm_string_map (proc, s, start, end) |
| 4079 | @var{proc} is a char->char procedure, it is mapped over |
| 4080 | @var{s}. The order in which the procedure is applied to the |
| 4081 | string elements is not specified. |
| 4082 | @end deffn |
| 4083 | |
| 4084 | @deffn {Scheme Procedure} string-map! proc s [start [end]] |
| 4085 | @deffnx {C Function} scm_string_map_x (proc, s, start, end) |
| 4086 | @var{proc} is a char->char procedure, it is mapped over |
| 4087 | @var{s}. The order in which the procedure is applied to the |
| 4088 | string elements is not specified. The string @var{s} is |
| 4089 | modified in-place, the return value is not specified. |
| 4090 | @end deffn |
| 4091 | |
| 4092 | @deffn {Scheme Procedure} string-for-each proc s [start [end]] |
| 4093 | @deffnx {C Function} scm_string_for_each (proc, s, start, end) |
| 4094 | @var{proc} is mapped over @var{s} in left-to-right order. The |
| 4095 | return value is not specified. |
| 4096 | @end deffn |
| 4097 | |
| 4098 | @deffn {Scheme Procedure} string-for-each-index proc s [start [end]] |
| 4099 | @deffnx {C Function} scm_string_for_each_index (proc, s, start, end) |
| 4100 | Call @code{(@var{proc} i)} for each index i in @var{s}, from left to |
| 4101 | right. |
| 4102 | |
| 4103 | For example, to change characters to alternately upper and lower case, |
| 4104 | |
| 4105 | @example |
| 4106 | (define str (string-copy "studly")) |
| 4107 | (string-for-each-index |
| 4108 | (lambda (i) |
| 4109 | (string-set! str i |
| 4110 | ((if (even? i) char-upcase char-downcase) |
| 4111 | (string-ref str i)))) |
| 4112 | str) |
| 4113 | str @result{} "StUdLy" |
| 4114 | @end example |
| 4115 | @end deffn |
| 4116 | |
| 4117 | @deffn {Scheme Procedure} string-fold kons knil s [start [end]] |
| 4118 | @deffnx {C Function} scm_string_fold (kons, knil, s, start, end) |
| 4119 | Fold @var{kons} over the characters of @var{s}, with @var{knil} |
| 4120 | as the terminating element, from left to right. @var{kons} |
| 4121 | must expect two arguments: The actual character and the last |
| 4122 | result of @var{kons}' application. |
| 4123 | @end deffn |
| 4124 | |
| 4125 | @deffn {Scheme Procedure} string-fold-right kons knil s [start [end]] |
| 4126 | @deffnx {C Function} scm_string_fold_right (kons, knil, s, start, end) |
| 4127 | Fold @var{kons} over the characters of @var{s}, with @var{knil} |
| 4128 | as the terminating element, from right to left. @var{kons} |
| 4129 | must expect two arguments: The actual character and the last |
| 4130 | result of @var{kons}' application. |
| 4131 | @end deffn |
| 4132 | |
| 4133 | @deffn {Scheme Procedure} string-unfold p f g seed [base [make_final]] |
| 4134 | @deffnx {C Function} scm_string_unfold (p, f, g, seed, base, make_final) |
| 4135 | @itemize @bullet |
| 4136 | @item @var{g} is used to generate a series of @emph{seed} |
| 4137 | values from the initial @var{seed}: @var{seed}, (@var{g} |
| 4138 | @var{seed}), (@var{g}^2 @var{seed}), (@var{g}^3 @var{seed}), |
| 4139 | @dots{} |
| 4140 | @item @var{p} tells us when to stop -- when it returns true |
| 4141 | when applied to one of these seed values. |
| 4142 | @item @var{f} maps each seed value to the corresponding |
| 4143 | character in the result string. These chars are assembled |
| 4144 | into the string in a left-to-right order. |
| 4145 | @item @var{base} is the optional initial/leftmost portion |
| 4146 | of the constructed string; it default to the empty |
| 4147 | string. |
| 4148 | @item @var{make_final} is applied to the terminal seed |
| 4149 | value (on which @var{p} returns true) to produce |
| 4150 | the final/rightmost portion of the constructed string. |
| 4151 | The default is nothing extra. |
| 4152 | @end itemize |
| 4153 | @end deffn |
| 4154 | |
| 4155 | @deffn {Scheme Procedure} string-unfold-right p f g seed [base [make_final]] |
| 4156 | @deffnx {C Function} scm_string_unfold_right (p, f, g, seed, base, make_final) |
| 4157 | @itemize @bullet |
| 4158 | @item @var{g} is used to generate a series of @emph{seed} |
| 4159 | values from the initial @var{seed}: @var{seed}, (@var{g} |
| 4160 | @var{seed}), (@var{g}^2 @var{seed}), (@var{g}^3 @var{seed}), |
| 4161 | @dots{} |
| 4162 | @item @var{p} tells us when to stop -- when it returns true |
| 4163 | when applied to one of these seed values. |
| 4164 | @item @var{f} maps each seed value to the corresponding |
| 4165 | character in the result string. These chars are assembled |
| 4166 | into the string in a right-to-left order. |
| 4167 | @item @var{base} is the optional initial/rightmost portion |
| 4168 | of the constructed string; it default to the empty |
| 4169 | string. |
| 4170 | @item @var{make_final} is applied to the terminal seed |
| 4171 | value (on which @var{p} returns true) to produce |
| 4172 | the final/leftmost portion of the constructed string. |
| 4173 | It defaults to @code{(lambda (x) )}. |
| 4174 | @end itemize |
| 4175 | @end deffn |
| 4176 | |
| 4177 | @node Miscellaneous String Operations |
| 4178 | @subsubsection Miscellaneous String Operations |
| 4179 | |
| 4180 | @deffn {Scheme Procedure} xsubstring s from [to [start [end]]] |
| 4181 | @deffnx {C Function} scm_xsubstring (s, from, to, start, end) |
| 4182 | This is the @emph{extended substring} procedure that implements |
| 4183 | replicated copying of a substring of some string. |
| 4184 | |
| 4185 | @var{s} is a string, @var{start} and @var{end} are optional |
| 4186 | arguments that demarcate a substring of @var{s}, defaulting to |
| 4187 | 0 and the length of @var{s}. Replicate this substring up and |
| 4188 | down index space, in both the positive and negative directions. |
| 4189 | @code{xsubstring} returns the substring of this string |
| 4190 | beginning at index @var{from}, and ending at @var{to}, which |
| 4191 | defaults to @var{from} + (@var{end} - @var{start}). |
| 4192 | @end deffn |
| 4193 | |
| 4194 | @deffn {Scheme Procedure} string-xcopy! target tstart s sfrom [sto [start [end]]] |
| 4195 | @deffnx {C Function} scm_string_xcopy_x (target, tstart, s, sfrom, sto, start, end) |
| 4196 | Exactly the same as @code{xsubstring}, but the extracted text |
| 4197 | is written into the string @var{target} starting at index |
| 4198 | @var{tstart}. The operation is not defined if @code{(eq? |
| 4199 | @var{target} @var{s})} or these arguments share storage -- you |
| 4200 | cannot copy a string on top of itself. |
| 4201 | @end deffn |
| 4202 | |
| 4203 | @deffn {Scheme Procedure} string-replace s1 s2 [start1 [end1 [start2 [end2]]]] |
| 4204 | @deffnx {C Function} scm_string_replace (s1, s2, start1, end1, start2, end2) |
| 4205 | Return the string @var{s1}, but with the characters |
| 4206 | @var{start1} @dots{} @var{end1} replaced by the characters |
| 4207 | @var{start2} @dots{} @var{end2} from @var{s2}. |
| 4208 | @end deffn |
| 4209 | |
| 4210 | @deffn {Scheme Procedure} string-tokenize s [token_set [start [end]]] |
| 4211 | @deffnx {C Function} scm_string_tokenize (s, token_set, start, end) |
| 4212 | Split the string @var{s} into a list of substrings, where each |
| 4213 | substring is a maximal non-empty contiguous sequence of |
| 4214 | characters from the character set @var{token_set}, which |
| 4215 | defaults to @code{char-set:graphic}. |
| 4216 | If @var{start} or @var{end} indices are provided, they restrict |
| 4217 | @code{string-tokenize} to operating on the indicated substring |
| 4218 | of @var{s}. |
| 4219 | @end deffn |
| 4220 | |
| 4221 | @deffn {Scheme Procedure} string-filter char_pred s [start [end]] |
| 4222 | @deffnx {C Function} scm_string_filter (char_pred, s, start, end) |
| 4223 | Filter the string @var{s}, retaining only those characters which |
| 4224 | satisfy @var{char_pred}. |
| 4225 | |
| 4226 | If @var{char_pred} is a procedure, it is applied to each character as |
| 4227 | a predicate, if it is a character, it is tested for equality and if it |
| 4228 | is a character set, it is tested for membership. |
| 4229 | @end deffn |
| 4230 | |
| 4231 | @deffn {Scheme Procedure} string-delete char_pred s [start [end]] |
| 4232 | @deffnx {C Function} scm_string_delete (char_pred, s, start, end) |
| 4233 | Delete characters satisfying @var{char_pred} from @var{s}. |
| 4234 | |
| 4235 | If @var{char_pred} is a procedure, it is applied to each character as |
| 4236 | a predicate, if it is a character, it is tested for equality and if it |
| 4237 | is a character set, it is tested for membership. |
| 4238 | @end deffn |
| 4239 | |
| 4240 | @node Representing Strings as Bytes |
| 4241 | @subsubsection Representing Strings as Bytes |
| 4242 | |
| 4243 | Out in the cold world outside of Guile, not all strings are treated in |
| 4244 | the same way. Out there there are only bytes, and there are many ways |
| 4245 | of representing a strings (sequences of characters) as binary data |
| 4246 | (sequences of bytes). |
| 4247 | |
| 4248 | As a user, usually you don't have to think about this very much. When |
| 4249 | you type on your keyboard, your system encodes your keystrokes as bytes |
| 4250 | according to the locale that you have configured on your computer. |
| 4251 | Guile uses the locale to decode those bytes back into characters -- |
| 4252 | hopefully the same characters that you typed in. |
| 4253 | |
| 4254 | All is not so clear when dealing with a system with multiple users, such |
| 4255 | as a web server. Your web server might get a request from one user for |
| 4256 | data encoded in the ISO-8859-1 character set, and then another request |
| 4257 | from a different user for UTF-8 data. |
| 4258 | |
| 4259 | @cindex iconv |
| 4260 | @cindex character encoding |
| 4261 | Guile provides an @dfn{iconv} module for converting between strings and |
| 4262 | sequences of bytes. @xref{Bytevectors}, for more on how Guile |
| 4263 | represents raw byte sequences. This module gets its name from the |
| 4264 | common @sc{unix} command of the same name. |
| 4265 | |
| 4266 | Note that often it is sufficient to just read and write strings from |
| 4267 | ports instead of using these functions. To do this, specify the port |
| 4268 | encoding using @code{set-port-encoding!}. @xref{Ports}, for more on |
| 4269 | ports and character encodings. |
| 4270 | |
| 4271 | Unlike the rest of the procedures in this section, you have to load the |
| 4272 | @code{iconv} module before having access to these procedures: |
| 4273 | |
| 4274 | @example |
| 4275 | (use-modules (ice-9 iconv)) |
| 4276 | @end example |
| 4277 | |
| 4278 | @deffn {Scheme Procedure} string->bytevector string encoding [conversion-strategy] |
| 4279 | Encode @var{string} as a sequence of bytes. |
| 4280 | |
| 4281 | The string will be encoded in the character set specified by the |
| 4282 | @var{encoding} string. If the string has characters that cannot be |
| 4283 | represented in the encoding, by default this procedure raises an |
| 4284 | @code{encoding-error}. Pass a @var{conversion-strategy} argument to |
| 4285 | specify other behaviors. |
| 4286 | |
| 4287 | The return value is a bytevector. @xref{Bytevectors}, for more on |
| 4288 | bytevectors. @xref{Ports}, for more on character encodings and |
| 4289 | conversion strategies. |
| 4290 | @end deffn |
| 4291 | |
| 4292 | @deffn {Scheme Procedure} bytevector->string bytevector encoding [conversion-strategy] |
| 4293 | Decode @var{bytevector} into a string. |
| 4294 | |
| 4295 | The bytes will be decoded from the character set by the @var{encoding} |
| 4296 | string. If the bytes do not form a valid encoding, by default this |
| 4297 | procedure raises an @code{decoding-error}. As with |
| 4298 | @code{string->bytevector}, pass the optional @var{conversion-strategy} |
| 4299 | argument to modify this behavior. @xref{Ports}, for more on character |
| 4300 | encodings and conversion strategies. |
| 4301 | @end deffn |
| 4302 | |
| 4303 | @deffn {Scheme Procedure} call-with-output-encoded-string encoding proc [conversion-strategy] |
| 4304 | Like @code{call-with-output-string}, but instead of returning a string, |
| 4305 | returns a encoding of the string according to @var{encoding}, as a |
| 4306 | bytevector. This procedure can be more efficient than collecting a |
| 4307 | string and then converting it via @code{string->bytevector}. |
| 4308 | @end deffn |
| 4309 | |
| 4310 | @node Conversion to/from C |
| 4311 | @subsubsection Conversion to/from C |
| 4312 | |
| 4313 | When creating a Scheme string from a C string or when converting a |
| 4314 | Scheme string to a C string, the concept of character encoding becomes |
| 4315 | important. |
| 4316 | |
| 4317 | In C, a string is just a sequence of bytes, and the character encoding |
| 4318 | describes the relation between these bytes and the actual characters |
| 4319 | that make up the string. For Scheme strings, character encoding is not |
| 4320 | an issue (most of the time), since in Scheme you usually treat strings |
| 4321 | as character sequences, not byte sequences. |
| 4322 | |
| 4323 | Converting to C and converting from C each have their own challenges. |
| 4324 | |
| 4325 | When converting from C to Scheme, it is important that the sequence of |
| 4326 | bytes in the C string be valid with respect to its encoding. ASCII |
| 4327 | strings, for example, can't have any bytes greater than 127. An ASCII |
| 4328 | byte greater than 127 is considered @emph{ill-formed} and cannot be |
| 4329 | converted into a Scheme character. |
| 4330 | |
| 4331 | Problems can occur in the reverse operation as well. Not all character |
| 4332 | encodings can hold all possible Scheme characters. Some encodings, like |
| 4333 | ASCII for example, can only describe a small subset of all possible |
| 4334 | characters. So, when converting to C, one must first decide what to do |
| 4335 | with Scheme characters that can't be represented in the C string. |
| 4336 | |
| 4337 | Converting a Scheme string to a C string will often allocate fresh |
| 4338 | memory to hold the result. You must take care that this memory is |
| 4339 | properly freed eventually. In many cases, this can be achieved by |
| 4340 | using @code{scm_dynwind_free} inside an appropriate dynwind context, |
| 4341 | @xref{Dynamic Wind}. |
| 4342 | |
| 4343 | @deftypefn {C Function} SCM scm_from_locale_string (const char *str) |
| 4344 | @deftypefnx {C Function} SCM scm_from_locale_stringn (const char *str, size_t len) |
| 4345 | Creates a new Scheme string that has the same contents as @var{str} when |
| 4346 | interpreted in the character encoding of the current locale. |
| 4347 | |
| 4348 | For @code{scm_from_locale_string}, @var{str} must be null-terminated. |
| 4349 | |
| 4350 | For @code{scm_from_locale_stringn}, @var{len} specifies the length of |
| 4351 | @var{str} in bytes, and @var{str} does not need to be null-terminated. |
| 4352 | If @var{len} is @code{(size_t)-1}, then @var{str} does need to be |
| 4353 | null-terminated and the real length will be found with @code{strlen}. |
| 4354 | |
| 4355 | If the C string is ill-formed, an error will be raised. |
| 4356 | |
| 4357 | Note that these functions should @emph{not} be used to convert C string |
| 4358 | constants, because there is no guarantee that the current locale will |
| 4359 | match that of the execution character set, used for string and character |
| 4360 | constants. Most modern C compilers use UTF-8 by default, so to convert |
| 4361 | C string constants we recommend @code{scm_from_utf8_string}. |
| 4362 | @end deftypefn |
| 4363 | |
| 4364 | @deftypefn {C Function} SCM scm_take_locale_string (char *str) |
| 4365 | @deftypefnx {C Function} SCM scm_take_locale_stringn (char *str, size_t len) |
| 4366 | Like @code{scm_from_locale_string} and @code{scm_from_locale_stringn}, |
| 4367 | respectively, but also frees @var{str} with @code{free} eventually. |
| 4368 | Thus, you can use this function when you would free @var{str} anyway |
| 4369 | immediately after creating the Scheme string. In certain cases, Guile |
| 4370 | can then use @var{str} directly as its internal representation. |
| 4371 | @end deftypefn |
| 4372 | |
| 4373 | @deftypefn {C Function} {char *} scm_to_locale_string (SCM str) |
| 4374 | @deftypefnx {C Function} {char *} scm_to_locale_stringn (SCM str, size_t *lenp) |
| 4375 | Returns a C string with the same contents as @var{str} in the character |
| 4376 | encoding of the current locale. The C string must be freed with |
| 4377 | @code{free} eventually, maybe by using @code{scm_dynwind_free}, |
| 4378 | @xref{Dynamic Wind}. |
| 4379 | |
| 4380 | For @code{scm_to_locale_string}, the returned string is |
| 4381 | null-terminated and an error is signalled when @var{str} contains |
| 4382 | @code{#\nul} characters. |
| 4383 | |
| 4384 | For @code{scm_to_locale_stringn} and @var{lenp} not @code{NULL}, |
| 4385 | @var{str} might contain @code{#\nul} characters and the length of the |
| 4386 | returned string in bytes is stored in @code{*@var{lenp}}. The |
| 4387 | returned string will not be null-terminated in this case. If |
| 4388 | @var{lenp} is @code{NULL}, @code{scm_to_locale_stringn} behaves like |
| 4389 | @code{scm_to_locale_string}. |
| 4390 | |
| 4391 | If a character in @var{str} cannot be represented in the character |
| 4392 | encoding of the current locale, the default port conversion strategy is |
| 4393 | used. @xref{Ports}, for more on conversion strategies. |
| 4394 | |
| 4395 | If the conversion strategy is @code{error}, an error will be raised. If |
| 4396 | it is @code{substitute}, a replacement character, such as a question |
| 4397 | mark, will be inserted in its place. If it is @code{escape}, a hex |
| 4398 | escape will be inserted in its place. |
| 4399 | @end deftypefn |
| 4400 | |
| 4401 | @deftypefn {C Function} size_t scm_to_locale_stringbuf (SCM str, char *buf, size_t max_len) |
| 4402 | Puts @var{str} as a C string in the current locale encoding into the |
| 4403 | memory pointed to by @var{buf}. The buffer at @var{buf} has room for |
| 4404 | @var{max_len} bytes and @code{scm_to_local_stringbuf} will never store |
| 4405 | more than that. No terminating @code{'\0'} will be stored. |
| 4406 | |
| 4407 | The return value of @code{scm_to_locale_stringbuf} is the number of |
| 4408 | bytes that are needed for all of @var{str}, regardless of whether |
| 4409 | @var{buf} was large enough to hold them. Thus, when the return value |
| 4410 | is larger than @var{max_len}, only @var{max_len} bytes have been |
| 4411 | stored and you probably need to try again with a larger buffer. |
| 4412 | @end deftypefn |
| 4413 | |
| 4414 | For most situations, string conversion should occur using the current |
| 4415 | locale, such as with the functions above. But there may be cases where |
| 4416 | one wants to convert strings from a character encoding other than the |
| 4417 | locale's character encoding. For these cases, the lower-level functions |
| 4418 | @code{scm_to_stringn} and @code{scm_from_stringn} are provided. These |
| 4419 | functions should seldom be necessary if one is properly using locales. |
| 4420 | |
| 4421 | @deftp {C Type} scm_t_string_failed_conversion_handler |
| 4422 | This is an enumerated type that can take one of three values: |
| 4423 | @code{SCM_FAILED_CONVERSION_ERROR}, |
| 4424 | @code{SCM_FAILED_CONVERSION_QUESTION_MARK}, and |
| 4425 | @code{SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE}. They are used to indicate |
| 4426 | a strategy for handling characters that cannot be converted to or from a |
| 4427 | given character encoding. @code{SCM_FAILED_CONVERSION_ERROR} indicates |
| 4428 | that a conversion should throw an error if some characters cannot be |
| 4429 | converted. @code{SCM_FAILED_CONVERSION_QUESTION_MARK} indicates that a |
| 4430 | conversion should replace unconvertable characters with the question |
| 4431 | mark character. And, @code{SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE} |
| 4432 | requests that a conversion should replace an unconvertable character |
| 4433 | with an escape sequence. |
| 4434 | |
| 4435 | While all three strategies apply when converting Scheme strings to C, |
| 4436 | only @code{SCM_FAILED_CONVERSION_ERROR} and |
| 4437 | @code{SCM_FAILED_CONVERSION_QUESTION_MARK} can be used when converting C |
| 4438 | strings to Scheme. |
| 4439 | @end deftp |
| 4440 | |
| 4441 | @deftypefn {C Function} char *scm_to_stringn (SCM str, size_t *lenp, const char *encoding, scm_t_string_failed_conversion_handler handler) |
| 4442 | This function returns a newly allocated C string from the Guile string |
| 4443 | @var{str}. The length of the returned string in bytes will be returned in |
| 4444 | @var{lenp}. The character encoding of the C string is passed as the ASCII, |
| 4445 | null-terminated C string @var{encoding}. The @var{handler} parameter |
| 4446 | gives a strategy for dealing with characters that cannot be converted |
| 4447 | into @var{encoding}. |
| 4448 | |
| 4449 | If @var{lenp} is @code{NULL}, this function will return a null-terminated C |
| 4450 | string. It will throw an error if the string contains a null |
| 4451 | character. |
| 4452 | |
| 4453 | The Scheme interface to this function is @code{string->bytevector}, from the |
| 4454 | @code{ice-9 iconv} module. @xref{Representing Strings as Bytes}. |
| 4455 | @end deftypefn |
| 4456 | |
| 4457 | @deftypefn {C Function} SCM scm_from_stringn (const char *str, size_t len, const char *encoding, scm_t_string_failed_conversion_handler handler) |
| 4458 | This function returns a scheme string from the C string @var{str}. The |
| 4459 | length in bytes of the C string is input as @var{len}. The encoding of the C |
| 4460 | string is passed as the ASCII, null-terminated C string @code{encoding}. |
| 4461 | The @var{handler} parameters suggests a strategy for dealing with |
| 4462 | unconvertable characters. |
| 4463 | |
| 4464 | The Scheme interface to this function is @code{bytevector->string}. |
| 4465 | @xref{Representing Strings as Bytes}. |
| 4466 | @end deftypefn |
| 4467 | |
| 4468 | The following conversion functions are provided as a convenience for the |
| 4469 | most commonly used encodings. |
| 4470 | |
| 4471 | @deftypefn {C Function} SCM scm_from_latin1_string (const char *str) |
| 4472 | @deftypefnx {C Function} SCM scm_from_utf8_string (const char *str) |
| 4473 | @deftypefnx {C Function} SCM scm_from_utf32_string (const scm_t_wchar *str) |
| 4474 | Return a scheme string from the null-terminated C string @var{str}, |
| 4475 | which is ISO-8859-1-, UTF-8-, or UTF-32-encoded. These functions should |
| 4476 | be used to convert hard-coded C string constants into Scheme strings. |
| 4477 | @end deftypefn |
| 4478 | |
| 4479 | @deftypefn {C Function} SCM scm_from_latin1_stringn (const char *str, size_t len) |
| 4480 | @deftypefnx {C Function} SCM scm_from_utf8_stringn (const char *str, size_t len) |
| 4481 | @deftypefnx {C Function} SCM scm_from_utf32_stringn (const scm_t_wchar *str, size_t len) |
| 4482 | Return a scheme string from C string @var{str}, which is ISO-8859-1-, |
| 4483 | UTF-8-, or UTF-32-encoded, of length @var{len}. @var{len} is the number |
| 4484 | of bytes pointed to by @var{str} for @code{scm_from_latin1_stringn} and |
| 4485 | @code{scm_from_utf8_stringn}; it is the number of elements (code points) |
| 4486 | in @var{str} in the case of @code{scm_from_utf32_stringn}. |
| 4487 | @end deftypefn |
| 4488 | |
| 4489 | @deftypefn {C function} char *scm_to_latin1_stringn (SCM str, size_t *lenp) |
| 4490 | @deftypefnx {C function} char *scm_to_utf8_stringn (SCM str, size_t *lenp) |
| 4491 | @deftypefnx {C function} scm_t_wchar *scm_to_utf32_stringn (SCM str, size_t *lenp) |
| 4492 | Return a newly allocated, ISO-8859-1-, UTF-8-, or UTF-32-encoded C string |
| 4493 | from Scheme string @var{str}. An error is thrown when @var{str} |
| 4494 | cannot be converted to the specified encoding. If @var{lenp} is |
| 4495 | @code{NULL}, the returned C string will be null terminated, and an error |
| 4496 | will be thrown if the C string would otherwise contain null |
| 4497 | characters. If @var{lenp} is not @code{NULL}, the string is not null terminated, |
| 4498 | and the length of the returned string is returned in @var{lenp}. The length |
| 4499 | returned is the number of bytes for @code{scm_to_latin1_stringn} and |
| 4500 | @code{scm_to_utf8_stringn}; it is the number of elements (code points) |
| 4501 | for @code{scm_to_utf32_stringn}. |
| 4502 | @end deftypefn |
| 4503 | |
| 4504 | It is not often the case, but sometimes when you are dealing with the |
| 4505 | implementation details of a port, you need to encode and decode strings |
| 4506 | according to the encoding and conversion strategy of the port. There |
| 4507 | are some convenience functions for that purpose as well. |
| 4508 | |
| 4509 | @deftypefn {C Function} SCM scm_from_port_string (const char *str, SCM port) |
| 4510 | @deftypefnx {C Function} SCM scm_from_port_stringn (const char *str, size_t len, SCM port) |
| 4511 | @deftypefnx {C Function} char* scm_to_port_string (SCM str, SCM port) |
| 4512 | @deftypefnx {C Function} char* scm_to_port_stringn (SCM str, size_t *lenp, SCM port) |
| 4513 | Like @code{scm_from_stringn} and friends, except they take their |
| 4514 | encoding and conversion strategy from a given port object. |
| 4515 | @end deftypefn |
| 4516 | |
| 4517 | @node String Internals |
| 4518 | @subsubsection String Internals |
| 4519 | |
| 4520 | Guile stores each string in memory as a contiguous array of Unicode code |
| 4521 | points along with an associated set of attributes. If all of the code |
| 4522 | points of a string have an integer range between 0 and 255 inclusive, |
| 4523 | the code point array is stored as one byte per code point: it is stored |
| 4524 | as an ISO-8859-1 (aka Latin-1) string. If any of the code points of the |
| 4525 | string has an integer value greater that 255, the code point array is |
| 4526 | stored as four bytes per code point: it is stored as a UTF-32 string. |
| 4527 | |
| 4528 | Conversion between the one-byte-per-code-point and |
| 4529 | four-bytes-per-code-point representations happens automatically as |
| 4530 | necessary. |
| 4531 | |
| 4532 | No API is provided to set the internal representation of strings; |
| 4533 | however, there are pair of procedures available to query it. These are |
| 4534 | debugging procedures. Using them in production code is discouraged, |
| 4535 | since the details of Guile's internal representation of strings may |
| 4536 | change from release to release. |
| 4537 | |
| 4538 | @deffn {Scheme Procedure} string-bytes-per-char str |
| 4539 | @deffnx {C Function} scm_string_bytes_per_char (str) |
| 4540 | Return the number of bytes used to encode a Unicode code point in string |
| 4541 | @var{str}. The result is one or four. |
| 4542 | @end deffn |
| 4543 | |
| 4544 | @deffn {Scheme Procedure} %string-dump str |
| 4545 | @deffnx {C Function} scm_sys_string_dump (str) |
| 4546 | Returns an association list containing debugging information for |
| 4547 | @var{str}. The association list has the following entries. |
| 4548 | @table @code |
| 4549 | |
| 4550 | @item string |
| 4551 | The string itself. |
| 4552 | |
| 4553 | @item start |
| 4554 | The start index of the string into its stringbuf |
| 4555 | |
| 4556 | @item length |
| 4557 | The length of the string |
| 4558 | |
| 4559 | @item shared |
| 4560 | If this string is a substring, it returns its |
| 4561 | parent string. Otherwise, it returns @code{#f} |
| 4562 | |
| 4563 | @item read-only |
| 4564 | @code{#t} if the string is read-only |
| 4565 | |
| 4566 | @item stringbuf-chars |
| 4567 | A new string containing this string's stringbuf's characters |
| 4568 | |
| 4569 | @item stringbuf-length |
| 4570 | The number of characters in this stringbuf |
| 4571 | |
| 4572 | @item stringbuf-shared |
| 4573 | @code{#t} if this stringbuf is shared |
| 4574 | |
| 4575 | @item stringbuf-wide |
| 4576 | @code{#t} if this stringbuf's characters are stored in a 32-bit buffer, |
| 4577 | or @code{#f} if they are stored in an 8-bit buffer |
| 4578 | @end table |
| 4579 | @end deffn |
| 4580 | |
| 4581 | |
| 4582 | @node Bytevectors |
| 4583 | @subsection Bytevectors |
| 4584 | |
| 4585 | @cindex bytevector |
| 4586 | @cindex R6RS |
| 4587 | |
| 4588 | A @dfn{bytevector} is a raw bit string. The @code{(rnrs bytevectors)} |
| 4589 | module provides the programming interface specified by the |
| 4590 | @uref{http://www.r6rs.org/, Revised^6 Report on the Algorithmic Language |
| 4591 | Scheme (R6RS)}. It contains procedures to manipulate bytevectors and |
| 4592 | interpret their contents in a number of ways: bytevector contents can be |
| 4593 | accessed as signed or unsigned integer of various sizes and endianness, |
| 4594 | as IEEE-754 floating point numbers, or as strings. It is a useful tool |
| 4595 | to encode and decode binary data. |
| 4596 | |
| 4597 | The R6RS (Section 4.3.4) specifies an external representation for |
| 4598 | bytevectors, whereby the octets (integers in the range 0--255) contained |
| 4599 | in the bytevector are represented as a list prefixed by @code{#vu8}: |
| 4600 | |
| 4601 | @lisp |
| 4602 | #vu8(1 53 204) |
| 4603 | @end lisp |
| 4604 | |
| 4605 | denotes a 3-byte bytevector containing the octets 1, 53, and 204. Like |
| 4606 | string literals, booleans, etc., bytevectors are ``self-quoting'', i.e., |
| 4607 | they do not need to be quoted: |
| 4608 | |
| 4609 | @lisp |
| 4610 | #vu8(1 53 204) |
| 4611 | @result{} #vu8(1 53 204) |
| 4612 | @end lisp |
| 4613 | |
| 4614 | Bytevectors can be used with the binary input/output primitives of the |
| 4615 | R6RS (@pxref{R6RS I/O Ports}). |
| 4616 | |
| 4617 | @menu |
| 4618 | * Bytevector Endianness:: Dealing with byte order. |
| 4619 | * Bytevector Manipulation:: Creating, copying, manipulating bytevectors. |
| 4620 | * Bytevectors as Integers:: Interpreting bytes as integers. |
| 4621 | * Bytevectors and Integer Lists:: Converting to/from an integer list. |
| 4622 | * Bytevectors as Floats:: Interpreting bytes as real numbers. |
| 4623 | * Bytevectors as Strings:: Interpreting bytes as Unicode strings. |
| 4624 | * Bytevectors as Arrays:: Guile extension to the bytevector API. |
| 4625 | * Bytevectors as Uniform Vectors:: Bytevectors and SRFI-4. |
| 4626 | @end menu |
| 4627 | |
| 4628 | @node Bytevector Endianness |
| 4629 | @subsubsection Endianness |
| 4630 | |
| 4631 | @cindex endianness |
| 4632 | @cindex byte order |
| 4633 | @cindex word order |
| 4634 | |
| 4635 | Some of the following procedures take an @var{endianness} parameter. |
| 4636 | The @dfn{endianness} is defined as the order of bytes in multi-byte |
| 4637 | numbers: numbers encoded in @dfn{big endian} have their most |
| 4638 | significant bytes written first, whereas numbers encoded in |
| 4639 | @dfn{little endian} have their least significant bytes |
| 4640 | first@footnote{Big-endian and little-endian are the most common |
| 4641 | ``endiannesses'', but others do exist. For instance, the GNU MP |
| 4642 | library allows @dfn{word order} to be specified independently of |
| 4643 | @dfn{byte order} (@pxref{Integer Import and Export,,, gmp, The GNU |
| 4644 | Multiple Precision Arithmetic Library Manual}).}. |
| 4645 | |
| 4646 | Little-endian is the native endianness of the IA32 architecture and |
| 4647 | its derivatives, while big-endian is native to SPARC and PowerPC, |
| 4648 | among others. The @code{native-endianness} procedure returns the |
| 4649 | native endianness of the machine it runs on. |
| 4650 | |
| 4651 | @deffn {Scheme Procedure} native-endianness |
| 4652 | @deffnx {C Function} scm_native_endianness () |
| 4653 | Return a value denoting the native endianness of the host machine. |
| 4654 | @end deffn |
| 4655 | |
| 4656 | @deffn {Scheme Macro} endianness symbol |
| 4657 | Return an object denoting the endianness specified by @var{symbol}. If |
| 4658 | @var{symbol} is neither @code{big} nor @code{little} then an error is |
| 4659 | raised at expand-time. |
| 4660 | @end deffn |
| 4661 | |
| 4662 | @defvr {C Variable} scm_endianness_big |
| 4663 | @defvrx {C Variable} scm_endianness_little |
| 4664 | The objects denoting big- and little-endianness, respectively. |
| 4665 | @end defvr |
| 4666 | |
| 4667 | |
| 4668 | @node Bytevector Manipulation |
| 4669 | @subsubsection Manipulating Bytevectors |
| 4670 | |
| 4671 | Bytevectors can be created, copied, and analyzed with the following |
| 4672 | procedures and C functions. |
| 4673 | |
| 4674 | @deffn {Scheme Procedure} make-bytevector len [fill] |
| 4675 | @deffnx {C Function} scm_make_bytevector (len, fill) |
| 4676 | @deffnx {C Function} scm_c_make_bytevector (size_t len) |
| 4677 | Return a new bytevector of @var{len} bytes. Optionally, if @var{fill} |
| 4678 | is given, fill it with @var{fill}; @var{fill} must be in the range |
| 4679 | [-128,255]. |
| 4680 | @end deffn |
| 4681 | |
| 4682 | @deffn {Scheme Procedure} bytevector? obj |
| 4683 | @deffnx {C Function} scm_bytevector_p (obj) |
| 4684 | Return true if @var{obj} is a bytevector. |
| 4685 | @end deffn |
| 4686 | |
| 4687 | @deftypefn {C Function} int scm_is_bytevector (SCM obj) |
| 4688 | Equivalent to @code{scm_is_true (scm_bytevector_p (obj))}. |
| 4689 | @end deftypefn |
| 4690 | |
| 4691 | @deffn {Scheme Procedure} bytevector-length bv |
| 4692 | @deffnx {C Function} scm_bytevector_length (bv) |
| 4693 | Return the length in bytes of bytevector @var{bv}. |
| 4694 | @end deffn |
| 4695 | |
| 4696 | @deftypefn {C Function} size_t scm_c_bytevector_length (SCM bv) |
| 4697 | Likewise, return the length in bytes of bytevector @var{bv}. |
| 4698 | @end deftypefn |
| 4699 | |
| 4700 | @deffn {Scheme Procedure} bytevector=? bv1 bv2 |
| 4701 | @deffnx {C Function} scm_bytevector_eq_p (bv1, bv2) |
| 4702 | Return is @var{bv1} equals to @var{bv2}---i.e., if they have the same |
| 4703 | length and contents. |
| 4704 | @end deffn |
| 4705 | |
| 4706 | @deffn {Scheme Procedure} bytevector-fill! bv fill |
| 4707 | @deffnx {C Function} scm_bytevector_fill_x (bv, fill) |
| 4708 | Fill bytevector @var{bv} with @var{fill}, a byte. |
| 4709 | @end deffn |
| 4710 | |
| 4711 | @deffn {Scheme Procedure} bytevector-copy! source source-start target target-start len |
| 4712 | @deffnx {C Function} scm_bytevector_copy_x (source, source_start, target, target_start, len) |
| 4713 | Copy @var{len} bytes from @var{source} into @var{target}, starting |
| 4714 | reading from @var{source-start} (a positive index within @var{source}) |
| 4715 | and start writing at @var{target-start}. It is permitted for the |
| 4716 | @var{source} and @var{target} regions to overlap. |
| 4717 | @end deffn |
| 4718 | |
| 4719 | @deffn {Scheme Procedure} bytevector-copy bv |
| 4720 | @deffnx {C Function} scm_bytevector_copy (bv) |
| 4721 | Return a newly allocated copy of @var{bv}. |
| 4722 | @end deffn |
| 4723 | |
| 4724 | @deftypefn {C Function} scm_t_uint8 scm_c_bytevector_ref (SCM bv, size_t index) |
| 4725 | Return the byte at @var{index} in bytevector @var{bv}. |
| 4726 | @end deftypefn |
| 4727 | |
| 4728 | @deftypefn {C Function} void scm_c_bytevector_set_x (SCM bv, size_t index, scm_t_uint8 value) |
| 4729 | Set the byte at @var{index} in @var{bv} to @var{value}. |
| 4730 | @end deftypefn |
| 4731 | |
| 4732 | Low-level C macros are available. They do not perform any |
| 4733 | type-checking; as such they should be used with care. |
| 4734 | |
| 4735 | @deftypefn {C Macro} size_t SCM_BYTEVECTOR_LENGTH (bv) |
| 4736 | Return the length in bytes of bytevector @var{bv}. |
| 4737 | @end deftypefn |
| 4738 | |
| 4739 | @deftypefn {C Macro} {signed char *} SCM_BYTEVECTOR_CONTENTS (bv) |
| 4740 | Return a pointer to the contents of bytevector @var{bv}. |
| 4741 | @end deftypefn |
| 4742 | |
| 4743 | |
| 4744 | @node Bytevectors as Integers |
| 4745 | @subsubsection Interpreting Bytevector Contents as Integers |
| 4746 | |
| 4747 | The contents of a bytevector can be interpreted as a sequence of |
| 4748 | integers of any given size, sign, and endianness. |
| 4749 | |
| 4750 | @lisp |
| 4751 | (let ((bv (make-bytevector 4))) |
| 4752 | (bytevector-u8-set! bv 0 #x12) |
| 4753 | (bytevector-u8-set! bv 1 #x34) |
| 4754 | (bytevector-u8-set! bv 2 #x56) |
| 4755 | (bytevector-u8-set! bv 3 #x78) |
| 4756 | |
| 4757 | (map (lambda (number) |
| 4758 | (number->string number 16)) |
| 4759 | (list (bytevector-u8-ref bv 0) |
| 4760 | (bytevector-u16-ref bv 0 (endianness big)) |
| 4761 | (bytevector-u32-ref bv 0 (endianness little))))) |
| 4762 | |
| 4763 | @result{} ("12" "1234" "78563412") |
| 4764 | @end lisp |
| 4765 | |
| 4766 | The most generic procedures to interpret bytevector contents as integers |
| 4767 | are described below. |
| 4768 | |
| 4769 | @deffn {Scheme Procedure} bytevector-uint-ref bv index endianness size |
| 4770 | @deffnx {C Function} scm_bytevector_uint_ref (bv, index, endianness, size) |
| 4771 | Return the @var{size}-byte long unsigned integer at index @var{index} in |
| 4772 | @var{bv}, decoded according to @var{endianness}. |
| 4773 | @end deffn |
| 4774 | |
| 4775 | @deffn {Scheme Procedure} bytevector-sint-ref bv index endianness size |
| 4776 | @deffnx {C Function} scm_bytevector_sint_ref (bv, index, endianness, size) |
| 4777 | Return the @var{size}-byte long signed integer at index @var{index} in |
| 4778 | @var{bv}, decoded according to @var{endianness}. |
| 4779 | @end deffn |
| 4780 | |
| 4781 | @deffn {Scheme Procedure} bytevector-uint-set! bv index value endianness size |
| 4782 | @deffnx {C Function} scm_bytevector_uint_set_x (bv, index, value, endianness, size) |
| 4783 | Set the @var{size}-byte long unsigned integer at @var{index} to |
| 4784 | @var{value}, encoded according to @var{endianness}. |
| 4785 | @end deffn |
| 4786 | |
| 4787 | @deffn {Scheme Procedure} bytevector-sint-set! bv index value endianness size |
| 4788 | @deffnx {C Function} scm_bytevector_sint_set_x (bv, index, value, endianness, size) |
| 4789 | Set the @var{size}-byte long signed integer at @var{index} to |
| 4790 | @var{value}, encoded according to @var{endianness}. |
| 4791 | @end deffn |
| 4792 | |
| 4793 | The following procedures are similar to the ones above, but specialized |
| 4794 | to a given integer size: |
| 4795 | |
| 4796 | @deffn {Scheme Procedure} bytevector-u8-ref bv index |
| 4797 | @deffnx {Scheme Procedure} bytevector-s8-ref bv index |
| 4798 | @deffnx {Scheme Procedure} bytevector-u16-ref bv index endianness |
| 4799 | @deffnx {Scheme Procedure} bytevector-s16-ref bv index endianness |
| 4800 | @deffnx {Scheme Procedure} bytevector-u32-ref bv index endianness |
| 4801 | @deffnx {Scheme Procedure} bytevector-s32-ref bv index endianness |
| 4802 | @deffnx {Scheme Procedure} bytevector-u64-ref bv index endianness |
| 4803 | @deffnx {Scheme Procedure} bytevector-s64-ref bv index endianness |
| 4804 | @deffnx {C Function} scm_bytevector_u8_ref (bv, index) |
| 4805 | @deffnx {C Function} scm_bytevector_s8_ref (bv, index) |
| 4806 | @deffnx {C Function} scm_bytevector_u16_ref (bv, index, endianness) |
| 4807 | @deffnx {C Function} scm_bytevector_s16_ref (bv, index, endianness) |
| 4808 | @deffnx {C Function} scm_bytevector_u32_ref (bv, index, endianness) |
| 4809 | @deffnx {C Function} scm_bytevector_s32_ref (bv, index, endianness) |
| 4810 | @deffnx {C Function} scm_bytevector_u64_ref (bv, index, endianness) |
| 4811 | @deffnx {C Function} scm_bytevector_s64_ref (bv, index, endianness) |
| 4812 | Return the unsigned @var{n}-bit (signed) integer (where @var{n} is 8, |
| 4813 | 16, 32 or 64) from @var{bv} at @var{index}, decoded according to |
| 4814 | @var{endianness}. |
| 4815 | @end deffn |
| 4816 | |
| 4817 | @deffn {Scheme Procedure} bytevector-u8-set! bv index value |
| 4818 | @deffnx {Scheme Procedure} bytevector-s8-set! bv index value |
| 4819 | @deffnx {Scheme Procedure} bytevector-u16-set! bv index value endianness |
| 4820 | @deffnx {Scheme Procedure} bytevector-s16-set! bv index value endianness |
| 4821 | @deffnx {Scheme Procedure} bytevector-u32-set! bv index value endianness |
| 4822 | @deffnx {Scheme Procedure} bytevector-s32-set! bv index value endianness |
| 4823 | @deffnx {Scheme Procedure} bytevector-u64-set! bv index value endianness |
| 4824 | @deffnx {Scheme Procedure} bytevector-s64-set! bv index value endianness |
| 4825 | @deffnx {C Function} scm_bytevector_u8_set_x (bv, index, value) |
| 4826 | @deffnx {C Function} scm_bytevector_s8_set_x (bv, index, value) |
| 4827 | @deffnx {C Function} scm_bytevector_u16_set_x (bv, index, value, endianness) |
| 4828 | @deffnx {C Function} scm_bytevector_s16_set_x (bv, index, value, endianness) |
| 4829 | @deffnx {C Function} scm_bytevector_u32_set_x (bv, index, value, endianness) |
| 4830 | @deffnx {C Function} scm_bytevector_s32_set_x (bv, index, value, endianness) |
| 4831 | @deffnx {C Function} scm_bytevector_u64_set_x (bv, index, value, endianness) |
| 4832 | @deffnx {C Function} scm_bytevector_s64_set_x (bv, index, value, endianness) |
| 4833 | Store @var{value} as an @var{n}-bit (signed) integer (where @var{n} is |
| 4834 | 8, 16, 32 or 64) in @var{bv} at @var{index}, encoded according to |
| 4835 | @var{endianness}. |
| 4836 | @end deffn |
| 4837 | |
| 4838 | Finally, a variant specialized for the host's endianness is available |
| 4839 | for each of these functions (with the exception of the @code{u8} |
| 4840 | accessors, for obvious reasons): |
| 4841 | |
| 4842 | @deffn {Scheme Procedure} bytevector-u16-native-ref bv index |
| 4843 | @deffnx {Scheme Procedure} bytevector-s16-native-ref bv index |
| 4844 | @deffnx {Scheme Procedure} bytevector-u32-native-ref bv index |
| 4845 | @deffnx {Scheme Procedure} bytevector-s32-native-ref bv index |
| 4846 | @deffnx {Scheme Procedure} bytevector-u64-native-ref bv index |
| 4847 | @deffnx {Scheme Procedure} bytevector-s64-native-ref bv index |
| 4848 | @deffnx {C Function} scm_bytevector_u16_native_ref (bv, index) |
| 4849 | @deffnx {C Function} scm_bytevector_s16_native_ref (bv, index) |
| 4850 | @deffnx {C Function} scm_bytevector_u32_native_ref (bv, index) |
| 4851 | @deffnx {C Function} scm_bytevector_s32_native_ref (bv, index) |
| 4852 | @deffnx {C Function} scm_bytevector_u64_native_ref (bv, index) |
| 4853 | @deffnx {C Function} scm_bytevector_s64_native_ref (bv, index) |
| 4854 | Return the unsigned @var{n}-bit (signed) integer (where @var{n} is 8, |
| 4855 | 16, 32 or 64) from @var{bv} at @var{index}, decoded according to the |
| 4856 | host's native endianness. |
| 4857 | @end deffn |
| 4858 | |
| 4859 | @deffn {Scheme Procedure} bytevector-u16-native-set! bv index value |
| 4860 | @deffnx {Scheme Procedure} bytevector-s16-native-set! bv index value |
| 4861 | @deffnx {Scheme Procedure} bytevector-u32-native-set! bv index value |
| 4862 | @deffnx {Scheme Procedure} bytevector-s32-native-set! bv index value |
| 4863 | @deffnx {Scheme Procedure} bytevector-u64-native-set! bv index value |
| 4864 | @deffnx {Scheme Procedure} bytevector-s64-native-set! bv index value |
| 4865 | @deffnx {C Function} scm_bytevector_u16_native_set_x (bv, index, value) |
| 4866 | @deffnx {C Function} scm_bytevector_s16_native_set_x (bv, index, value) |
| 4867 | @deffnx {C Function} scm_bytevector_u32_native_set_x (bv, index, value) |
| 4868 | @deffnx {C Function} scm_bytevector_s32_native_set_x (bv, index, value) |
| 4869 | @deffnx {C Function} scm_bytevector_u64_native_set_x (bv, index, value) |
| 4870 | @deffnx {C Function} scm_bytevector_s64_native_set_x (bv, index, value) |
| 4871 | Store @var{value} as an @var{n}-bit (signed) integer (where @var{n} is |
| 4872 | 8, 16, 32 or 64) in @var{bv} at @var{index}, encoded according to the |
| 4873 | host's native endianness. |
| 4874 | @end deffn |
| 4875 | |
| 4876 | |
| 4877 | @node Bytevectors and Integer Lists |
| 4878 | @subsubsection Converting Bytevectors to/from Integer Lists |
| 4879 | |
| 4880 | Bytevector contents can readily be converted to/from lists of signed or |
| 4881 | unsigned integers: |
| 4882 | |
| 4883 | @lisp |
| 4884 | (bytevector->sint-list (u8-list->bytevector (make-list 4 255)) |
| 4885 | (endianness little) 2) |
| 4886 | @result{} (-1 -1) |
| 4887 | @end lisp |
| 4888 | |
| 4889 | @deffn {Scheme Procedure} bytevector->u8-list bv |
| 4890 | @deffnx {C Function} scm_bytevector_to_u8_list (bv) |
| 4891 | Return a newly allocated list of unsigned 8-bit integers from the |
| 4892 | contents of @var{bv}. |
| 4893 | @end deffn |
| 4894 | |
| 4895 | @deffn {Scheme Procedure} u8-list->bytevector lst |
| 4896 | @deffnx {C Function} scm_u8_list_to_bytevector (lst) |
| 4897 | Return a newly allocated bytevector consisting of the unsigned 8-bit |
| 4898 | integers listed in @var{lst}. |
| 4899 | @end deffn |
| 4900 | |
| 4901 | @deffn {Scheme Procedure} bytevector->uint-list bv endianness size |
| 4902 | @deffnx {C Function} scm_bytevector_to_uint_list (bv, endianness, size) |
| 4903 | Return a list of unsigned integers of @var{size} bytes representing the |
| 4904 | contents of @var{bv}, decoded according to @var{endianness}. |
| 4905 | @end deffn |
| 4906 | |
| 4907 | @deffn {Scheme Procedure} bytevector->sint-list bv endianness size |
| 4908 | @deffnx {C Function} scm_bytevector_to_sint_list (bv, endianness, size) |
| 4909 | Return a list of signed integers of @var{size} bytes representing the |
| 4910 | contents of @var{bv}, decoded according to @var{endianness}. |
| 4911 | @end deffn |
| 4912 | |
| 4913 | @deffn {Scheme Procedure} uint-list->bytevector lst endianness size |
| 4914 | @deffnx {C Function} scm_uint_list_to_bytevector (lst, endianness, size) |
| 4915 | Return a new bytevector containing the unsigned integers listed in |
| 4916 | @var{lst} and encoded on @var{size} bytes according to @var{endianness}. |
| 4917 | @end deffn |
| 4918 | |
| 4919 | @deffn {Scheme Procedure} sint-list->bytevector lst endianness size |
| 4920 | @deffnx {C Function} scm_sint_list_to_bytevector (lst, endianness, size) |
| 4921 | Return a new bytevector containing the signed integers listed in |
| 4922 | @var{lst} and encoded on @var{size} bytes according to @var{endianness}. |
| 4923 | @end deffn |
| 4924 | |
| 4925 | @node Bytevectors as Floats |
| 4926 | @subsubsection Interpreting Bytevector Contents as Floating Point Numbers |
| 4927 | |
| 4928 | @cindex IEEE-754 floating point numbers |
| 4929 | |
| 4930 | Bytevector contents can also be accessed as IEEE-754 single- or |
| 4931 | double-precision floating point numbers (respectively 32 and 64-bit |
| 4932 | long) using the procedures described here. |
| 4933 | |
| 4934 | @deffn {Scheme Procedure} bytevector-ieee-single-ref bv index endianness |
| 4935 | @deffnx {Scheme Procedure} bytevector-ieee-double-ref bv index endianness |
| 4936 | @deffnx {C Function} scm_bytevector_ieee_single_ref (bv, index, endianness) |
| 4937 | @deffnx {C Function} scm_bytevector_ieee_double_ref (bv, index, endianness) |
| 4938 | Return the IEEE-754 single-precision floating point number from @var{bv} |
| 4939 | at @var{index} according to @var{endianness}. |
| 4940 | @end deffn |
| 4941 | |
| 4942 | @deffn {Scheme Procedure} bytevector-ieee-single-set! bv index value endianness |
| 4943 | @deffnx {Scheme Procedure} bytevector-ieee-double-set! bv index value endianness |
| 4944 | @deffnx {C Function} scm_bytevector_ieee_single_set_x (bv, index, value, endianness) |
| 4945 | @deffnx {C Function} scm_bytevector_ieee_double_set_x (bv, index, value, endianness) |
| 4946 | Store real number @var{value} in @var{bv} at @var{index} according to |
| 4947 | @var{endianness}. |
| 4948 | @end deffn |
| 4949 | |
| 4950 | Specialized procedures are also available: |
| 4951 | |
| 4952 | @deffn {Scheme Procedure} bytevector-ieee-single-native-ref bv index |
| 4953 | @deffnx {Scheme Procedure} bytevector-ieee-double-native-ref bv index |
| 4954 | @deffnx {C Function} scm_bytevector_ieee_single_native_ref (bv, index) |
| 4955 | @deffnx {C Function} scm_bytevector_ieee_double_native_ref (bv, index) |
| 4956 | Return the IEEE-754 single-precision floating point number from @var{bv} |
| 4957 | at @var{index} according to the host's native endianness. |
| 4958 | @end deffn |
| 4959 | |
| 4960 | @deffn {Scheme Procedure} bytevector-ieee-single-native-set! bv index value |
| 4961 | @deffnx {Scheme Procedure} bytevector-ieee-double-native-set! bv index value |
| 4962 | @deffnx {C Function} scm_bytevector_ieee_single_native_set_x (bv, index, value) |
| 4963 | @deffnx {C Function} scm_bytevector_ieee_double_native_set_x (bv, index, value) |
| 4964 | Store real number @var{value} in @var{bv} at @var{index} according to |
| 4965 | the host's native endianness. |
| 4966 | @end deffn |
| 4967 | |
| 4968 | |
| 4969 | @node Bytevectors as Strings |
| 4970 | @subsubsection Interpreting Bytevector Contents as Unicode Strings |
| 4971 | |
| 4972 | @cindex Unicode string encoding |
| 4973 | |
| 4974 | Bytevector contents can also be interpreted as Unicode strings encoded |
| 4975 | in one of the most commonly available encoding formats. |
| 4976 | @xref{Representing Strings as Bytes}, for a more generic interface. |
| 4977 | |
| 4978 | @lisp |
| 4979 | (utf8->string (u8-list->bytevector '(99 97 102 101))) |
| 4980 | @result{} "cafe" |
| 4981 | |
| 4982 | (string->utf8 "caf@'e") ;; SMALL LATIN LETTER E WITH ACUTE ACCENT |
| 4983 | @result{} #vu8(99 97 102 195 169) |
| 4984 | @end lisp |
| 4985 | |
| 4986 | @deffn {Scheme Procedure} string->utf8 str |
| 4987 | @deffnx {Scheme Procedure} string->utf16 str [endianness] |
| 4988 | @deffnx {Scheme Procedure} string->utf32 str [endianness] |
| 4989 | @deffnx {C Function} scm_string_to_utf8 (str) |
| 4990 | @deffnx {C Function} scm_string_to_utf16 (str, endianness) |
| 4991 | @deffnx {C Function} scm_string_to_utf32 (str, endianness) |
| 4992 | Return a newly allocated bytevector that contains the UTF-8, UTF-16, or |
| 4993 | UTF-32 (aka. UCS-4) encoding of @var{str}. For UTF-16 and UTF-32, |
| 4994 | @var{endianness} should be the symbol @code{big} or @code{little}; when omitted, |
| 4995 | it defaults to big endian. |
| 4996 | @end deffn |
| 4997 | |
| 4998 | @deffn {Scheme Procedure} utf8->string utf |
| 4999 | @deffnx {Scheme Procedure} utf16->string utf [endianness] |
| 5000 | @deffnx {Scheme Procedure} utf32->string utf [endianness] |
| 5001 | @deffnx {C Function} scm_utf8_to_string (utf) |
| 5002 | @deffnx {C Function} scm_utf16_to_string (utf, endianness) |
| 5003 | @deffnx {C Function} scm_utf32_to_string (utf, endianness) |
| 5004 | Return a newly allocated string that contains from the UTF-8-, UTF-16-, |
| 5005 | or UTF-32-decoded contents of bytevector @var{utf}. For UTF-16 and UTF-32, |
| 5006 | @var{endianness} should be the symbol @code{big} or @code{little}; when omitted, |
| 5007 | it defaults to big endian. |
| 5008 | @end deffn |
| 5009 | |
| 5010 | @node Bytevectors as Arrays |
| 5011 | @subsubsection Accessing Bytevectors with the Array API |
| 5012 | |
| 5013 | As an extension to the R6RS, Guile allows bytevectors to be manipulated |
| 5014 | with the @dfn{array} procedures (@pxref{Arrays}). When using these |
| 5015 | APIs, bytes are accessed one at a time as 8-bit unsigned integers: |
| 5016 | |
| 5017 | @example |
| 5018 | (define bv #vu8(0 1 2 3)) |
| 5019 | |
| 5020 | (array? bv) |
| 5021 | @result{} #t |
| 5022 | |
| 5023 | (array-rank bv) |
| 5024 | @result{} 1 |
| 5025 | |
| 5026 | (array-ref bv 2) |
| 5027 | @result{} 2 |
| 5028 | |
| 5029 | ;; Note the different argument order on array-set!. |
| 5030 | (array-set! bv 77 2) |
| 5031 | (array-ref bv 2) |
| 5032 | @result{} 77 |
| 5033 | |
| 5034 | (array-type bv) |
| 5035 | @result{} vu8 |
| 5036 | @end example |
| 5037 | |
| 5038 | |
| 5039 | @node Bytevectors as Uniform Vectors |
| 5040 | @subsubsection Accessing Bytevectors with the SRFI-4 API |
| 5041 | |
| 5042 | Bytevectors may also be accessed with the SRFI-4 API. @xref{SRFI-4 and |
| 5043 | Bytevectors}, for more information. |
| 5044 | |
| 5045 | |
| 5046 | @node Symbols |
| 5047 | @subsection Symbols |
| 5048 | @tpindex Symbols |
| 5049 | |
| 5050 | Symbols in Scheme are widely used in three ways: as items of discrete |
| 5051 | data, as lookup keys for alists and hash tables, and to denote variable |
| 5052 | references. |
| 5053 | |
| 5054 | A @dfn{symbol} is similar to a string in that it is defined by a |
| 5055 | sequence of characters. The sequence of characters is known as the |
| 5056 | symbol's @dfn{name}. In the usual case --- that is, where the symbol's |
| 5057 | name doesn't include any characters that could be confused with other |
| 5058 | elements of Scheme syntax --- a symbol is written in a Scheme program by |
| 5059 | writing the sequence of characters that make up the name, @emph{without} |
| 5060 | any quotation marks or other special syntax. For example, the symbol |
| 5061 | whose name is ``multiply-by-2'' is written, simply: |
| 5062 | |
| 5063 | @lisp |
| 5064 | multiply-by-2 |
| 5065 | @end lisp |
| 5066 | |
| 5067 | Notice how this differs from a @emph{string} with contents |
| 5068 | ``multiply-by-2'', which is written with double quotation marks, like |
| 5069 | this: |
| 5070 | |
| 5071 | @lisp |
| 5072 | "multiply-by-2" |
| 5073 | @end lisp |
| 5074 | |
| 5075 | Looking beyond how they are written, symbols are different from strings |
| 5076 | in two important respects. |
| 5077 | |
| 5078 | The first important difference is uniqueness. If the same-looking |
| 5079 | string is read twice from two different places in a program, the result |
| 5080 | is two @emph{different} string objects whose contents just happen to be |
| 5081 | the same. If, on the other hand, the same-looking symbol is read twice |
| 5082 | from two different places in a program, the result is the @emph{same} |
| 5083 | symbol object both times. |
| 5084 | |
| 5085 | Given two read symbols, you can use @code{eq?} to test whether they are |
| 5086 | the same (that is, have the same name). @code{eq?} is the most |
| 5087 | efficient comparison operator in Scheme, and comparing two symbols like |
| 5088 | this is as fast as comparing, for example, two numbers. Given two |
| 5089 | strings, on the other hand, you must use @code{equal?} or |
| 5090 | @code{string=?}, which are much slower comparison operators, to |
| 5091 | determine whether the strings have the same contents. |
| 5092 | |
| 5093 | @lisp |
| 5094 | (define sym1 (quote hello)) |
| 5095 | (define sym2 (quote hello)) |
| 5096 | (eq? sym1 sym2) @result{} #t |
| 5097 | |
| 5098 | (define str1 "hello") |
| 5099 | (define str2 "hello") |
| 5100 | (eq? str1 str2) @result{} #f |
| 5101 | (equal? str1 str2) @result{} #t |
| 5102 | @end lisp |
| 5103 | |
| 5104 | The second important difference is that symbols, unlike strings, are not |
| 5105 | self-evaluating. This is why we need the @code{(quote @dots{})}s in the |
| 5106 | example above: @code{(quote hello)} evaluates to the symbol named |
| 5107 | "hello" itself, whereas an unquoted @code{hello} is @emph{read} as the |
| 5108 | symbol named "hello" and evaluated as a variable reference @dots{} about |
| 5109 | which more below (@pxref{Symbol Variables}). |
| 5110 | |
| 5111 | @menu |
| 5112 | * Symbol Data:: Symbols as discrete data. |
| 5113 | * Symbol Keys:: Symbols as lookup keys. |
| 5114 | * Symbol Variables:: Symbols as denoting variables. |
| 5115 | * Symbol Primitives:: Operations related to symbols. |
| 5116 | * Symbol Props:: Function slots and property lists. |
| 5117 | * Symbol Read Syntax:: Extended read syntax for symbols. |
| 5118 | * Symbol Uninterned:: Uninterned symbols. |
| 5119 | @end menu |
| 5120 | |
| 5121 | |
| 5122 | @node Symbol Data |
| 5123 | @subsubsection Symbols as Discrete Data |
| 5124 | |
| 5125 | Numbers and symbols are similar to the extent that they both lend |
| 5126 | themselves to @code{eq?} comparison. But symbols are more descriptive |
| 5127 | than numbers, because a symbol's name can be used directly to describe |
| 5128 | the concept for which that symbol stands. |
| 5129 | |
| 5130 | For example, imagine that you need to represent some colours in a |
| 5131 | computer program. Using numbers, you would have to choose arbitrarily |
| 5132 | some mapping between numbers and colours, and then take care to use that |
| 5133 | mapping consistently: |
| 5134 | |
| 5135 | @lisp |
| 5136 | ;; 1=red, 2=green, 3=purple |
| 5137 | |
| 5138 | (if (eq? (colour-of car) 1) |
| 5139 | ...) |
| 5140 | @end lisp |
| 5141 | |
| 5142 | @noindent |
| 5143 | You can make the mapping more explicit and the code more readable by |
| 5144 | defining constants: |
| 5145 | |
| 5146 | @lisp |
| 5147 | (define red 1) |
| 5148 | (define green 2) |
| 5149 | (define purple 3) |
| 5150 | |
| 5151 | (if (eq? (colour-of car) red) |
| 5152 | ...) |
| 5153 | @end lisp |
| 5154 | |
| 5155 | @noindent |
| 5156 | But the simplest and clearest approach is not to use numbers at all, but |
| 5157 | symbols whose names specify the colours that they refer to: |
| 5158 | |
| 5159 | @lisp |
| 5160 | (if (eq? (colour-of car) 'red) |
| 5161 | ...) |
| 5162 | @end lisp |
| 5163 | |
| 5164 | The descriptive advantages of symbols over numbers increase as the set |
| 5165 | of concepts that you want to describe grows. Suppose that a car object |
| 5166 | can have other properties as well, such as whether it has or uses: |
| 5167 | |
| 5168 | @itemize @bullet |
| 5169 | @item |
| 5170 | automatic or manual transmission |
| 5171 | @item |
| 5172 | leaded or unleaded fuel |
| 5173 | @item |
| 5174 | power steering (or not). |
| 5175 | @end itemize |
| 5176 | |
| 5177 | @noindent |
| 5178 | Then a car's combined property set could be naturally represented and |
| 5179 | manipulated as a list of symbols: |
| 5180 | |
| 5181 | @lisp |
| 5182 | (properties-of car1) |
| 5183 | @result{} |
| 5184 | (red manual unleaded power-steering) |
| 5185 | |
| 5186 | (if (memq 'power-steering (properties-of car1)) |
| 5187 | (display "Unfit people can drive this car.\n") |
| 5188 | (display "You'll need strong arms to drive this car!\n")) |
| 5189 | @print{} |
| 5190 | Unfit people can drive this car. |
| 5191 | @end lisp |
| 5192 | |
| 5193 | Remember, the fundamental property of symbols that we are relying on |
| 5194 | here is that an occurrence of @code{'red} in one part of a program is an |
| 5195 | @emph{indistinguishable} symbol from an occurrence of @code{'red} in |
| 5196 | another part of a program; this means that symbols can usefully be |
| 5197 | compared using @code{eq?}. At the same time, symbols have naturally |
| 5198 | descriptive names. This combination of efficiency and descriptive power |
| 5199 | makes them ideal for use as discrete data. |
| 5200 | |
| 5201 | |
| 5202 | @node Symbol Keys |
| 5203 | @subsubsection Symbols as Lookup Keys |
| 5204 | |
| 5205 | Given their efficiency and descriptive power, it is natural to use |
| 5206 | symbols as the keys in an association list or hash table. |
| 5207 | |
| 5208 | To illustrate this, consider a more structured representation of the car |
| 5209 | properties example from the preceding subsection. Rather than |
| 5210 | mixing all the properties up together in a flat list, we could use an |
| 5211 | association list like this: |
| 5212 | |
| 5213 | @lisp |
| 5214 | (define car1-properties '((colour . red) |
| 5215 | (transmission . manual) |
| 5216 | (fuel . unleaded) |
| 5217 | (steering . power-assisted))) |
| 5218 | @end lisp |
| 5219 | |
| 5220 | Notice how this structure is more explicit and extensible than the flat |
| 5221 | list. For example it makes clear that @code{manual} refers to the |
| 5222 | transmission rather than, say, the windows or the locking of the car. |
| 5223 | It also allows further properties to use the same symbols among their |
| 5224 | possible values without becoming ambiguous: |
| 5225 | |
| 5226 | @lisp |
| 5227 | (define car1-properties '((colour . red) |
| 5228 | (transmission . manual) |
| 5229 | (fuel . unleaded) |
| 5230 | (steering . power-assisted) |
| 5231 | (seat-colour . red) |
| 5232 | (locking . manual))) |
| 5233 | @end lisp |
| 5234 | |
| 5235 | With a representation like this, it is easy to use the efficient |
| 5236 | @code{assq-XXX} family of procedures (@pxref{Association Lists}) to |
| 5237 | extract or change individual pieces of information: |
| 5238 | |
| 5239 | @lisp |
| 5240 | (assq-ref car1-properties 'fuel) @result{} unleaded |
| 5241 | (assq-ref car1-properties 'transmission) @result{} manual |
| 5242 | |
| 5243 | (assq-set! car1-properties 'seat-colour 'black) |
| 5244 | @result{} |
| 5245 | ((colour . red) |
| 5246 | (transmission . manual) |
| 5247 | (fuel . unleaded) |
| 5248 | (steering . power-assisted) |
| 5249 | (seat-colour . black) |
| 5250 | (locking . manual))) |
| 5251 | @end lisp |
| 5252 | |
| 5253 | Hash tables also have keys, and exactly the same arguments apply to the |
| 5254 | use of symbols in hash tables as in association lists. The hash value |
| 5255 | that Guile uses to decide where to add a symbol-keyed entry to a hash |
| 5256 | table can be obtained by calling the @code{symbol-hash} procedure: |
| 5257 | |
| 5258 | @deffn {Scheme Procedure} symbol-hash symbol |
| 5259 | @deffnx {C Function} scm_symbol_hash (symbol) |
| 5260 | Return a hash value for @var{symbol}. |
| 5261 | @end deffn |
| 5262 | |
| 5263 | See @ref{Hash Tables} for information about hash tables in general, and |
| 5264 | for why you might choose to use a hash table rather than an association |
| 5265 | list. |
| 5266 | |
| 5267 | |
| 5268 | @node Symbol Variables |
| 5269 | @subsubsection Symbols as Denoting Variables |
| 5270 | |
| 5271 | When an unquoted symbol in a Scheme program is evaluated, it is |
| 5272 | interpreted as a variable reference, and the result of the evaluation is |
| 5273 | the appropriate variable's value. |
| 5274 | |
| 5275 | For example, when the expression @code{(string-length "abcd")} is read |
| 5276 | and evaluated, the sequence of characters @code{string-length} is read |
| 5277 | as the symbol whose name is "string-length". This symbol is associated |
| 5278 | with a variable whose value is the procedure that implements string |
| 5279 | length calculation. Therefore evaluation of the @code{string-length} |
| 5280 | symbol results in that procedure. |
| 5281 | |
| 5282 | The details of the connection between an unquoted symbol and the |
| 5283 | variable to which it refers are explained elsewhere. See @ref{Binding |
| 5284 | Constructs}, for how associations between symbols and variables are |
| 5285 | created, and @ref{Modules}, for how those associations are affected by |
| 5286 | Guile's module system. |
| 5287 | |
| 5288 | |
| 5289 | @node Symbol Primitives |
| 5290 | @subsubsection Operations Related to Symbols |
| 5291 | |
| 5292 | Given any Scheme value, you can determine whether it is a symbol using |
| 5293 | the @code{symbol?} primitive: |
| 5294 | |
| 5295 | @rnindex symbol? |
| 5296 | @deffn {Scheme Procedure} symbol? obj |
| 5297 | @deffnx {C Function} scm_symbol_p (obj) |
| 5298 | Return @code{#t} if @var{obj} is a symbol, otherwise return |
| 5299 | @code{#f}. |
| 5300 | @end deffn |
| 5301 | |
| 5302 | @deftypefn {C Function} int scm_is_symbol (SCM val) |
| 5303 | Equivalent to @code{scm_is_true (scm_symbol_p (val))}. |
| 5304 | @end deftypefn |
| 5305 | |
| 5306 | Once you know that you have a symbol, you can obtain its name as a |
| 5307 | string by calling @code{symbol->string}. Note that Guile differs by |
| 5308 | default from R5RS on the details of @code{symbol->string} as regards |
| 5309 | case-sensitivity: |
| 5310 | |
| 5311 | @rnindex symbol->string |
| 5312 | @deffn {Scheme Procedure} symbol->string s |
| 5313 | @deffnx {C Function} scm_symbol_to_string (s) |
| 5314 | Return the name of symbol @var{s} as a string. By default, Guile reads |
| 5315 | symbols case-sensitively, so the string returned will have the same case |
| 5316 | variation as the sequence of characters that caused @var{s} to be |
| 5317 | created. |
| 5318 | |
| 5319 | If Guile is set to read symbols case-insensitively (as specified by |
| 5320 | R5RS), and @var{s} comes into being as part of a literal expression |
| 5321 | (@pxref{Literal expressions,,,r5rs, The Revised^5 Report on Scheme}) or |
| 5322 | by a call to the @code{read} or @code{string-ci->symbol} procedures, |
| 5323 | Guile converts any alphabetic characters in the symbol's name to |
| 5324 | lower case before creating the symbol object, so the string returned |
| 5325 | here will be in lower case. |
| 5326 | |
| 5327 | If @var{s} was created by @code{string->symbol}, the case of characters |
| 5328 | in the string returned will be the same as that in the string that was |
| 5329 | passed to @code{string->symbol}, regardless of Guile's case-sensitivity |
| 5330 | setting at the time @var{s} was created. |
| 5331 | |
| 5332 | It is an error to apply mutation procedures like @code{string-set!} to |
| 5333 | strings returned by this procedure. |
| 5334 | @end deffn |
| 5335 | |
| 5336 | Most symbols are created by writing them literally in code. However it |
| 5337 | is also possible to create symbols programmatically using the following |
| 5338 | procedures: |
| 5339 | |
| 5340 | @deffn {Scheme Procedure} symbol char@dots{} |
| 5341 | @rnindex symbol |
| 5342 | Return a newly allocated symbol made from the given character arguments. |
| 5343 | |
| 5344 | @example |
| 5345 | (symbol #\x #\y #\z) @result{} xyz |
| 5346 | @end example |
| 5347 | @end deffn |
| 5348 | |
| 5349 | @deffn {Scheme Procedure} list->symbol lst |
| 5350 | @rnindex list->symbol |
| 5351 | Return a newly allocated symbol made from a list of characters. |
| 5352 | |
| 5353 | @example |
| 5354 | (list->symbol '(#\a #\b #\c)) @result{} abc |
| 5355 | @end example |
| 5356 | @end deffn |
| 5357 | |
| 5358 | @rnindex symbol-append |
| 5359 | @deffn {Scheme Procedure} symbol-append arg @dots{} |
| 5360 | Return a newly allocated symbol whose characters form the |
| 5361 | concatenation of the given symbols, @var{arg} @enddots{}. |
| 5362 | |
| 5363 | @example |
| 5364 | (let ((h 'hello)) |
| 5365 | (symbol-append h 'world)) |
| 5366 | @result{} helloworld |
| 5367 | @end example |
| 5368 | @end deffn |
| 5369 | |
| 5370 | @rnindex string->symbol |
| 5371 | @deffn {Scheme Procedure} string->symbol string |
| 5372 | @deffnx {C Function} scm_string_to_symbol (string) |
| 5373 | Return the symbol whose name is @var{string}. This procedure can create |
| 5374 | symbols with names containing special characters or letters in the |
| 5375 | non-standard case, but it is usually a bad idea to create such symbols |
| 5376 | because in some implementations of Scheme they cannot be read as |
| 5377 | themselves. |
| 5378 | @end deffn |
| 5379 | |
| 5380 | @deffn {Scheme Procedure} string-ci->symbol str |
| 5381 | @deffnx {C Function} scm_string_ci_to_symbol (str) |
| 5382 | Return the symbol whose name is @var{str}. If Guile is currently |
| 5383 | reading symbols case-insensitively, @var{str} is converted to lowercase |
| 5384 | before the returned symbol is looked up or created. |
| 5385 | @end deffn |
| 5386 | |
| 5387 | The following examples illustrate Guile's detailed behaviour as regards |
| 5388 | the case-sensitivity of symbols: |
| 5389 | |
| 5390 | @lisp |
| 5391 | (read-enable 'case-insensitive) ; R5RS compliant behaviour |
| 5392 | |
| 5393 | (symbol->string 'flying-fish) @result{} "flying-fish" |
| 5394 | (symbol->string 'Martin) @result{} "martin" |
| 5395 | (symbol->string |
| 5396 | (string->symbol "Malvina")) @result{} "Malvina" |
| 5397 | |
| 5398 | (eq? 'mISSISSIppi 'mississippi) @result{} #t |
| 5399 | (string->symbol "mISSISSIppi") @result{} mISSISSIppi |
| 5400 | (eq? 'bitBlt (string->symbol "bitBlt")) @result{} #f |
| 5401 | (eq? 'LolliPop |
| 5402 | (string->symbol (symbol->string 'LolliPop))) @result{} #t |
| 5403 | (string=? "K. Harper, M.D." |
| 5404 | (symbol->string |
| 5405 | (string->symbol "K. Harper, M.D."))) @result{} #t |
| 5406 | |
| 5407 | (read-disable 'case-insensitive) ; Guile default behaviour |
| 5408 | |
| 5409 | (symbol->string 'flying-fish) @result{} "flying-fish" |
| 5410 | (symbol->string 'Martin) @result{} "Martin" |
| 5411 | (symbol->string |
| 5412 | (string->symbol "Malvina")) @result{} "Malvina" |
| 5413 | |
| 5414 | (eq? 'mISSISSIppi 'mississippi) @result{} #f |
| 5415 | (string->symbol "mISSISSIppi") @result{} mISSISSIppi |
| 5416 | (eq? 'bitBlt (string->symbol "bitBlt")) @result{} #t |
| 5417 | (eq? 'LolliPop |
| 5418 | (string->symbol (symbol->string 'LolliPop))) @result{} #t |
| 5419 | (string=? "K. Harper, M.D." |
| 5420 | (symbol->string |
| 5421 | (string->symbol "K. Harper, M.D."))) @result{} #t |
| 5422 | @end lisp |
| 5423 | |
| 5424 | From C, there are lower level functions that construct a Scheme symbol |
| 5425 | from a C string in the current locale encoding. |
| 5426 | |
| 5427 | When you want to do more from C, you should convert between symbols |
| 5428 | and strings using @code{scm_symbol_to_string} and |
| 5429 | @code{scm_string_to_symbol} and work with the strings. |
| 5430 | |
| 5431 | @deftypefn {C Function} SCM scm_from_latin1_symbol (const char *name) |
| 5432 | @deftypefnx {C Function} SCM scm_from_utf8_symbol (const char *name) |
| 5433 | Construct and return a Scheme symbol whose name is specified by the |
| 5434 | null-terminated C string @var{name}. These are appropriate when |
| 5435 | the C string is hard-coded in the source code. |
| 5436 | @end deftypefn |
| 5437 | |
| 5438 | @deftypefn {C Function} SCM scm_from_locale_symbol (const char *name) |
| 5439 | @deftypefnx {C Function} SCM scm_from_locale_symboln (const char *name, size_t len) |
| 5440 | Construct and return a Scheme symbol whose name is specified by |
| 5441 | @var{name}. For @code{scm_from_locale_symbol}, @var{name} must be null |
| 5442 | terminated; for @code{scm_from_locale_symboln} the length of @var{name} is |
| 5443 | specified explicitly by @var{len}. |
| 5444 | |
| 5445 | Note that these functions should @emph{not} be used when @var{name} is a |
| 5446 | C string constant, because there is no guarantee that the current locale |
| 5447 | will match that of the execution character set, used for string and |
| 5448 | character constants. Most modern C compilers use UTF-8 by default, so |
| 5449 | in such cases we recommend @code{scm_from_utf8_symbol}. |
| 5450 | @end deftypefn |
| 5451 | |
| 5452 | @deftypefn {C Function} SCM scm_take_locale_symbol (char *str) |
| 5453 | @deftypefnx {C Function} SCM scm_take_locale_symboln (char *str, size_t len) |
| 5454 | Like @code{scm_from_locale_symbol} and @code{scm_from_locale_symboln}, |
| 5455 | respectively, but also frees @var{str} with @code{free} eventually. |
| 5456 | Thus, you can use this function when you would free @var{str} anyway |
| 5457 | immediately after creating the Scheme string. In certain cases, Guile |
| 5458 | can then use @var{str} directly as its internal representation. |
| 5459 | @end deftypefn |
| 5460 | |
| 5461 | The size of a symbol can also be obtained from C: |
| 5462 | |
| 5463 | @deftypefn {C Function} size_t scm_c_symbol_length (SCM sym) |
| 5464 | Return the number of characters in @var{sym}. |
| 5465 | @end deftypefn |
| 5466 | |
| 5467 | Finally, some applications, especially those that generate new Scheme |
| 5468 | code dynamically, need to generate symbols for use in the generated |
| 5469 | code. The @code{gensym} primitive meets this need: |
| 5470 | |
| 5471 | @deffn {Scheme Procedure} gensym [prefix] |
| 5472 | @deffnx {C Function} scm_gensym (prefix) |
| 5473 | Create a new symbol with a name constructed from a prefix and a counter |
| 5474 | value. The string @var{prefix} can be specified as an optional |
| 5475 | argument. Default prefix is @samp{@w{ g}}. The counter is increased by 1 |
| 5476 | at each call. There is no provision for resetting the counter. |
| 5477 | @end deffn |
| 5478 | |
| 5479 | The symbols generated by @code{gensym} are @emph{likely} to be unique, |
| 5480 | since their names begin with a space and it is only otherwise possible |
| 5481 | to generate such symbols if a programmer goes out of their way to do |
| 5482 | so. Uniqueness can be guaranteed by instead using uninterned symbols |
| 5483 | (@pxref{Symbol Uninterned}), though they can't be usefully written out |
| 5484 | and read back in. |
| 5485 | |
| 5486 | |
| 5487 | @node Symbol Props |
| 5488 | @subsubsection Function Slots and Property Lists |
| 5489 | |
| 5490 | In traditional Lisp dialects, symbols are often understood as having |
| 5491 | three kinds of value at once: |
| 5492 | |
| 5493 | @itemize @bullet |
| 5494 | @item |
| 5495 | a @dfn{variable} value, which is used when the symbol appears in |
| 5496 | code in a variable reference context |
| 5497 | |
| 5498 | @item |
| 5499 | a @dfn{function} value, which is used when the symbol appears in |
| 5500 | code in a function name position (i.e.@: as the first element in an |
| 5501 | unquoted list) |
| 5502 | |
| 5503 | @item |
| 5504 | a @dfn{property list} value, which is used when the symbol is given as |
| 5505 | the first argument to Lisp's @code{put} or @code{get} functions. |
| 5506 | @end itemize |
| 5507 | |
| 5508 | Although Scheme (as one of its simplifications with respect to Lisp) |
| 5509 | does away with the distinction between variable and function namespaces, |
| 5510 | Guile currently retains some elements of the traditional structure in |
| 5511 | case they turn out to be useful when implementing translators for other |
| 5512 | languages, in particular Emacs Lisp. |
| 5513 | |
| 5514 | Specifically, Guile symbols have two extra slots, one for a symbol's |
| 5515 | property list, and one for its ``function value.'' The following procedures |
| 5516 | are provided to access these slots. |
| 5517 | |
| 5518 | @deffn {Scheme Procedure} symbol-fref symbol |
| 5519 | @deffnx {C Function} scm_symbol_fref (symbol) |
| 5520 | Return the contents of @var{symbol}'s @dfn{function slot}. |
| 5521 | @end deffn |
| 5522 | |
| 5523 | @deffn {Scheme Procedure} symbol-fset! symbol value |
| 5524 | @deffnx {C Function} scm_symbol_fset_x (symbol, value) |
| 5525 | Set the contents of @var{symbol}'s function slot to @var{value}. |
| 5526 | @end deffn |
| 5527 | |
| 5528 | @deffn {Scheme Procedure} symbol-pref symbol |
| 5529 | @deffnx {C Function} scm_symbol_pref (symbol) |
| 5530 | Return the @dfn{property list} currently associated with @var{symbol}. |
| 5531 | @end deffn |
| 5532 | |
| 5533 | @deffn {Scheme Procedure} symbol-pset! symbol value |
| 5534 | @deffnx {C Function} scm_symbol_pset_x (symbol, value) |
| 5535 | Set @var{symbol}'s property list to @var{value}. |
| 5536 | @end deffn |
| 5537 | |
| 5538 | @deffn {Scheme Procedure} symbol-property sym prop |
| 5539 | From @var{sym}'s property list, return the value for property |
| 5540 | @var{prop}. The assumption is that @var{sym}'s property list is an |
| 5541 | association list whose keys are distinguished from each other using |
| 5542 | @code{equal?}; @var{prop} should be one of the keys in that list. If |
| 5543 | the property list has no entry for @var{prop}, @code{symbol-property} |
| 5544 | returns @code{#f}. |
| 5545 | @end deffn |
| 5546 | |
| 5547 | @deffn {Scheme Procedure} set-symbol-property! sym prop val |
| 5548 | In @var{sym}'s property list, set the value for property @var{prop} to |
| 5549 | @var{val}, or add a new entry for @var{prop}, with value @var{val}, if |
| 5550 | none already exists. For the structure of the property list, see |
| 5551 | @code{symbol-property}. |
| 5552 | @end deffn |
| 5553 | |
| 5554 | @deffn {Scheme Procedure} symbol-property-remove! sym prop |
| 5555 | From @var{sym}'s property list, remove the entry for property |
| 5556 | @var{prop}, if there is one. For the structure of the property list, |
| 5557 | see @code{symbol-property}. |
| 5558 | @end deffn |
| 5559 | |
| 5560 | Support for these extra slots may be removed in a future release, and it |
| 5561 | is probably better to avoid using them. For a more modern and Schemely |
| 5562 | approach to properties, see @ref{Object Properties}. |
| 5563 | |
| 5564 | |
| 5565 | @node Symbol Read Syntax |
| 5566 | @subsubsection Extended Read Syntax for Symbols |
| 5567 | |
| 5568 | @cindex r7rs-symbols |
| 5569 | |
| 5570 | The read syntax for a symbol is a sequence of letters, digits, and |
| 5571 | @dfn{extended alphabetic characters}, beginning with a character that |
| 5572 | cannot begin a number. In addition, the special cases of @code{+}, |
| 5573 | @code{-}, and @code{...} are read as symbols even though numbers can |
| 5574 | begin with @code{+}, @code{-} or @code{.}. |
| 5575 | |
| 5576 | Extended alphabetic characters may be used within identifiers as if |
| 5577 | they were letters. The set of extended alphabetic characters is: |
| 5578 | |
| 5579 | @example |
| 5580 | ! $ % & * + - . / : < = > ? @@ ^ _ ~ |
| 5581 | @end example |
| 5582 | |
| 5583 | In addition to the standard read syntax defined above (which is taken |
| 5584 | from R5RS (@pxref{Formal syntax,,,r5rs,The Revised^5 Report on |
| 5585 | Scheme})), Guile provides an extended symbol read syntax that allows the |
| 5586 | inclusion of unusual characters such as space characters, newlines and |
| 5587 | parentheses. If (for whatever reason) you need to write a symbol |
| 5588 | containing characters not mentioned above, you can do so as follows. |
| 5589 | |
| 5590 | @itemize @bullet |
| 5591 | @item |
| 5592 | Begin the symbol with the characters @code{#@{}, |
| 5593 | |
| 5594 | @item |
| 5595 | write the characters of the symbol and |
| 5596 | |
| 5597 | @item |
| 5598 | finish the symbol with the characters @code{@}#}. |
| 5599 | @end itemize |
| 5600 | |
| 5601 | Here are a few examples of this form of read syntax. The first symbol |
| 5602 | needs to use extended syntax because it contains a space character, the |
| 5603 | second because it contains a line break, and the last because it looks |
| 5604 | like a number. |
| 5605 | |
| 5606 | @lisp |
| 5607 | #@{foo bar@}# |
| 5608 | |
| 5609 | #@{what |
| 5610 | ever@}# |
| 5611 | |
| 5612 | #@{4242@}# |
| 5613 | @end lisp |
| 5614 | |
| 5615 | Although Guile provides this extended read syntax for symbols, |
| 5616 | widespread usage of it is discouraged because it is not portable and not |
| 5617 | very readable. |
| 5618 | |
| 5619 | Alternatively, if you enable the @code{r7rs-symbols} read option (see |
| 5620 | @pxref{Scheme Read}), you can write arbitrary symbols using the same |
| 5621 | notation used for strings, except delimited by vertical bars instead of |
| 5622 | double quotes. |
| 5623 | |
| 5624 | @example |
| 5625 | |foo bar| |
| 5626 | |\x3BB; is a greek lambda| |
| 5627 | |\| is a vertical bar| |
| 5628 | @end example |
| 5629 | |
| 5630 | Note that there's also an @code{r7rs-symbols} print option |
| 5631 | (@pxref{Scheme Write}). To enable the use of this notation, evaluate |
| 5632 | one or both of the following expressions: |
| 5633 | |
| 5634 | @example |
| 5635 | (read-enable 'r7rs-symbols) |
| 5636 | (print-enable 'r7rs-symbols) |
| 5637 | @end example |
| 5638 | |
| 5639 | |
| 5640 | @node Symbol Uninterned |
| 5641 | @subsubsection Uninterned Symbols |
| 5642 | |
| 5643 | What makes symbols useful is that they are automatically kept unique. |
| 5644 | There are no two symbols that are distinct objects but have the same |
| 5645 | name. But of course, there is no rule without exception. In addition |
| 5646 | to the normal symbols that have been discussed up to now, you can also |
| 5647 | create special @dfn{uninterned} symbols that behave slightly |
| 5648 | differently. |
| 5649 | |
| 5650 | To understand what is different about them and why they might be useful, |
| 5651 | we look at how normal symbols are actually kept unique. |
| 5652 | |
| 5653 | Whenever Guile wants to find the symbol with a specific name, for |
| 5654 | example during @code{read} or when executing @code{string->symbol}, it |
| 5655 | first looks into a table of all existing symbols to find out whether a |
| 5656 | symbol with the given name already exists. When this is the case, Guile |
| 5657 | just returns that symbol. When not, a new symbol with the name is |
| 5658 | created and entered into the table so that it can be found later. |
| 5659 | |
| 5660 | Sometimes you might want to create a symbol that is guaranteed `fresh', |
| 5661 | i.e.@: a symbol that did not exist previously. You might also want to |
| 5662 | somehow guarantee that no one else will ever unintentionally stumble |
| 5663 | across your symbol in the future. These properties of a symbol are |
| 5664 | often needed when generating code during macro expansion. When |
| 5665 | introducing new temporary variables, you want to guarantee that they |
| 5666 | don't conflict with variables in other people's code. |
| 5667 | |
| 5668 | The simplest way to arrange for this is to create a new symbol but |
| 5669 | not enter it into the global table of all symbols. That way, no one |
| 5670 | will ever get access to your symbol by chance. Symbols that are not in |
| 5671 | the table are called @dfn{uninterned}. Of course, symbols that |
| 5672 | @emph{are} in the table are called @dfn{interned}. |
| 5673 | |
| 5674 | You create new uninterned symbols with the function @code{make-symbol}. |
| 5675 | You can test whether a symbol is interned or not with |
| 5676 | @code{symbol-interned?}. |
| 5677 | |
| 5678 | Uninterned symbols break the rule that the name of a symbol uniquely |
| 5679 | identifies the symbol object. Because of this, they can not be written |
| 5680 | out and read back in like interned symbols. Currently, Guile has no |
| 5681 | support for reading uninterned symbols. Note that the function |
| 5682 | @code{gensym} does not return uninterned symbols for this reason. |
| 5683 | |
| 5684 | @deffn {Scheme Procedure} make-symbol name |
| 5685 | @deffnx {C Function} scm_make_symbol (name) |
| 5686 | Return a new uninterned symbol with the name @var{name}. The returned |
| 5687 | symbol is guaranteed to be unique and future calls to |
| 5688 | @code{string->symbol} will not return it. |
| 5689 | @end deffn |
| 5690 | |
| 5691 | @deffn {Scheme Procedure} symbol-interned? symbol |
| 5692 | @deffnx {C Function} scm_symbol_interned_p (symbol) |
| 5693 | Return @code{#t} if @var{symbol} is interned, otherwise return |
| 5694 | @code{#f}. |
| 5695 | @end deffn |
| 5696 | |
| 5697 | For example: |
| 5698 | |
| 5699 | @lisp |
| 5700 | (define foo-1 (string->symbol "foo")) |
| 5701 | (define foo-2 (string->symbol "foo")) |
| 5702 | (define foo-3 (make-symbol "foo")) |
| 5703 | (define foo-4 (make-symbol "foo")) |
| 5704 | |
| 5705 | (eq? foo-1 foo-2) |
| 5706 | @result{} #t |
| 5707 | ; Two interned symbols with the same name are the same object, |
| 5708 | |
| 5709 | (eq? foo-1 foo-3) |
| 5710 | @result{} #f |
| 5711 | ; but a call to make-symbol with the same name returns a |
| 5712 | ; distinct object. |
| 5713 | |
| 5714 | (eq? foo-3 foo-4) |
| 5715 | @result{} #f |
| 5716 | ; A call to make-symbol always returns a new object, even for |
| 5717 | ; the same name. |
| 5718 | |
| 5719 | foo-3 |
| 5720 | @result{} #<uninterned-symbol foo 8085290> |
| 5721 | ; Uninterned symbols print differently from interned symbols, |
| 5722 | |
| 5723 | (symbol? foo-3) |
| 5724 | @result{} #t |
| 5725 | ; but they are still symbols, |
| 5726 | |
| 5727 | (symbol-interned? foo-3) |
| 5728 | @result{} #f |
| 5729 | ; just not interned. |
| 5730 | @end lisp |
| 5731 | |
| 5732 | |
| 5733 | @node Keywords |
| 5734 | @subsection Keywords |
| 5735 | @tpindex Keywords |
| 5736 | |
| 5737 | Keywords are self-evaluating objects with a convenient read syntax that |
| 5738 | makes them easy to type. |
| 5739 | |
| 5740 | Guile's keyword support conforms to R5RS, and adds a (switchable) read |
| 5741 | syntax extension to permit keywords to begin with @code{:} as well as |
| 5742 | @code{#:}, or to end with @code{:}. |
| 5743 | |
| 5744 | @menu |
| 5745 | * Why Use Keywords?:: Motivation for keyword usage. |
| 5746 | * Coding With Keywords:: How to use keywords. |
| 5747 | * Keyword Read Syntax:: Read syntax for keywords. |
| 5748 | * Keyword Procedures:: Procedures for dealing with keywords. |
| 5749 | @end menu |
| 5750 | |
| 5751 | @node Why Use Keywords? |
| 5752 | @subsubsection Why Use Keywords? |
| 5753 | |
| 5754 | Keywords are useful in contexts where a program or procedure wants to be |
| 5755 | able to accept a large number of optional arguments without making its |
| 5756 | interface unmanageable. |
| 5757 | |
| 5758 | To illustrate this, consider a hypothetical @code{make-window} |
| 5759 | procedure, which creates a new window on the screen for drawing into |
| 5760 | using some graphical toolkit. There are many parameters that the caller |
| 5761 | might like to specify, but which could also be sensibly defaulted, for |
| 5762 | example: |
| 5763 | |
| 5764 | @itemize @bullet |
| 5765 | @item |
| 5766 | color depth -- Default: the color depth for the screen |
| 5767 | |
| 5768 | @item |
| 5769 | background color -- Default: white |
| 5770 | |
| 5771 | @item |
| 5772 | width -- Default: 600 |
| 5773 | |
| 5774 | @item |
| 5775 | height -- Default: 400 |
| 5776 | @end itemize |
| 5777 | |
| 5778 | If @code{make-window} did not use keywords, the caller would have to |
| 5779 | pass in a value for each possible argument, remembering the correct |
| 5780 | argument order and using a special value to indicate the default value |
| 5781 | for that argument: |
| 5782 | |
| 5783 | @lisp |
| 5784 | (make-window 'default ;; Color depth |
| 5785 | 'default ;; Background color |
| 5786 | 800 ;; Width |
| 5787 | 100 ;; Height |
| 5788 | @dots{}) ;; More make-window arguments |
| 5789 | @end lisp |
| 5790 | |
| 5791 | With keywords, on the other hand, defaulted arguments are omitted, and |
| 5792 | non-default arguments are clearly tagged by the appropriate keyword. As |
| 5793 | a result, the invocation becomes much clearer: |
| 5794 | |
| 5795 | @lisp |
| 5796 | (make-window #:width 800 #:height 100) |
| 5797 | @end lisp |
| 5798 | |
| 5799 | On the other hand, for a simpler procedure with few arguments, the use |
| 5800 | of keywords would be a hindrance rather than a help. The primitive |
| 5801 | procedure @code{cons}, for example, would not be improved if it had to |
| 5802 | be invoked as |
| 5803 | |
| 5804 | @lisp |
| 5805 | (cons #:car x #:cdr y) |
| 5806 | @end lisp |
| 5807 | |
| 5808 | So the decision whether to use keywords or not is purely pragmatic: use |
| 5809 | them if they will clarify the procedure invocation at point of call. |
| 5810 | |
| 5811 | @node Coding With Keywords |
| 5812 | @subsubsection Coding With Keywords |
| 5813 | |
| 5814 | If a procedure wants to support keywords, it should take a rest argument |
| 5815 | and then use whatever means is convenient to extract keywords and their |
| 5816 | corresponding arguments from the contents of that rest argument. |
| 5817 | |
| 5818 | The following example illustrates the principle: the code for |
| 5819 | @code{make-window} uses a helper procedure called |
| 5820 | @code{get-keyword-value} to extract individual keyword arguments from |
| 5821 | the rest argument. |
| 5822 | |
| 5823 | @lisp |
| 5824 | (define (get-keyword-value args keyword default) |
| 5825 | (let ((kv (memq keyword args))) |
| 5826 | (if (and kv (>= (length kv) 2)) |
| 5827 | (cadr kv) |
| 5828 | default))) |
| 5829 | |
| 5830 | (define (make-window . args) |
| 5831 | (let ((depth (get-keyword-value args #:depth screen-depth)) |
| 5832 | (bg (get-keyword-value args #:bg "white")) |
| 5833 | (width (get-keyword-value args #:width 800)) |
| 5834 | (height (get-keyword-value args #:height 100)) |
| 5835 | @dots{}) |
| 5836 | @dots{})) |
| 5837 | @end lisp |
| 5838 | |
| 5839 | But you don't need to write @code{get-keyword-value}. The @code{(ice-9 |
| 5840 | optargs)} module provides a set of powerful macros that you can use to |
| 5841 | implement keyword-supporting procedures like this: |
| 5842 | |
| 5843 | @lisp |
| 5844 | (use-modules (ice-9 optargs)) |
| 5845 | |
| 5846 | (define (make-window . args) |
| 5847 | (let-keywords args #f ((depth screen-depth) |
| 5848 | (bg "white") |
| 5849 | (width 800) |
| 5850 | (height 100)) |
| 5851 | ...)) |
| 5852 | @end lisp |
| 5853 | |
| 5854 | @noindent |
| 5855 | Or, even more economically, like this: |
| 5856 | |
| 5857 | @lisp |
| 5858 | (use-modules (ice-9 optargs)) |
| 5859 | |
| 5860 | (define* (make-window #:key (depth screen-depth) |
| 5861 | (bg "white") |
| 5862 | (width 800) |
| 5863 | (height 100)) |
| 5864 | ...) |
| 5865 | @end lisp |
| 5866 | |
| 5867 | For further details on @code{let-keywords}, @code{define*} and other |
| 5868 | facilities provided by the @code{(ice-9 optargs)} module, see |
| 5869 | @ref{Optional Arguments}. |
| 5870 | |
| 5871 | To handle keyword arguments from procedures implemented in C, |
| 5872 | use @code{scm_c_bind_keyword_arguments} (@pxref{Keyword Procedures}). |
| 5873 | |
| 5874 | @node Keyword Read Syntax |
| 5875 | @subsubsection Keyword Read Syntax |
| 5876 | |
| 5877 | Guile, by default, only recognizes a keyword syntax that is compatible |
| 5878 | with R5RS. A token of the form @code{#:NAME}, where @code{NAME} has the |
| 5879 | same syntax as a Scheme symbol (@pxref{Symbol Read Syntax}), is the |
| 5880 | external representation of the keyword named @code{NAME}. Keyword |
| 5881 | objects print using this syntax as well, so values containing keyword |
| 5882 | objects can be read back into Guile. When used in an expression, |
| 5883 | keywords are self-quoting objects. |
| 5884 | |
| 5885 | If the @code{keyword} read option is set to @code{'prefix}, Guile also |
| 5886 | recognizes the alternative read syntax @code{:NAME}. Otherwise, tokens |
| 5887 | of the form @code{:NAME} are read as symbols, as required by R5RS. |
| 5888 | |
| 5889 | @cindex SRFI-88 keyword syntax |
| 5890 | |
| 5891 | If the @code{keyword} read option is set to @code{'postfix}, Guile |
| 5892 | recognizes the SRFI-88 read syntax @code{NAME:} (@pxref{SRFI-88}). |
| 5893 | Otherwise, tokens of this form are read as symbols. |
| 5894 | |
| 5895 | To enable and disable the alternative non-R5RS keyword syntax, you use |
| 5896 | the @code{read-set!} procedure documented @ref{Scheme Read}. Note that |
| 5897 | the @code{prefix} and @code{postfix} syntax are mutually exclusive. |
| 5898 | |
| 5899 | @lisp |
| 5900 | (read-set! keywords 'prefix) |
| 5901 | |
| 5902 | #:type |
| 5903 | @result{} |
| 5904 | #:type |
| 5905 | |
| 5906 | :type |
| 5907 | @result{} |
| 5908 | #:type |
| 5909 | |
| 5910 | (read-set! keywords 'postfix) |
| 5911 | |
| 5912 | type: |
| 5913 | @result{} |
| 5914 | #:type |
| 5915 | |
| 5916 | :type |
| 5917 | @result{} |
| 5918 | :type |
| 5919 | |
| 5920 | (read-set! keywords #f) |
| 5921 | |
| 5922 | #:type |
| 5923 | @result{} |
| 5924 | #:type |
| 5925 | |
| 5926 | :type |
| 5927 | @print{} |
| 5928 | ERROR: In expression :type: |
| 5929 | ERROR: Unbound variable: :type |
| 5930 | ABORT: (unbound-variable) |
| 5931 | @end lisp |
| 5932 | |
| 5933 | @node Keyword Procedures |
| 5934 | @subsubsection Keyword Procedures |
| 5935 | |
| 5936 | @deffn {Scheme Procedure} keyword? obj |
| 5937 | @deffnx {C Function} scm_keyword_p (obj) |
| 5938 | Return @code{#t} if the argument @var{obj} is a keyword, else |
| 5939 | @code{#f}. |
| 5940 | @end deffn |
| 5941 | |
| 5942 | @deffn {Scheme Procedure} keyword->symbol keyword |
| 5943 | @deffnx {C Function} scm_keyword_to_symbol (keyword) |
| 5944 | Return the symbol with the same name as @var{keyword}. |
| 5945 | @end deffn |
| 5946 | |
| 5947 | @deffn {Scheme Procedure} symbol->keyword symbol |
| 5948 | @deffnx {C Function} scm_symbol_to_keyword (symbol) |
| 5949 | Return the keyword with the same name as @var{symbol}. |
| 5950 | @end deffn |
| 5951 | |
| 5952 | @deftypefn {C Function} int scm_is_keyword (SCM obj) |
| 5953 | Equivalent to @code{scm_is_true (scm_keyword_p (@var{obj}))}. |
| 5954 | @end deftypefn |
| 5955 | |
| 5956 | @deftypefn {C Function} SCM scm_from_locale_keyword (const char *name) |
| 5957 | @deftypefnx {C Function} SCM scm_from_locale_keywordn (const char *name, size_t len) |
| 5958 | Equivalent to @code{scm_symbol_to_keyword (scm_from_locale_symbol |
| 5959 | (@var{name}))} and @code{scm_symbol_to_keyword (scm_from_locale_symboln |
| 5960 | (@var{name}, @var{len}))}, respectively. |
| 5961 | |
| 5962 | Note that these functions should @emph{not} be used when @var{name} is a |
| 5963 | C string constant, because there is no guarantee that the current locale |
| 5964 | will match that of the execution character set, used for string and |
| 5965 | character constants. Most modern C compilers use UTF-8 by default, so |
| 5966 | in such cases we recommend @code{scm_from_utf8_keyword}. |
| 5967 | @end deftypefn |
| 5968 | |
| 5969 | @deftypefn {C Function} SCM scm_from_latin1_keyword (const char *name) |
| 5970 | @deftypefnx {C Function} SCM scm_from_utf8_keyword (const char *name) |
| 5971 | Equivalent to @code{scm_symbol_to_keyword (scm_from_latin1_symbol |
| 5972 | (@var{name}))} and @code{scm_symbol_to_keyword (scm_from_utf8_symbol |
| 5973 | (@var{name}))}, respectively. |
| 5974 | @end deftypefn |
| 5975 | |
| 5976 | @deftypefn {C Function} void scm_c_bind_keyword_arguments (const char *subr, @ |
| 5977 | SCM rest, scm_t_keyword_arguments_flags flags, @ |
| 5978 | SCM keyword1, SCM *argp1, @ |
| 5979 | @dots{}, @ |
| 5980 | SCM keywordN, SCM *argpN, @ |
| 5981 | @nicode{SCM_UNDEFINED}) |
| 5982 | |
| 5983 | Extract the specified keyword arguments from @var{rest}, which is not |
| 5984 | modified. If the keyword argument @var{keyword1} is present in |
| 5985 | @var{rest} with an associated value, that value is stored in the |
| 5986 | variable pointed to by @var{argp1}, otherwise the variable is left |
| 5987 | unchanged. Similarly for the other keywords and argument pointers up to |
| 5988 | @var{keywordN} and @var{argpN}. The argument list to |
| 5989 | @code{scm_c_bind_keyword_arguments} must be terminated by |
| 5990 | @code{SCM_UNDEFINED}. |
| 5991 | |
| 5992 | Note that since the variables pointed to by @var{argp1} through |
| 5993 | @var{argpN} are left unchanged if the associated keyword argument is not |
| 5994 | present, they should be initialized to their default values before |
| 5995 | calling @code{scm_c_bind_keyword_arguments}. Alternatively, you can |
| 5996 | initialize them to @code{SCM_UNDEFINED} before the call, and then use |
| 5997 | @code{SCM_UNBNDP} after the call to see which ones were provided. |
| 5998 | |
| 5999 | If an unrecognized keyword argument is present in @var{rest} and |
| 6000 | @var{flags} does not contain @code{SCM_ALLOW_OTHER_KEYS}, or if |
| 6001 | non-keyword arguments are present and @var{flags} does not contain |
| 6002 | @code{SCM_ALLOW_NON_KEYWORD_ARGUMENTS}, an exception is raised. |
| 6003 | @var{subr} should be the name of the procedure receiving the keyword |
| 6004 | arguments, for purposes of error reporting. |
| 6005 | |
| 6006 | For example: |
| 6007 | |
| 6008 | @example |
| 6009 | SCM k_delimiter; |
| 6010 | SCM k_grammar; |
| 6011 | SCM sym_infix; |
| 6012 | |
| 6013 | SCM my_string_join (SCM strings, SCM rest) |
| 6014 | @{ |
| 6015 | SCM delimiter = SCM_UNDEFINED; |
| 6016 | SCM grammar = sym_infix; |
| 6017 | |
| 6018 | scm_c_bind_keyword_arguments ("my-string-join", rest, 0, |
| 6019 | k_delimiter, &delimiter, |
| 6020 | k_grammar, &grammar, |
| 6021 | SCM_UNDEFINED); |
| 6022 | |
| 6023 | if (SCM_UNBNDP (delimiter)) |
| 6024 | delimiter = scm_from_utf8_string (" "); |
| 6025 | |
| 6026 | return scm_string_join (strings, delimiter, grammar); |
| 6027 | @} |
| 6028 | |
| 6029 | void my_init () |
| 6030 | @{ |
| 6031 | k_delimiter = scm_from_utf8_keyword ("delimiter"); |
| 6032 | k_grammar = scm_from_utf8_keyword ("grammar"); |
| 6033 | sym_infix = scm_from_utf8_symbol ("infix"); |
| 6034 | scm_c_define_gsubr ("my-string-join", 1, 0, 1, my_string_join); |
| 6035 | @} |
| 6036 | @end example |
| 6037 | @end deftypefn |
| 6038 | |
| 6039 | |
| 6040 | @node Other Types |
| 6041 | @subsection ``Functionality-Centric'' Data Types |
| 6042 | |
| 6043 | Procedures and macros are documented in their own sections: see |
| 6044 | @ref{Procedures} and @ref{Macros}. |
| 6045 | |
| 6046 | Variable objects are documented as part of the description of Guile's |
| 6047 | module system: see @ref{Variables}. |
| 6048 | |
| 6049 | Asyncs, dynamic roots and fluids are described in the section on |
| 6050 | scheduling: see @ref{Scheduling}. |
| 6051 | |
| 6052 | Hooks are documented in the section on general utility functions: see |
| 6053 | @ref{Hooks}. |
| 6054 | |
| 6055 | Ports are described in the section on I/O: see @ref{Input and Output}. |
| 6056 | |
| 6057 | Regular expressions are described in their own section: see @ref{Regular |
| 6058 | Expressions}. |
| 6059 | |
| 6060 | @c Local Variables: |
| 6061 | @c TeX-master: "guile.texi" |
| 6062 | @c End: |