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1 | @page |
2 | @node Data Types | |
3 | @chapter Data Types for Generic Use | |
4 | ||
5 | This chapter describes all the data types that Guile provides for | |
6 | ``generic use''. | |
7 | ||
8 | One of the great strengths of Scheme is that there is no straightforward | |
9 | distinction between ``data'' and ``functionality''. For example, | |
10 | Guile's support for dynamic linking could be described | |
11 | ||
12 | @itemize | |
13 | @item | |
14 | either in a ``data-centric'' way, as the behaviour and properties of the | |
15 | ``dynamically linked object'' data type, and the operations that may be | |
16 | applied to instances of this type | |
17 | ||
18 | @item | |
19 | or in a ``functionality-centric'' way, as the set of procedures that | |
20 | constitute Guile's support for dynamic linking, in the context of the | |
21 | module system. | |
22 | @end itemize | |
23 | ||
24 | The contents of this chapter are, therefore, a matter of judgement. By | |
25 | ``generic use'', we mean to select those data types whose typical use as | |
26 | @emph{data} in a wide variety of programming contexts is more important | |
27 | than their use in the implementation of a particular piece of | |
28 | @emph{functionality}. | |
29 | ||
30 | @ifinfo | |
31 | The following menu | |
32 | @end ifinfo | |
33 | @iftex | |
34 | The table of contents for this chapter | |
35 | @end iftex | |
36 | @ifhtml | |
37 | The following table of contents | |
38 | @end ifhtml | |
39 | shows the data types that are documented in this chapter. The final | |
40 | section of this chapter lists all the core Guile data types that are not | |
41 | documented here, and provides links to the ``functionality-centric'' | |
42 | sections of this manual that cover them. | |
43 | ||
44 | @menu | |
45 | * Booleans:: True/false values. | |
46 | * Numbers:: Numerical data types. | |
47 | * Characters:: New character names. | |
48 | * Strings:: Special things about strings. | |
49 | * Regular Expressions:: Pattern matching and substitution. | |
50 | * Symbols and Variables:: Manipulating the Scheme symbol table. | |
51 | * Keywords:: Self-quoting, customizable display keywords. | |
52 | * Pairs:: Scheme's basic building block. | |
53 | * Lists:: Special list functions supported by Guile. | |
54 | * Records:: | |
55 | * Structures:: | |
56 | * Arrays:: | |
57 | * Association Lists and Hash Tables:: | |
58 | * Vectors:: | |
59 | * Hooks:: User-customizable event lists. | |
60 | * Other Data Types:: Data types that are documented elsewhere. | |
61 | @end menu | |
62 | ||
63 | ||
64 | @node Booleans | |
65 | @section Booleans | |
fcaedf99 MG |
66 | @r5index not |
67 | @r5index boolean? | |
38a93523 NJ |
68 | |
69 | The two boolean values are @code{#t} for true and @code{#f} for false. | |
70 | ||
71 | Boolean values are returned by predicate procedures, such as the general | |
72 | equality predicates @code{eq?}, @code{eqv?} and @code{equal?} | |
73 | (@pxref{Equality}) and numerical and string comparison operators like | |
74 | @code{string=?} (REFFIXME) and @code{<=} (REFFIXME). | |
75 | ||
76 | @lisp | |
77 | (<= 3 8) | |
78 | @result{} | |
79 | #t | |
80 | ||
81 | (<= 3 -3) | |
82 | @result{} | |
83 | #f | |
84 | ||
85 | (equal? "house" "houses") | |
86 | @result{} | |
87 | #f | |
88 | ||
89 | (eq? #f #f) | |
90 | @result{} | |
91 | #t | |
92 | @end lisp | |
93 | ||
94 | In test condition contexts like @code{if} (REFFIXME) and @code{cond} | |
95 | (REFFIXME), where a group of subexpressions will be evaluated only if a | |
96 | @var{condition} expression evaluates to ``true'', ``true'' means any | |
97 | value at all except @code{#f}. | |
98 | ||
99 | @lisp | |
100 | (if #t "yes" "no") | |
101 | @result{} | |
102 | "yes" | |
103 | ||
104 | (if 0 "yes" "no") | |
105 | @result{} | |
106 | "yes" | |
107 | ||
108 | (if #f "yes" "no") | |
109 | @result{} | |
110 | "no" | |
111 | @end lisp | |
112 | ||
113 | A result of this asymmetry is that typical Scheme source code more often | |
114 | uses @code{#f} explicitly than @code{#t}: @code{#f} is necessary to | |
115 | represent an @code{if} or @code{cond} false value, whereas @code{#t} is | |
116 | not necessary to represent an @code{if} or @code{cond} true value. | |
117 | ||
118 | It is important to note that @code{#f} is @strong{not} equivalent to any | |
119 | other Scheme value. In particular, @code{#f} is not the same as the | |
120 | number 0 (like in C and C++), and not the same as the ``empty list'' | |
121 | (like in some Lisp dialects). | |
122 | ||
123 | The @code{not} procedure returns the boolean inverse of its argument: | |
124 | ||
125 | @c docstring begin (texi-doc-string "guile" "not") | |
126 | @deffn primitive not x | |
127 | Return @code{#t} iff @var{x} is @code{#f}, else return @code{#f}. | |
128 | @end deffn | |
129 | ||
130 | The @code{boolean?} procedure is a predicate that returns @code{#t} if | |
131 | its argument is one of the boolean values, otherwise @code{#f}. | |
132 | ||
133 | @c docstring begin (texi-doc-string "guile" "boolean?") | |
134 | @deffn primitive boolean? obj | |
135 | Return @code{#t} iff @var{obj} is either @code{#t} or @code{#f}. | |
136 | @end deffn | |
137 | ||
138 | ||
139 | @node Numbers | |
140 | @section Numerical data types | |
141 | ||
142 | Guile supports a rich ``tower'' of numerical types --- integer, | |
143 | rational, real and complex --- and provides an extensive set of | |
144 | mathematical and scientific functions for operating on numerical | |
145 | data. This section of the manual documents those types and functions. | |
146 | ||
147 | You may also find it illuminating to read R5RS's presentation of numbers | |
148 | in Scheme, which is particularly clear and accessible: see | |
149 | @xref{Numbers,,,r5rs}. | |
150 | ||
151 | @menu | |
152 | * Numerical Tower:: Scheme's numerical "tower". | |
153 | * Integers:: Whole numbers. | |
154 | * Reals and Rationals:: Real and rational numbers. | |
155 | * Complex Numbers:: Complex numbers. | |
156 | * Exactness:: Exactness and inexactness. | |
157 | * Number Syntax:: Read syntax for numerical data. | |
158 | * Integer Operations:: Operations on integer values. | |
159 | * Comparison:: Comparison predicates. | |
160 | * Conversion:: Converting numbers to and from strings. | |
161 | * Complex:: Complex number operations. | |
162 | * Arithmetic:: Arithmetic functions. | |
163 | * Scientific:: Scientific functions. | |
164 | * Primitive Numerics:: Primitive numeric functions. | |
165 | * Bitwise Operations:: Logical AND, OR, NOT, and so on. | |
166 | * Random:: Random number generation. | |
167 | @end menu | |
168 | ||
169 | ||
170 | @node Numerical Tower | |
171 | @subsection Scheme's Numerical ``Tower'' | |
fcaedf99 | 172 | @r5index number? |
38a93523 NJ |
173 | |
174 | Scheme's numerical ``tower'' consists of the following categories of | |
175 | numbers: | |
176 | ||
177 | @itemize | |
178 | @item | |
179 | integers (whole numbers) | |
180 | ||
181 | @item | |
182 | rationals (the set of numbers that can be expressed as P/Q where P and Q | |
183 | are integers) | |
184 | ||
185 | @item | |
186 | real numbers (the set of numbers that describes all possible positions | |
187 | along a one dimensional line) | |
188 | ||
189 | @item | |
190 | complex numbers (the set of numbers that describes all possible | |
191 | positions in a two dimensional space) | |
192 | @end itemize | |
193 | ||
194 | It is called a tower because each category ``sits on'' the one that | |
195 | follows it, in the sense that every integer is also a rational, every | |
196 | rational is also real, and every real number is also a complex number | |
197 | (but with zero imaginary part). | |
198 | ||
199 | Of these, Guile implements integers, reals and complex numbers as | |
200 | distinct types. Rationals are implemented as regards the read syntax | |
201 | for rational numbers that is specified by R5RS, but are immediately | |
202 | converted by Guile to the corresponding real number. | |
203 | ||
204 | The @code{number?} predicate may be applied to any Scheme value to | |
205 | discover whether the value is any of the supported numerical types. | |
206 | ||
207 | @c docstring begin (texi-doc-string "guile" "number?") | |
208 | @deffn primitive number? obj | |
209 | Return @code{#t} if @var{obj} is any kind of number, @code{#f} else. | |
210 | @end deffn | |
211 | ||
212 | For example: | |
213 | ||
214 | @lisp | |
215 | (number? 3) | |
216 | @result{} | |
217 | #t | |
218 | ||
219 | (number? "hello there!") | |
220 | @result{} | |
221 | #f | |
222 | ||
223 | (define pi 3.141592654) | |
224 | (number? pi) | |
225 | @result{} | |
226 | #t | |
227 | @end lisp | |
228 | ||
229 | The next few subsections document each of Guile's numerical data types | |
230 | in detail. | |
231 | ||
232 | ||
233 | @node Integers | |
234 | @subsection Integers | |
fcaedf99 | 235 | @r5index integer? |
38a93523 NJ |
236 | |
237 | Integers are whole numbers, that is numbers with no fractional part, | |
238 | such as 2, 83 and -3789. | |
239 | ||
240 | Integers in Guile can be arbitrarily big, as shown by the following | |
241 | example. | |
242 | ||
243 | @lisp | |
244 | (define (factorial n) | |
245 | (let loop ((n n) (product 1)) | |
246 | (if (= n 0) | |
247 | product | |
248 | (loop (- n 1) (* product n))))) | |
249 | ||
250 | (factorial 3) | |
251 | @result{} | |
252 | 6 | |
253 | ||
254 | (factorial 20) | |
255 | @result{} | |
256 | 2432902008176640000 | |
257 | ||
258 | (- (factorial 45)) | |
259 | @result{} | |
260 | -119622220865480194561963161495657715064383733760000000000 | |
261 | @end lisp | |
262 | ||
263 | Readers whose background is in programming languages where integers are | |
264 | limited by the need to fit into just 4 or 8 bytes of memory may find | |
265 | this surprising, or suspect that Guile's representation of integers is | |
266 | inefficient. In fact, Guile achieves a near optimal balance of | |
267 | convenience and efficiency by using the host computer's native | |
268 | representation of integers where possible, and a more general | |
269 | representation where the required number does not fit in the native | |
270 | form. Conversion between these two representations is automatic and | |
271 | completely invisible to the Scheme level programmer. | |
272 | ||
273 | @c REFFIXME Maybe point here to discussion of handling immediates/bignums | |
274 | @c on the C level, where the conversion is not so automatic - NJ | |
275 | ||
276 | @c docstring begin (texi-doc-string "guile" "integer?") | |
780ee65e NJ |
277 | @deffn primitive integer? x |
278 | Return @code{#t} if @var{x} is an integer number, @code{#f} else. | |
38a93523 NJ |
279 | |
280 | @lisp | |
281 | (integer? 487) | |
282 | @result{} | |
283 | #t | |
284 | ||
285 | (integer? -3.4) | |
286 | @result{} | |
287 | #f | |
288 | @end lisp | |
289 | @end deffn | |
290 | ||
291 | ||
292 | @node Reals and Rationals | |
293 | @subsection Real and Rational Numbers | |
fcaedf99 MG |
294 | @r5index real? |
295 | @r5index rational? | |
38a93523 NJ |
296 | |
297 | Mathematically, the real numbers are the set of numbers that describe | |
298 | all possible points along a continuous, infinite, one-dimensional line. | |
299 | The rational numbers are the set of all numbers that can be written as | |
300 | fractions P/Q, where P and Q are integers. All rational numbers are | |
301 | also real, but there are real numbers that are not rational, for example | |
302 | the square root of 2, and pi. | |
303 | ||
304 | Guile represents both real and rational numbers approximately using a | |
305 | floating point encoding with limited precision. Even though the actual | |
306 | encoding is in binary, it may be helpful to think of it as a decimal | |
307 | number with a limited number of significant figures and a decimal point | |
308 | somewhere, since this corresponds to the standard notation for non-whole | |
309 | numbers. For example: | |
310 | ||
311 | @lisp | |
312 | 0.34 | |
313 | -0.00000142857931198 | |
314 | -5648394822220000000000.0 | |
315 | 4.0 | |
316 | @end lisp | |
317 | ||
318 | The limited precision of Guile's encoding means that any ``real'' number | |
319 | in Guile can be written in a rational form, by multiplying and then dividing | |
320 | by sufficient powers of 10 (or in fact, 2). For example, | |
321 | @code{-0.00000142857931198} is the same as @code{142857931198} divided by | |
322 | @code{100000000000000000}. In Guile's current incarnation, therefore, | |
323 | the @code{rational?} and @code{real?} predicates are equivalent. | |
324 | ||
325 | Another aspect of this equivalence is that Guile currently does not | |
326 | preserve the exactness that is possible with rational arithmetic. | |
327 | If such exactness is needed, it is of course possible to implement | |
328 | exact rational arithmetic at the Scheme level using Guile's arbitrary | |
329 | size integers. | |
330 | ||
331 | A planned future revision of Guile's numerical tower will make it | |
332 | possible to implement exact representations and arithmetic for both | |
333 | rational numbers and real irrational numbers such as square roots, | |
334 | and in such a way that the new kinds of number integrate seamlessly | |
335 | with those that are already implemented. | |
336 | ||
337 | @c docstring begin (texi-doc-string "guile" "real?") | |
338 | @deffn primitive real? obj | |
339 | Return @code{#t} if @var{obj} is a real number, @code{#f} else. | |
340 | Note that the sets of integer and rational values form subsets | |
341 | of the set of real numbers, so the predicate will also be fulfilled | |
342 | if @var{obj} is an integer number or a rational number. | |
343 | @end deffn | |
344 | ||
345 | @c docstring begin (texi-doc-string "guile" "rational?") | |
780ee65e NJ |
346 | @deffn primitive rational? x |
347 | Return @code{#t} if @var{x} is a rational number, @code{#f} | |
348 | else. Note that the set of integer values forms a subset of | |
349 | the set of rational numbers, i. e. the predicate will also be | |
350 | fulfilled if @var{x} is an integer number. Real numbers | |
351 | will also satisfy this predicate, because of their limited | |
352 | precision. | |
38a93523 NJ |
353 | @end deffn |
354 | ||
355 | ||
356 | @node Complex Numbers | |
357 | @subsection Complex Numbers | |
fcaedf99 | 358 | @r5index complex? |
38a93523 NJ |
359 | |
360 | Complex numbers are the set of numbers that describe all possible points | |
361 | in a two-dimensional space. The two coordinates of a particular point | |
362 | in this space are known as the @dfn{real} and @dfn{imaginary} parts of | |
363 | the complex number that describes that point. | |
364 | ||
365 | In Guile, complex numbers are written in rectangular form as the sum of | |
366 | their real and imaginary parts, using the symbol @code{i} to indicate | |
367 | the imaginary part. | |
368 | ||
369 | @lisp | |
370 | 3+4i | |
371 | @result{} | |
372 | 3.0+4.0i | |
373 | ||
374 | (* 3-8i 2.3+0.3i) | |
375 | @result{} | |
376 | 9.3-17.5i | |
377 | @end lisp | |
378 | ||
379 | Guile represents a complex number as a pair of numbers both of which are | |
380 | real, so the real and imaginary parts of a complex number have the same | |
381 | properties of inexactness and limited precision as single real numbers. | |
382 | ||
383 | @c docstring begin (texi-doc-string "guile" "complex?") | |
780ee65e NJ |
384 | @deffn primitive complex? x |
385 | Return @code{#t} if @var{x} is a complex number, @code{#f} | |
386 | else. Note that the sets of real, rational and integer | |
387 | values form subsets of the set of complex numbers, i. e. the | |
388 | predicate will also be fulfilled if @var{x} is a real, | |
389 | rational or integer number. | |
38a93523 NJ |
390 | @end deffn |
391 | ||
392 | ||
393 | @node Exactness | |
394 | @subsection Exact and Inexact Numbers | |
fcaedf99 MG |
395 | @r5index exact? |
396 | @r5index inexact? | |
397 | @r5index exact->inexact | |
398 | @r5index inexact->exact | |
38a93523 NJ |
399 | |
400 | R5RS requires that a calculation involving inexact numbers always | |
401 | produces an inexact result. To meet this requirement, Guile | |
402 | distinguishes between an exact integer value such as @code{5} and the | |
403 | corresponding inexact real value which, to the limited precision | |
404 | available, has no fractional part, and is printed as @code{5.0}. Guile | |
405 | will only convert the latter value to the former when forced to do so by | |
406 | an invocation of the @code{inexact->exact} procedure. | |
407 | ||
408 | @c docstring begin (texi-doc-string "guile" "exact?") | |
409 | @deffn primitive exact? x | |
780ee65e NJ |
410 | Return @code{#t} if @var{x} is an exact number, @code{#f} |
411 | otherwise. | |
38a93523 NJ |
412 | @end deffn |
413 | ||
414 | @c docstring begin (texi-doc-string "guile" "inexact?") | |
415 | @deffn primitive inexact? x | |
780ee65e NJ |
416 | Return @code{#t} if @var{x} is an inexact number, @code{#f} |
417 | else. | |
38a93523 NJ |
418 | @end deffn |
419 | ||
420 | @c docstring begin (texi-doc-string "guile" "inexact->exact") | |
421 | @deffn primitive inexact->exact z | |
fcaedf99 | 422 | Returns an exact number that is numerically closest to @var{z}. |
38a93523 NJ |
423 | @end deffn |
424 | ||
425 | @c begin (texi-doc-string "guile" "exact->inexact") | |
fcaedf99 MG |
426 | @deffn primitive exact->inexact z |
427 | Convert the number @var{z} to its inexact representation. | |
38a93523 NJ |
428 | @end deffn |
429 | ||
430 | ||
431 | @node Number Syntax | |
432 | @subsection Read Syntax for Numerical Data | |
433 | ||
434 | The read syntax for integers is a string of digits, optionally | |
435 | preceded by a minus or plus character, a code indicating the | |
436 | base in which the integer is encoded, and a code indicating whether | |
437 | the number is exact or inexact. The supported base codes are: | |
438 | ||
439 | @itemize @bullet | |
440 | @item | |
441 | @code{#b}, @code{#B} --- the integer is written in binary (base 2) | |
442 | ||
443 | @item | |
444 | @code{#o}, @code{#O} --- the integer is written in octal (base 8) | |
445 | ||
446 | @item | |
447 | @code{#d}, @code{#D} --- the integer is written in decimal (base 10) | |
448 | ||
449 | @item | |
450 | @code{#x}, @code{#X} --- the integer is written in hexadecimal (base 16). | |
451 | @end itemize | |
452 | ||
453 | If the base code is omitted, the integer is assumed to be decimal. The | |
454 | following examples show how these base codes are used. | |
455 | ||
456 | @lisp | |
457 | -13 | |
458 | @result{} | |
459 | -13 | |
460 | ||
461 | #d-13 | |
462 | @result{} | |
463 | -13 | |
464 | ||
465 | #x-13 | |
466 | @result{} | |
467 | -19 | |
468 | ||
469 | #b+1101 | |
470 | @result{} | |
471 | 13 | |
472 | ||
473 | #o377 | |
474 | @result{} | |
475 | 255 | |
476 | @end lisp | |
477 | ||
478 | The codes for indicating exactness (which can, incidentally, be applied | |
479 | to all numerical values) are: | |
480 | ||
481 | @itemize @bullet | |
482 | @item | |
483 | @code{#e}, @code{#E} --- the number is exact | |
484 | ||
485 | @item | |
486 | @code{#i}, @code{#I} --- the number is inexact. | |
487 | @end itemize | |
488 | ||
489 | If the exactness indicator is omitted, the integer is assumed to be exact, | |
490 | since Guile's internal representation for integers is always exact. | |
491 | Real numbers have limited precision similar to the precision of the | |
492 | @code{double} type in C. A consequence of the limited precision is that | |
493 | all real numbers in Guile are also rational, since any number R with a | |
494 | limited number of decimal places, say N, can be made into an integer by | |
495 | multiplying by 10^N. | |
496 | ||
497 | ||
498 | @node Integer Operations | |
499 | @subsection Operations on Integer Values | |
fcaedf99 MG |
500 | @r5index odd? |
501 | @r5index even? | |
502 | @r5index quotient | |
503 | @r5index remainder | |
504 | @r5index modulo | |
505 | @r5index gcd | |
506 | @r5index lcm | |
38a93523 NJ |
507 | |
508 | @c docstring begin (texi-doc-string "guile" "odd?") | |
509 | @deffn primitive odd? n | |
780ee65e NJ |
510 | Return @code{#t} if @var{n} is an odd number, @code{#f} |
511 | otherwise. | |
38a93523 NJ |
512 | @end deffn |
513 | ||
514 | @c docstring begin (texi-doc-string "guile" "even?") | |
515 | @deffn primitive even? n | |
780ee65e NJ |
516 | Return @code{#t} if @var{n} is an even number, @code{#f} |
517 | otherwise. | |
38a93523 NJ |
518 | @end deffn |
519 | ||
520 | @c begin (texi-doc-string "guile" "quotient") | |
521 | @deffn primitive quotient | |
fcaedf99 | 522 | Return the quotient of the numbers @var{x} and @var{y}. |
38a93523 NJ |
523 | @end deffn |
524 | ||
525 | @c begin (texi-doc-string "guile" "remainder") | |
526 | @deffn primitive remainder | |
fcaedf99 MG |
527 | Return the remainder of the numbers @var{x} and @var{y}. |
528 | @lisp | |
529 | (remainder 13 4) @result{} 1 | |
530 | (remainder -13 4) @result{} -1 | |
531 | @end lisp | |
38a93523 NJ |
532 | @end deffn |
533 | ||
534 | @c begin (texi-doc-string "guile" "modulo") | |
535 | @deffn primitive modulo | |
fcaedf99 MG |
536 | Return the modulo of the numbers @var{x} and @var{y}. |
537 | @lisp | |
538 | (modulo 13 4) @result{} 1 | |
539 | (modulo -13 4) @result{} 3 | |
540 | @end lisp | |
38a93523 NJ |
541 | @end deffn |
542 | ||
543 | @c begin (texi-doc-string "guile" "gcd") | |
544 | @deffn primitive gcd | |
fcaedf99 MG |
545 | Return the greatest common divisor of all arguments. |
546 | If called without arguments, 0 is returned. | |
38a93523 NJ |
547 | @end deffn |
548 | ||
549 | @c begin (texi-doc-string "guile" "lcm") | |
550 | @deffn primitive lcm | |
fcaedf99 MG |
551 | Return the least common multiple of the arguments. |
552 | If called without arguments, 1 is returned. | |
38a93523 NJ |
553 | @end deffn |
554 | ||
555 | ||
556 | @node Comparison | |
557 | @subsection Comparison Predicates | |
fcaedf99 MG |
558 | @r5index zero? |
559 | @r5index positive? | |
560 | @r5index negative? | |
38a93523 NJ |
561 | |
562 | @c begin (texi-doc-string "guile" "=") | |
563 | @deffn primitive = | |
fcaedf99 | 564 | Return @code{#t} if all parameters are numerically equal. |
38a93523 NJ |
565 | @end deffn |
566 | ||
567 | @c begin (texi-doc-string "guile" "<") | |
568 | @deffn primitive < | |
fcaedf99 MG |
569 | Return @code{#t} if the list of parameters is monotonically |
570 | increasing. | |
38a93523 NJ |
571 | @end deffn |
572 | ||
573 | @c begin (texi-doc-string "guile" ">") | |
574 | @deffn primitive > | |
fcaedf99 MG |
575 | Return @code{#t} if the list of parameters is monotonically |
576 | decreasing. | |
38a93523 NJ |
577 | @end deffn |
578 | ||
579 | @c begin (texi-doc-string "guile" "<=") | |
580 | @deffn primitive <= | |
fcaedf99 MG |
581 | Return @code{#t} if the list of parameters is monotonically |
582 | non-decreasing. | |
38a93523 NJ |
583 | @end deffn |
584 | ||
585 | @c begin (texi-doc-string "guile" ">=") | |
586 | @deffn primitive >= | |
fcaedf99 MG |
587 | Return @code{#t} if the list of parameters is monotonically |
588 | non-increasing. | |
38a93523 NJ |
589 | @end deffn |
590 | ||
591 | @c begin (texi-doc-string "guile" "zero?") | |
592 | @deffn primitive zero? | |
fcaedf99 MG |
593 | Return @code{#t} if @var{z} is an exact or inexact number equal to |
594 | zero. | |
38a93523 NJ |
595 | @end deffn |
596 | ||
597 | @c begin (texi-doc-string "guile" "positive?") | |
598 | @deffn primitive positive? | |
fcaedf99 MG |
599 | Return @code{#t} if @var{x} is an exact or inexact number greater than |
600 | zero. | |
38a93523 NJ |
601 | @end deffn |
602 | ||
603 | @c begin (texi-doc-string "guile" "negative?") | |
604 | @deffn primitive negative? | |
fcaedf99 MG |
605 | Return @code{#t} if @var{x} is an exact or inexact number less than |
606 | zero. | |
38a93523 NJ |
607 | @end deffn |
608 | ||
609 | ||
610 | @node Conversion | |
611 | @subsection Converting Numbers To and From Strings | |
fcaedf99 MG |
612 | @r5index number->string |
613 | @r5index string->number | |
38a93523 NJ |
614 | |
615 | @c docstring begin (texi-doc-string "guile" "number->string") | |
616 | @deffn primitive number->string n [radix] | |
617 | Return a string holding the external representation of the | |
780ee65e NJ |
618 | number @var{n} in the given @var{radix}. If @var{n} is |
619 | inexact, a radix of 10 will be used. | |
38a93523 NJ |
620 | @end deffn |
621 | ||
622 | @c docstring begin (texi-doc-string "guile" "string->number") | |
623 | @deffn primitive string->number string [radix] | |
624 | Returns a number of the maximally precise representation | |
780ee65e NJ |
625 | expressed by the given @var{string}. @var{radix} must be an |
626 | exact integer, either 2, 8, 10, or 16. If supplied, @var{radix} | |
627 | is a default radix that may be overridden by an explicit radix | |
628 | prefix in @var{string} (e.g. "#o177"). If @var{radix} is not | |
629 | supplied, then the default radix is 10. If string is not a | |
630 | syntactically valid notation for a number, then | |
631 | @code{string->number} returns @code{#f}. | |
38a93523 NJ |
632 | @end deffn |
633 | ||
634 | ||
635 | @node Complex | |
636 | @subsection Complex Number Operations | |
fcaedf99 MG |
637 | @r5index make-rectangular |
638 | @r5index make-polar | |
639 | @r5index real-part | |
640 | @r5index imag-part | |
641 | @r5index magnitude | |
642 | @r5index angle | |
38a93523 NJ |
643 | |
644 | @c docstring begin (texi-doc-string "guile" "make-rectangular") | |
645 | @deffn primitive make-rectangular real imaginary | |
780ee65e NJ |
646 | Return a complex number constructed of the given @var{real} and |
647 | @var{imaginary} parts. | |
38a93523 NJ |
648 | @end deffn |
649 | ||
650 | @c docstring begin (texi-doc-string "guile" "make-polar") | |
651 | @deffn primitive make-polar x y | |
780ee65e | 652 | Return the complex number @var{x} * e^(i * @var{y}). |
38a93523 NJ |
653 | @end deffn |
654 | ||
655 | @c begin (texi-doc-string "guile" "real-part") | |
656 | @deffn primitive real-part | |
fcaedf99 | 657 | Return the real part of the number @var{z}. |
38a93523 NJ |
658 | @end deffn |
659 | ||
660 | @c begin (texi-doc-string "guile" "imag-part") | |
661 | @deffn primitive imag-part | |
fcaedf99 | 662 | Return the imaginary part of the number @var{z}. |
38a93523 NJ |
663 | @end deffn |
664 | ||
665 | @c begin (texi-doc-string "guile" "magnitude") | |
666 | @deffn primitive magnitude | |
fcaedf99 MG |
667 | Return the magnitude of the number @var{z}. This is the same as |
668 | @code{abs} for real arguments, but also allows complex numbers. | |
38a93523 NJ |
669 | @end deffn |
670 | ||
671 | @c begin (texi-doc-string "guile" "angle") | |
672 | @deffn primitive angle | |
fcaedf99 | 673 | Return the angle of the complex number @var{z}. |
38a93523 NJ |
674 | @end deffn |
675 | ||
676 | ||
677 | @node Arithmetic | |
678 | @subsection Arithmetic Functions | |
fcaedf99 MG |
679 | @r5index max |
680 | @r5index min | |
681 | @r5index + | |
682 | @r5index * | |
683 | @r5index - | |
684 | @r5index / | |
685 | @r5index abs | |
686 | @r5index floor | |
687 | @r5index ceiling | |
688 | @r5index truncate | |
689 | @r5index round | |
38a93523 NJ |
690 | |
691 | @c begin (texi-doc-string "guile" "+") | |
fcaedf99 MG |
692 | @deffn primitive + z1 @dots{} |
693 | Return the sum of all parameter values. Return 0 if called without any | |
694 | parameters. | |
38a93523 NJ |
695 | @end deffn |
696 | ||
697 | @c begin (texi-doc-string "guile" "-") | |
fcaedf99 MG |
698 | @deffn primitive - z1 z2 @dots{} |
699 | If called without arguments, 0 is returned. Otherwise the sum of all but | |
700 | the first argument are subtracted from the first argument. | |
38a93523 NJ |
701 | @end deffn |
702 | ||
703 | @c begin (texi-doc-string "guile" "*") | |
fcaedf99 MG |
704 | @deffn primitive * z1 @dots{} |
705 | Return the product of all arguments. If called without arguments, 1 is | |
706 | returned. | |
38a93523 NJ |
707 | @end deffn |
708 | ||
709 | @c begin (texi-doc-string "guile" "/") | |
fcaedf99 MG |
710 | @deffn primitive / z1 z2 @dots{} |
711 | Divide the first argument by the product of the remaining arguments. | |
38a93523 NJ |
712 | @end deffn |
713 | ||
714 | @c begin (texi-doc-string "guile" "abs") | |
fcaedf99 MG |
715 | @deffn primitive abs x |
716 | Return the absolute value of @var{x}. | |
38a93523 NJ |
717 | @end deffn |
718 | ||
719 | @c begin (texi-doc-string "guile" "max") | |
fcaedf99 MG |
720 | @deffn primitive max x1 x2 @dots{} |
721 | Return the maximum of all parameter values. | |
38a93523 NJ |
722 | @end deffn |
723 | ||
724 | @c begin (texi-doc-string "guile" "min") | |
fcaedf99 MG |
725 | @deffn primitive min x1 x2 @dots{} |
726 | Return the minium of all parameter values. | |
38a93523 NJ |
727 | @end deffn |
728 | ||
729 | @c begin (texi-doc-string "guile" "truncate") | |
730 | @deffn primitive truncate | |
fcaedf99 | 731 | Round the inexact number @var{x} towards zero. |
38a93523 NJ |
732 | @end deffn |
733 | ||
734 | @c begin (texi-doc-string "guile" "round") | |
fcaedf99 MG |
735 | @deffn primitive round x |
736 | Round the inexact number @var{x} towards zero. | |
38a93523 NJ |
737 | @end deffn |
738 | ||
739 | @c begin (texi-doc-string "guile" "floor") | |
fcaedf99 MG |
740 | @deffn primitive floor x |
741 | Round the number @var{x} towards minus infinity. | |
38a93523 NJ |
742 | @end deffn |
743 | ||
744 | @c begin (texi-doc-string "guile" "ceiling") | |
fcaedf99 MG |
745 | @deffn primitive ceiling x |
746 | Round the number @var{x} towards infinity. | |
38a93523 NJ |
747 | @end deffn |
748 | ||
749 | ||
750 | @node Scientific | |
751 | @subsection Scientific Functions | |
fcaedf99 MG |
752 | @r5index exp |
753 | @r5index log | |
754 | @r5index sin | |
755 | @r5index cos | |
756 | @r5index tan | |
757 | @r5index asin | |
758 | @r5index acos | |
759 | @r5index atan | |
760 | @r5index sqrt | |
761 | @r5index expt | |
38a93523 NJ |
762 | |
763 | The following procedures accept any kind of number as arguments, | |
764 | including complex numbers. | |
765 | ||
766 | @c begin (texi-doc-string "guile" "sqrt") | |
767 | @deffn procedure sqrt z | |
768 | Return the square root of @var{z}. | |
769 | @end deffn | |
770 | ||
771 | @c begin (texi-doc-string "guile" "expt") | |
772 | @deffn procedure expt z1 z2 | |
773 | Return @var{z1} raised to the power of @var{z2}. | |
774 | @end deffn | |
775 | ||
776 | @c begin (texi-doc-string "guile" "sin") | |
777 | @deffn procedure sin z | |
778 | Return the sine of @var{z}. | |
779 | @end deffn | |
780 | ||
781 | @c begin (texi-doc-string "guile" "cos") | |
782 | @deffn procedure cos z | |
783 | Return the cosine of @var{z}. | |
784 | @end deffn | |
785 | ||
786 | @c begin (texi-doc-string "guile" "tan") | |
787 | @deffn procedure tan z | |
788 | Return the tangent of @var{z}. | |
789 | @end deffn | |
790 | ||
791 | @c begin (texi-doc-string "guile" "asin") | |
792 | @deffn procedure asin z | |
793 | Return the arcsine of @var{z}. | |
794 | @end deffn | |
795 | ||
796 | @c begin (texi-doc-string "guile" "acos") | |
797 | @deffn procedure acos z | |
798 | Return the arccosine of @var{z}. | |
799 | @end deffn | |
800 | ||
801 | @c begin (texi-doc-string "guile" "atan") | |
802 | @deffn procedure atan z | |
803 | Return the arctangent of @var{z}. | |
804 | @end deffn | |
805 | ||
806 | @c begin (texi-doc-string "guile" "exp") | |
807 | @deffn procedure exp z | |
808 | Return e to the power of @var{z}, where e is the base of natural | |
809 | logarithms (2.71828@dots{}). | |
810 | @end deffn | |
811 | ||
812 | @c begin (texi-doc-string "guile" "log") | |
813 | @deffn procedure log z | |
814 | Return the natural logarithm of @var{z}. | |
815 | @end deffn | |
816 | ||
817 | @c begin (texi-doc-string "guile" "log10") | |
818 | @deffn procedure log10 z | |
819 | Return the base 10 logarithm of @var{z}. | |
820 | @end deffn | |
821 | ||
822 | @c begin (texi-doc-string "guile" "sinh") | |
823 | @deffn procedure sinh z | |
824 | Return the hyperbolic sine of @var{z}. | |
825 | @end deffn | |
826 | ||
827 | @c begin (texi-doc-string "guile" "cosh") | |
828 | @deffn procedure cosh z | |
829 | Return the hyperbolic cosine of @var{z}. | |
830 | @end deffn | |
831 | ||
832 | @c begin (texi-doc-string "guile" "tanh") | |
833 | @deffn procedure tanh z | |
834 | Return the hyperbolic tangent of @var{z}. | |
835 | @end deffn | |
836 | ||
837 | @c begin (texi-doc-string "guile" "asinh") | |
838 | @deffn procedure asinh z | |
839 | Return the hyperbolic arcsine of @var{z}. | |
840 | @end deffn | |
841 | ||
842 | @c begin (texi-doc-string "guile" "acosh") | |
843 | @deffn procedure acosh z | |
844 | Return the hyperbolic arccosine of @var{z}. | |
845 | @end deffn | |
846 | ||
847 | @c begin (texi-doc-string "guile" "atanh") | |
848 | @deffn procedure atanh z | |
849 | Return the hyperbolic arctangent of @var{z}. | |
850 | @end deffn | |
851 | ||
852 | ||
853 | @node Primitive Numerics | |
854 | @subsection Primitive Numeric Functions | |
855 | ||
856 | Many of Guile's numeric procedures which accept any kind of numbers as | |
857 | arguments, including complex numbers, are implemented as Scheme | |
858 | procedures that use the following real number-based primitives. These | |
859 | primitives signal an error if they are called with complex arguments. | |
860 | ||
861 | @c begin (texi-doc-string "guile" "$abs") | |
862 | @deffn primitive $abs x | |
863 | Return the absolute value of @var{x}. | |
864 | @end deffn | |
865 | ||
866 | @c begin (texi-doc-string "guile" "$sqrt") | |
867 | @deffn primitive $sqrt x | |
868 | Return the square root of @var{x}. | |
869 | @end deffn | |
870 | ||
871 | @c docstring begin (texi-doc-string "guile" "$expt") | |
872 | @deffn primitive $expt x y | |
873 | Return @var{x} raised to the power of @var{y}. This | |
874 | procedure does not accept complex arguments. | |
875 | @end deffn | |
876 | ||
877 | @c begin (texi-doc-string "guile" "$sin") | |
878 | @deffn primitive $sin x | |
879 | Return the sine of @var{x}. | |
880 | @end deffn | |
881 | ||
882 | @c begin (texi-doc-string "guile" "$cos") | |
883 | @deffn primitive $cos x | |
884 | Return the cosine of @var{x}. | |
885 | @end deffn | |
886 | ||
887 | @c begin (texi-doc-string "guile" "$tan") | |
888 | @deffn primitive $tan x | |
889 | Return the tangent of @var{x}. | |
890 | @end deffn | |
891 | ||
892 | @c begin (texi-doc-string "guile" "$asin") | |
893 | @deffn primitive $asin x | |
894 | Return the arcsine of @var{x}. | |
895 | @end deffn | |
896 | ||
897 | @c begin (texi-doc-string "guile" "$acos") | |
898 | @deffn primitive $acos x | |
899 | Return the arccosine of @var{x}. | |
900 | @end deffn | |
901 | ||
902 | @c begin (texi-doc-string "guile" "$atan") | |
903 | @deffn primitive $atan x | |
904 | Return the arctangent of @var{x} in the range -PI/2 to PI/2. | |
905 | @end deffn | |
906 | ||
907 | @c docstring begin (texi-doc-string "guile" "$atan2") | |
908 | @deffn primitive $atan2 x y | |
909 | Return the arc tangent of the two arguments @var{x} and | |
910 | @var{y}. This is similar to calculating the arc tangent of | |
911 | @var{x} / @var{y}, except that the signs of both arguments | |
912 | are used to determine the quadrant of the result. This | |
913 | procedure does not accept complex arguments. | |
914 | @end deffn | |
915 | ||
916 | @c begin (texi-doc-string "guile" "$exp") | |
917 | @deffn primitive $exp x | |
918 | Return e to the power of @var{x}, where e is the base of natural | |
919 | logarithms (2.71828@dots{}). | |
920 | @end deffn | |
921 | ||
922 | @c begin (texi-doc-string "guile" "$log") | |
923 | @deffn primitive $log x | |
924 | Return the natural logarithm of @var{x}. | |
925 | @end deffn | |
926 | ||
927 | @c begin (texi-doc-string "guile" "$sinh") | |
928 | @deffn primitive $sinh x | |
929 | Return the hyperbolic sine of @var{x}. | |
930 | @end deffn | |
931 | ||
932 | @c begin (texi-doc-string "guile" "$cosh") | |
933 | @deffn primitive $cosh x | |
934 | Return the hyperbolic cosine of @var{x}. | |
935 | @end deffn | |
936 | ||
937 | @c begin (texi-doc-string "guile" "$tanh") | |
938 | @deffn primitive $tanh x | |
939 | Return the hyperbolic tangent of @var{x}. | |
940 | @end deffn | |
941 | ||
942 | @c begin (texi-doc-string "guile" "$asinh") | |
943 | @deffn primitive $asinh x | |
944 | Return the hyperbolic arcsine of @var{x}. | |
945 | @end deffn | |
946 | ||
947 | @c begin (texi-doc-string "guile" "$acosh") | |
948 | @deffn primitive $acosh x | |
949 | Return the hyperbolic arccosine of @var{x}. | |
950 | @end deffn | |
951 | ||
952 | @c begin (texi-doc-string "guile" "$atanh") | |
953 | @deffn primitive $atanh x | |
954 | Return the hyperbolic arctangent of @var{x}. | |
955 | @end deffn | |
956 | ||
957 | ||
958 | @node Bitwise Operations | |
959 | @subsection Bitwise Operations | |
960 | ||
961 | @c docstring begin (texi-doc-string "guile" "logand") | |
962 | @deffn primitive logand n1 n2 | |
963 | Returns the integer which is the bit-wise AND of the two integer | |
964 | arguments. | |
965 | ||
966 | Example: | |
967 | @lisp | |
968 | (number->string (logand #b1100 #b1010) 2) | |
969 | @result{} "1000" | |
970 | @end lisp | |
971 | @end deffn | |
972 | ||
973 | @c docstring begin (texi-doc-string "guile" "logior") | |
974 | @deffn primitive logior n1 n2 | |
975 | Returns the integer which is the bit-wise OR of the two integer | |
976 | arguments. | |
977 | ||
978 | Example: | |
979 | @lisp | |
980 | (number->string (logior #b1100 #b1010) 2) | |
981 | @result{} "1110" | |
982 | @end lisp | |
983 | @end deffn | |
984 | ||
985 | @c docstring begin (texi-doc-string "guile" "logxor") | |
986 | @deffn primitive logxor n1 n2 | |
987 | Returns the integer which is the bit-wise XOR of the two integer | |
988 | arguments. | |
989 | ||
990 | Example: | |
991 | @lisp | |
992 | (number->string (logxor #b1100 #b1010) 2) | |
993 | @result{} "110" | |
994 | @end lisp | |
995 | @end deffn | |
996 | ||
997 | @c docstring begin (texi-doc-string "guile" "lognot") | |
998 | @deffn primitive lognot n | |
999 | Returns the integer which is the 2s-complement of the integer argument. | |
1000 | ||
1001 | Example: | |
1002 | @lisp | |
1003 | (number->string (lognot #b10000000) 2) | |
1004 | @result{} "-10000001" | |
1005 | (number->string (lognot #b0) 2) | |
1006 | @result{} "-1" | |
1007 | @end lisp | |
1008 | @end deffn | |
1009 | ||
1010 | @c ARGFIXME j/n1 k/n2 | |
1011 | @c docstring begin (texi-doc-string "guile" "logtest") | |
1012 | @deffn primitive logtest n1 n2 | |
1013 | @example | |
1014 | (logtest j k) @equiv{} (not (zero? (logand j k))) | |
1015 | ||
1016 | (logtest #b0100 #b1011) @result{} #f | |
1017 | (logtest #b0100 #b0111) @result{} #t | |
1018 | @end example | |
1019 | @end deffn | |
1020 | ||
1021 | @c docstring begin (texi-doc-string "guile" "logbit?") | |
1022 | @deffn primitive logbit? index j | |
1023 | @example | |
1024 | (logbit? index j) @equiv{} (logtest (integer-expt 2 index) j) | |
1025 | ||
1026 | (logbit? 0 #b1101) @result{} #t | |
1027 | (logbit? 1 #b1101) @result{} #f | |
1028 | (logbit? 2 #b1101) @result{} #t | |
1029 | (logbit? 3 #b1101) @result{} #t | |
1030 | (logbit? 4 #b1101) @result{} #f | |
1031 | @end example | |
1032 | @end deffn | |
1033 | ||
1034 | @c ARGFIXME n/int cnt/count | |
1035 | @c docstring begin (texi-doc-string "guile" "ash") | |
1036 | @deffn primitive ash n cnt | |
780ee65e NJ |
1037 | The function ash performs an arithmetic shift left by @var{CNT} |
1038 | bits (or shift right, if @var{cnt} is negative). | |
1039 | 'Arithmetic' means, that the function does not guarantee to | |
1040 | keep the bit structure of @var{n}, but rather guarantees that | |
1041 | the result will always be rounded towards minus infinity. | |
1042 | Therefore, the results of ash and a corresponding bitwise | |
1043 | shift will differ if N is negative. | |
38a93523 NJ |
1044 | |
1045 | Formally, the function returns an integer equivalent to | |
780ee65e | 1046 | @code{(inexact->exact (floor (* @var{n} (expt 2 @var{cnt}))))}. |
38a93523 NJ |
1047 | |
1048 | Example: | |
1049 | @lisp | |
1050 | (number->string (ash #b1 3) 2) | |
1051 | @result{} "1000" | |
1052 | (number->string (ash #b1010 -1) 2) | |
1053 | @result{} "101" | |
1054 | @end lisp | |
1055 | @end deffn | |
1056 | ||
1057 | @c docstring begin (texi-doc-string "guile" "logcount") | |
1058 | @deffn primitive logcount n | |
1059 | Returns the number of bits in integer @var{n}. If integer is positive, | |
1060 | the 1-bits in its binary representation are counted. If negative, the | |
1061 | 0-bits in its two's-complement binary representation are counted. If 0, | |
1062 | 0 is returned. | |
1063 | ||
1064 | Example: | |
1065 | @lisp | |
1066 | (logcount #b10101010) | |
1067 | @result{} 4 | |
1068 | (logcount 0) | |
1069 | @result{} 0 | |
1070 | (logcount -2) | |
1071 | @result{} 1 | |
1072 | @end lisp | |
1073 | @end deffn | |
1074 | ||
1075 | @c docstring begin (texi-doc-string "guile" "integer-length") | |
1076 | @deffn primitive integer-length n | |
1077 | Returns the number of bits neccessary to represent @var{n}. | |
1078 | ||
1079 | Example: | |
1080 | @lisp | |
1081 | (integer-length #b10101010) | |
1082 | @result{} 8 | |
1083 | (integer-length 0) | |
1084 | @result{} 0 | |
1085 | (integer-length #b1111) | |
1086 | @result{} 4 | |
1087 | @end lisp | |
1088 | @end deffn | |
1089 | ||
1090 | @c docstring begin (texi-doc-string "guile" "integer-expt") | |
1091 | @deffn primitive integer-expt n k | |
1092 | Returns @var{n} raised to the non-negative integer exponent @var{k}. | |
1093 | ||
1094 | Example: | |
1095 | @lisp | |
1096 | (integer-expt 2 5) | |
1097 | @result{} 32 | |
1098 | (integer-expt -3 3) | |
1099 | @result{} -27 | |
1100 | @end lisp | |
1101 | @end deffn | |
1102 | ||
1103 | @c docstring begin (texi-doc-string "guile" "bit-extract") | |
1104 | @deffn primitive bit-extract n start end | |
1105 | Returns the integer composed of the @var{start} (inclusive) through | |
1106 | @var{end} (exclusive) bits of @var{n}. The @var{start}th bit becomes | |
1107 | the 0-th bit in the result.@refill | |
1108 | ||
1109 | Example: | |
1110 | @lisp | |
1111 | (number->string (bit-extract #b1101101010 0 4) 2) | |
1112 | @result{} "1010" | |
1113 | (number->string (bit-extract #b1101101010 4 9) 2) | |
1114 | @result{} "10110" | |
1115 | @end lisp | |
1116 | @end deffn | |
1117 | ||
1118 | ||
1119 | @node Random | |
1120 | @subsection Random Number Generation | |
1121 | ||
1122 | @c docstring begin (texi-doc-string "guile" "copy-random-state") | |
1123 | @deffn primitive copy-random-state [state] | |
1124 | Return a copy of the random state @var{state}. | |
1125 | @end deffn | |
1126 | ||
1127 | @c docstring begin (texi-doc-string "guile" "random") | |
1128 | @deffn primitive random n [state] | |
1129 | Return a number in [0,N). | |
1130 | Accepts a positive integer or real n and returns a | |
1131 | number of the same type between zero (inclusive) and | |
1132 | N (exclusive). The values returned have a uniform | |
1133 | distribution. | |
1134 | The optional argument @var{state} must be of the type produced | |
1135 | by @code{seed->random-state}. It defaults to the value of the | |
1136 | variable @var{*random-state*}. This object is used to maintain | |
1137 | the state of the pseudo-random-number generator and is altered | |
1138 | as a side effect of the random operation. | |
1139 | @end deffn | |
1140 | ||
1141 | @c docstring begin (texi-doc-string "guile" "random:exp") | |
1142 | @deffn primitive random:exp [state] | |
1143 | Returns an inexact real in an exponential distribution with mean 1. | |
1144 | For an exponential distribution with mean u use (* u (random:exp)). | |
1145 | @end deffn | |
1146 | ||
1147 | @c docstring begin (texi-doc-string "guile" "random:hollow-sphere!") | |
1148 | @deffn primitive random:hollow-sphere! v [state] | |
1149 | Fills vect with inexact real random numbers | |
1150 | the sum of whose squares is equal to 1.0. | |
1151 | Thinking of vect as coordinates in space of | |
1152 | dimension n = (vector-length vect), the coordinates | |
1153 | are uniformly distributed over the surface of the | |
1154 | unit n-shere. | |
1155 | @end deffn | |
1156 | ||
1157 | @c docstring begin (texi-doc-string "guile" "random:normal") | |
1158 | @deffn primitive random:normal [state] | |
1159 | Returns an inexact real in a normal distribution. | |
1160 | The distribution used has mean 0 and standard deviation 1. | |
1161 | For a normal distribution with mean m and standard deviation | |
1162 | d use @code{(+ m (* d (random:normal)))}. | |
1163 | @end deffn | |
1164 | ||
1165 | @c docstring begin (texi-doc-string "guile" "random:normal-vector!") | |
1166 | @deffn primitive random:normal-vector! v [state] | |
1167 | Fills vect with inexact real random numbers that are | |
1168 | independent and standard normally distributed | |
1169 | (i.e., with mean 0 and variance 1). | |
1170 | @end deffn | |
1171 | ||
1172 | @c docstring begin (texi-doc-string "guile" "random:solid-sphere!") | |
1173 | @deffn primitive random:solid-sphere! v [state] | |
1174 | Fills vect with inexact real random numbers | |
1175 | the sum of whose squares is less than 1.0. | |
1176 | Thinking of vect as coordinates in space of | |
1177 | dimension n = (vector-length vect), the coordinates | |
1178 | are uniformly distributed within the unit n-shere. | |
1179 | The sum of the squares of the numbers is returned. | |
1180 | @end deffn | |
1181 | ||
1182 | @c docstring begin (texi-doc-string "guile" "random:uniform") | |
1183 | @deffn primitive random:uniform [state] | |
1184 | Returns a uniformly distributed inexact real random number in [0,1). | |
1185 | @end deffn | |
1186 | ||
1187 | @c docstring begin (texi-doc-string "guile" "seed->random-state") | |
1188 | @deffn primitive seed->random-state seed | |
1189 | Return a new random state using @var{seed}. | |
1190 | @end deffn | |
1191 | ||
1192 | ||
1193 | @node Characters | |
1194 | @section Characters | |
fcaedf99 MG |
1195 | @r5index char? |
1196 | @r5index char=? | |
1197 | @r5index char<? | |
1198 | @r5index char>? | |
1199 | @r5index char<=? | |
1200 | @r5index char>=? | |
1201 | @r5index char-alphabetic? | |
1202 | @r5index char-numeric? | |
1203 | @r5index char-whitespace? | |
1204 | @r5index char-upper-case? | |
1205 | @r5index char-lower-case? | |
1206 | @r5index char->integer | |
1207 | @r5index integer->char | |
1208 | @r5index char-upcase | |
1209 | @r5index char-downcase | |
1210 | ||
38a93523 NJ |
1211 | |
1212 | Most of the characters in the ASCII character set may be referred to by | |
1213 | name: for example, @code{#\tab}, @code{#\esc}, @code{#\stx}, and so on. | |
1214 | The following table describes the ASCII names for each character. | |
1215 | ||
1216 | @multitable @columnfractions .25 .25 .25 .25 | |
1217 | @item 0 = @code{#\nul} | |
1218 | @tab 1 = @code{#\soh} | |
1219 | @tab 2 = @code{#\stx} | |
1220 | @tab 3 = @code{#\etx} | |
1221 | @item 4 = @code{#\eot} | |
1222 | @tab 5 = @code{#\enq} | |
1223 | @tab 6 = @code{#\ack} | |
1224 | @tab 7 = @code{#\bel} | |
1225 | @item 8 = @code{#\bs} | |
1226 | @tab 9 = @code{#\ht} | |
1227 | @tab 10 = @code{#\nl} | |
1228 | @tab 11 = @code{#\vt} | |
1229 | @item 12 = @code{#\np} | |
1230 | @tab 13 = @code{#\cr} | |
1231 | @tab 14 = @code{#\so} | |
1232 | @tab 15 = @code{#\si} | |
1233 | @item 16 = @code{#\dle} | |
1234 | @tab 17 = @code{#\dc1} | |
1235 | @tab 18 = @code{#\dc2} | |
1236 | @tab 19 = @code{#\dc3} | |
1237 | @item 20 = @code{#\dc4} | |
1238 | @tab 21 = @code{#\nak} | |
1239 | @tab 22 = @code{#\syn} | |
1240 | @tab 23 = @code{#\etb} | |
1241 | @item 24 = @code{#\can} | |
1242 | @tab 25 = @code{#\em} | |
1243 | @tab 26 = @code{#\sub} | |
1244 | @tab 27 = @code{#\esc} | |
1245 | @item 28 = @code{#\fs} | |
1246 | @tab 29 = @code{#\gs} | |
1247 | @tab 30 = @code{#\rs} | |
1248 | @tab 31 = @code{#\us} | |
1249 | @item 32 = @code{#\sp} | |
1250 | @end multitable | |
1251 | ||
1252 | The @code{delete} character (octal 177) may be referred to with the name | |
1253 | @code{#\del}. | |
1254 | ||
1255 | Several characters have more than one name: | |
1256 | ||
1257 | @itemize @bullet | |
1258 | @item | |
1259 | #\space, #\sp | |
1260 | @item | |
1261 | #\newline, #\nl | |
1262 | @item | |
1263 | #\tab, #\ht | |
1264 | @item | |
1265 | #\backspace, #\bs | |
1266 | @item | |
1267 | #\return, #\cr | |
1268 | @item | |
1269 | #\page, #\np | |
1270 | @item | |
1271 | #\null, #\nul | |
1272 | @end itemize | |
1273 | ||
1274 | @c docstring begin (texi-doc-string "guile" "char?") | |
1275 | @deffn primitive char? x | |
1276 | Return @code{#t} iff @var{x} is a character, else @code{#f}. | |
1277 | @end deffn | |
1278 | ||
1279 | @c docstring begin (texi-doc-string "guile" "char=?") | |
1280 | @deffn primitive char=? x y | |
1281 | Return @code{#t} iff @var{x} is the same character as @var{y}, else @code{#f}. | |
1282 | @end deffn | |
1283 | ||
1284 | @c docstring begin (texi-doc-string "guile" "char<?") | |
1285 | @deffn primitive char<? x y | |
1286 | Return @code{#t} iff @var{x} is less than @var{y} in the ASCII sequence, | |
1287 | else @code{#f}. | |
1288 | @end deffn | |
1289 | ||
1290 | @c docstring begin (texi-doc-string "guile" "char<=?") | |
1291 | @deffn primitive char<=? x y | |
1292 | Return @code{#t} iff @var{x} is less than or equal to @var{y} in the | |
1293 | ASCII sequence, else @code{#f}. | |
1294 | @end deffn | |
1295 | ||
1296 | @c docstring begin (texi-doc-string "guile" "char>?") | |
1297 | @deffn primitive char>? x y | |
1298 | Return @code{#t} iff @var{x} is greater than @var{y} in the ASCII | |
1299 | sequence, else @code{#f}. | |
1300 | @end deffn | |
1301 | ||
1302 | @c docstring begin (texi-doc-string "guile" "char>=?") | |
1303 | @deffn primitive char>=? x y | |
1304 | Return @code{#t} iff @var{x} is greater than or equal to @var{y} in the | |
1305 | ASCII sequence, else @code{#f}. | |
1306 | @end deffn | |
1307 | ||
1308 | @c docstring begin (texi-doc-string "guile" "char-ci=?") | |
1309 | @deffn primitive char-ci=? x y | |
1310 | Return @code{#t} iff @var{x} is the same character as @var{y} ignoring | |
1311 | case, else @code{#f}. | |
1312 | @end deffn | |
1313 | ||
1314 | @c docstring begin (texi-doc-string "guile" "char-ci<?") | |
1315 | @deffn primitive char-ci<? x y | |
1316 | Return @code{#t} iff @var{x} is less than @var{y} in the ASCII sequence | |
1317 | ignoring case, else @code{#f}. | |
1318 | @end deffn | |
1319 | ||
1320 | @c docstring begin (texi-doc-string "guile" "char-ci<=?") | |
1321 | @deffn primitive char-ci<=? x y | |
1322 | Return @code{#t} iff @var{x} is less than or equal to @var{y} in the | |
1323 | ASCII sequence ignoring case, else @code{#f}. | |
1324 | @end deffn | |
1325 | ||
1326 | @c docstring begin (texi-doc-string "guile" "char-ci>?") | |
1327 | @deffn primitive char-ci>? x y | |
1328 | Return @code{#t} iff @var{x} is greater than @var{y} in the ASCII | |
1329 | sequence ignoring case, else @code{#f}. | |
1330 | @end deffn | |
1331 | ||
1332 | @c docstring begin (texi-doc-string "guile" "char-ci>=?") | |
1333 | @deffn primitive char-ci>=? x y | |
1334 | Return @code{#t} iff @var{x} is greater than or equal to @var{y} in the | |
1335 | ASCII sequence ignoring case, else @code{#f}. | |
1336 | @end deffn | |
1337 | ||
1338 | @c docstring begin (texi-doc-string "guile" "char-alphabetic?") | |
1339 | @deffn primitive char-alphabetic? chr | |
1340 | Return @code{#t} iff @var{chr} is alphabetic, else @code{#f}. | |
1341 | Alphabetic means the same thing as the isalpha C library function. | |
1342 | @end deffn | |
1343 | ||
1344 | @c docstring begin (texi-doc-string "guile" "char-numeric?") | |
1345 | @deffn primitive char-numeric? chr | |
1346 | Return @code{#t} iff @var{chr} is numeric, else @code{#f}. | |
1347 | Numeric means the same thing as the isdigit C library function. | |
1348 | @end deffn | |
1349 | ||
1350 | @c docstring begin (texi-doc-string "guile" "char-whitespace?") | |
1351 | @deffn primitive char-whitespace? chr | |
1352 | Return @code{#t} iff @var{chr} is whitespace, else @code{#f}. | |
1353 | Whitespace means the same thing as the isspace C library function. | |
1354 | @end deffn | |
1355 | ||
1356 | @c docstring begin (texi-doc-string "guile" "char-upper-case?") | |
1357 | @deffn primitive char-upper-case? chr | |
1358 | Return @code{#t} iff @var{chr} is uppercase, else @code{#f}. | |
1359 | Uppercase means the same thing as the isupper C library function. | |
1360 | @end deffn | |
1361 | ||
1362 | @c docstring begin (texi-doc-string "guile" "char-lower-case?") | |
1363 | @deffn primitive char-lower-case? chr | |
1364 | Return @code{#t} iff @var{chr} is lowercase, else @code{#f}. | |
1365 | Lowercase means the same thing as the islower C library function. | |
1366 | @end deffn | |
1367 | ||
1368 | @c docstring begin (texi-doc-string "guile" "char-is-both?") | |
1369 | @deffn primitive char-is-both? chr | |
1370 | Return @code{#t} iff @var{chr} is either uppercase or lowercase, else @code{#f}. | |
1371 | Uppercase and lowercase are as defined by the isupper and islower | |
1372 | C library functions. | |
1373 | @end deffn | |
1374 | ||
1375 | @c docstring begin (texi-doc-string "guile" "char->integer") | |
1376 | @deffn primitive char->integer chr | |
1377 | Return the number corresponding to ordinal position of @var{chr} in the | |
1378 | ASCII sequence. | |
1379 | @end deffn | |
1380 | ||
1381 | @c docstring begin (texi-doc-string "guile" "integer->char") | |
1382 | @deffn primitive integer->char n | |
1383 | Return the character at position @var{n} in the ASCII sequence. | |
1384 | @end deffn | |
1385 | ||
1386 | @c docstring begin (texi-doc-string "guile" "char-upcase") | |
1387 | @deffn primitive char-upcase chr | |
1388 | Return the uppercase character version of @var{chr}. | |
1389 | @end deffn | |
1390 | ||
1391 | @c docstring begin (texi-doc-string "guile" "char-downcase") | |
1392 | @deffn primitive char-downcase chr | |
1393 | Return the lowercase character version of @var{chr}. | |
1394 | @end deffn | |
1395 | ||
1396 | ||
1397 | @node Strings | |
1398 | @section Strings | |
1399 | ||
1400 | [FIXME: this is pasted in from Tom Lord's original guile.texi and should | |
1401 | be reviewed] | |
1402 | ||
1403 | For the sake of efficiency, two special kinds of strings are available | |
1404 | in Guile: shared substrings and the misleadingly named ``read-only'' | |
1405 | strings. It is not necessary to know about these to program in Guile, | |
1406 | but you are likely to run into one or both of these special string types | |
1407 | eventually, and it will be helpful to know how they work. | |
1408 | ||
1409 | @menu | |
1410 | * String Fun:: New functions for manipulating strings. | |
1411 | * Shared Substrings:: Strings which share memory with each other. | |
1412 | * Read Only Strings:: Treating certain non-strings as strings. | |
1413 | @end menu | |
1414 | ||
1415 | @node String Fun | |
1416 | @subsection String Fun | |
1417 | ||
fcaedf99 MG |
1418 | @r5index string |
1419 | @r5index list->string | |
38a93523 NJ |
1420 | @c docstring begin (texi-doc-string "guile" "string") |
1421 | @c docstring begin (texi-doc-string "guile" "list->string") | |
1422 | @deffn primitive string . chrs | |
1423 | @deffnx primitive list->string chrs | |
1424 | Returns a newly allocated string composed of the arguments, | |
1425 | @var{chrs}. | |
1426 | @end deffn | |
1427 | ||
fcaedf99 | 1428 | @r5index make-string |
38a93523 NJ |
1429 | @c docstring begin (texi-doc-string "guile" "make-string") |
1430 | @deffn primitive make-string k [chr] | |
1431 | Return a newly allocated string of | |
1432 | length @var{k}. If @var{chr} is given, then all elements of | |
1433 | the string are initialized to @var{chr}, otherwise the contents | |
1434 | of the @var{string} are unspecified. | |
1435 | @end deffn | |
1436 | ||
fcaedf99 | 1437 | @r5index string-append |
38a93523 NJ |
1438 | @c docstring begin (texi-doc-string "guile" "string-append") |
1439 | @deffn primitive string-append . args | |
1440 | Return a newly allocated string whose characters form the | |
1441 | concatenation of the given strings, @var{args}. | |
1442 | @end deffn | |
1443 | ||
fcaedf99 | 1444 | @r5index string-length |
38a93523 NJ |
1445 | @c docstring begin (texi-doc-string "guile" "string-length") |
1446 | @deffn primitive string-length string | |
1447 | Return the number of characters in @var{string}. | |
1448 | @end deffn | |
1449 | ||
fcaedf99 | 1450 | @r5index string-ref |
38a93523 NJ |
1451 | @c docstring begin (texi-doc-string "guile" "string-ref") |
1452 | @deffn primitive string-ref str k | |
1453 | Return character @var{k} of @var{str} using zero-origin | |
1454 | indexing. @var{k} must be a valid index of @var{str}. | |
1455 | @end deffn | |
1456 | ||
fcaedf99 | 1457 | @r5index string-set! |
38a93523 NJ |
1458 | @c docstring begin (texi-doc-string "guile" "string-set!") |
1459 | @deffn primitive string-set! str k chr | |
1460 | Store @var{chr} in element @var{k} of @var{str} and return | |
1461 | an unspecified value. @var{k} must be a valid index of | |
1462 | @var{str}. | |
1463 | @end deffn | |
1464 | ||
fcaedf99 | 1465 | @r5index string? |
38a93523 NJ |
1466 | @c docstring begin (texi-doc-string "guile" "string?") |
1467 | @deffn primitive string? obj | |
1468 | Returns @code{#t} iff @var{obj} is a string, else returns | |
1469 | @code{#f}. | |
1470 | @end deffn | |
1471 | ||
fcaedf99 | 1472 | @r5index substring |
38a93523 NJ |
1473 | @c docstring begin (texi-doc-string "guile" "substring") |
1474 | @deffn primitive substring str start [end] | |
1475 | Return a newly allocated string formed from the characters | |
1476 | of @var{str} beginning with index @var{start} (inclusive) and | |
1477 | ending with index @var{end} (exclusive). | |
1478 | @var{str} must be a string, @var{start} and @var{end} must be | |
1479 | exact integers satisfying: | |
1480 | ||
1481 | 0 <= @var{start} <= @var{end} <= (string-length @var{str}). | |
1482 | @end deffn | |
1483 | ||
1484 | @c docstring begin (texi-doc-string "guile" "string-index") | |
1485 | @deffn primitive string-index str chr [frm [to]] | |
1486 | Return the index of the first occurrence of @var{chr} in @var{str}. The | |
1487 | optional integer arguments @var{frm} and @var{to} limit the search to | |
1488 | a portion of the string. This procedure essentially implements the | |
1489 | @code{index} or @code{strchr} functions from the C library. | |
1490 | ||
1491 | (qdocs:) Returns the index of @var{char} in @var{str}, or @code{#f} if the | |
1492 | @var{char} isn't in @var{str}. If @var{frm} is given and not @code{#f}, | |
780ee65e | 1493 | it is used as the starting index; if @var{to} is given and not @code{#f}, |
38a93523 NJ |
1494 | it is used as the ending index (exclusive). |
1495 | ||
1496 | @example | |
1497 | (string-index "weiner" #\e) | |
1498 | @result{} 1 | |
1499 | ||
1500 | (string-index "weiner" #\e 2) | |
1501 | @result{} 4 | |
1502 | ||
1503 | (string-index "weiner" #\e 2 4) | |
1504 | @result{} #f | |
1505 | @end example | |
1506 | @end deffn | |
1507 | ||
1508 | @c docstring begin (texi-doc-string "guile" "string-rindex") | |
1509 | @deffn primitive string-rindex str chr [frm [to]] | |
1510 | Like @code{string-index}, but search from the right of the string rather | |
1511 | than from the left. This procedure essentially implements the | |
1512 | @code{rindex} or @code{strrchr} functions from the C library. | |
1513 | ||
1514 | (qdocs:) The same as @code{string-index}, except it gives the rightmost occurance | |
1515 | of @var{char} in the range [@var{frm}, @var{to}-1], which defaults to | |
1516 | the entire string. | |
1517 | ||
1518 | @example | |
1519 | (string-rindex "weiner" #\e) | |
1520 | @result{} 4 | |
1521 | ||
1522 | (string-rindex "weiner" #\e 2 4) | |
1523 | @result{} #f | |
1524 | ||
1525 | (string-rindex "weiner" #\e 2 5) | |
1526 | @result{} 4 | |
1527 | @end example | |
1528 | @end deffn | |
1529 | ||
1530 | @c docstring begin (texi-doc-string "guile" "substring-move!") | |
1531 | @c docstring begin (texi-doc-string "guile" "substring-move-left!") | |
1532 | @c docstring begin (texi-doc-string "guile" "substring-move-right!") | |
1533 | @deffn primitive substring-move! str1 start1 end1 str2 start2 | |
1534 | @deffnx primitive substring-move-left! str1 start1 end1 str2 start2 | |
1535 | @deffnx primitive substring-move-right! str1 start1 end1 str2 start2 | |
1536 | Copy the substring of @var{str1} bounded by @var{start1} and @var{end1} | |
1537 | into @var{str2} beginning at position @var{end2}. | |
1538 | @code{substring-move-right!} begins copying from the rightmost character | |
1539 | and moves left, and @code{substring-move-left!} copies from the leftmost | |
1540 | character moving right. | |
1541 | ||
1542 | It is useful to have two functions that copy in different directions so | |
1543 | that substrings can be copied back and forth within a single string. If | |
1544 | you wish to copy text from the left-hand side of a string to the | |
1545 | right-hand side of the same string, and the source and destination | |
1546 | overlap, you must be careful to copy the rightmost characters of the | |
1547 | text first, to avoid clobbering your data. Hence, when @var{str1} and | |
1548 | @var{str2} are the same string, you should use | |
1549 | @code{substring-move-right!} when moving text from left to right, and | |
1550 | @code{substring-move-left!} otherwise. If @code{str1} and @samp{str2} | |
1551 | are different strings, it does not matter which function you use. | |
1552 | @end deffn | |
1553 | ||
1554 | @deffn primitive substring-move-left! str1 start1 end1 str2 start2 | |
1555 | @end deffn | |
1556 | @deftypefn {C Function} SCM scm_substring_move_left_x (SCM @var{str1}, SCM @var{start1}, SCM @var{end1}, SCM @var{str2}, SCM @var{start2}) | |
1557 | [@strong{Note:} this is only valid if you've applied the strop patch]. | |
1558 | ||
1559 | Moves a substring of @var{str1}, from @var{start1} to @var{end1} | |
1560 | (@var{end1} is exclusive), into @var{str2}, starting at | |
1561 | @var{start2}. Allows overlapping strings. | |
1562 | ||
1563 | @example | |
1564 | (define x (make-string 10 #\a)) | |
1565 | (define y "bcd") | |
1566 | (substring-move-left! x 2 5 y 0) | |
1567 | y | |
1568 | @result{} "aaa" | |
1569 | ||
1570 | x | |
1571 | @result{} "aaaaaaaaaa" | |
1572 | ||
1573 | (define y "bcdefg") | |
1574 | (substring-move-left! x 2 5 y 0) | |
1575 | y | |
1576 | @result{} "aaaefg" | |
1577 | ||
1578 | (define y "abcdefg") | |
1579 | (substring-move-left! y 2 5 y 3) | |
1580 | y | |
1581 | @result{} "abccccg" | |
1582 | @end example | |
1583 | @end deftypefn | |
1584 | ||
1585 | @deffn substring-move-right! str1 start1 end1 str2 start2 | |
1586 | @end deffn | |
1587 | @deftypefn {C Function} SCM scm_substring_move_right_x (SCM @var{str1}, SCM @var{start1}, SCM @var{end1}, SCM @var{str2}, SCM @var{start2}) | |
1588 | [@strong{Note:} this is only valid if you've applied the strop patch, if | |
1589 | it hasn't made it into the guile tree]. | |
1590 | ||
1591 | Does much the same thing as @code{substring-move-left!}, except it | |
1592 | starts moving at the end of the sequence, rather than the beginning. | |
1593 | @example | |
1594 | (define y "abcdefg") | |
1595 | (substring-move-right! y 2 5 y 0) | |
1596 | y | |
1597 | @result{} "ededefg" | |
1598 | ||
1599 | (define y "abcdefg") | |
1600 | (substring-move-right! y 2 5 y 3) | |
1601 | y | |
1602 | @result{} "abccdeg" | |
1603 | @end example | |
1604 | @end deftypefn | |
1605 | ||
1606 | @c docstring begin (texi-doc-string "guile" "vector-move-left!") | |
1607 | @deffn primitive vector-move-left! vec1 start1 end1 vec2 start2 | |
1608 | Vector version of @code{substring-move-left!}. | |
1609 | @end deffn | |
1610 | ||
1611 | @c docstring begin (texi-doc-string "guile" "vector-move-right!") | |
1612 | @deffn primitive vector-move-right! vec1 start1 end1 vec2 start2 | |
1613 | Vector version of @code{substring-move-right!}. | |
1614 | @end deffn | |
1615 | ||
1616 | @c ARGFIXME fill/fill-char | |
1617 | @c docstring begin (texi-doc-string "guile" "substring-fill!") | |
1618 | @deffn primitive substring-fill! str start end fill | |
1619 | Change every character in @var{str} between @var{start} and @var{end} to | |
1620 | @var{fill-char}. | |
1621 | ||
1622 | (qdocs:) Destructively fills @var{str}, from @var{start} to @var{end}, with @var{fill}. | |
1623 | ||
1624 | @example | |
1625 | (define y "abcdefg") | |
1626 | (substring-fill! y 1 3 #\r) | |
1627 | y | |
1628 | @result{} "arrdefg" | |
1629 | @end example | |
1630 | @end deffn | |
1631 | ||
1632 | @c docstring begin (texi-doc-string "guile" "string-null?") | |
1633 | @deffn primitive string-null? str | |
1634 | Return @code{#t} if @var{str}'s length is nonzero, and @code{#f} | |
1635 | otherwise. | |
1636 | ||
1637 | (qdocs:) Returns @code{#t} if @var{str} is empty, else returns @code{#f}. | |
1638 | ||
1639 | @example | |
1640 | (string-null? "") | |
1641 | @result{} #t | |
1642 | ||
1643 | (string-null? y) | |
1644 | @result{} #f | |
1645 | @end example | |
1646 | @end deffn | |
1647 | ||
1648 | @c ARGFIXME v/str | |
1649 | @c docstring begin (texi-doc-string "guile" "string-upcase!") | |
1650 | @deffn primitive string-upcase! str | |
1651 | Destructively upcase every character in @code{str}. | |
1652 | ||
1653 | (qdocs:) Converts each element in @var{str} to upper case. | |
1654 | ||
1655 | @example | |
1656 | (string-upcase! y) | |
1657 | @result{} "ARRDEFG" | |
1658 | ||
1659 | y | |
1660 | @result{} "ARRDEFG" | |
1661 | @end example | |
1662 | @end deffn | |
1663 | ||
1664 | @c docstring begin (texi-doc-string "guile" "string-upcase") | |
1665 | @deffn primitive string-upcase str | |
1666 | Upcase every character in @code{str}. | |
1667 | @end deffn | |
1668 | ||
1669 | @c ARGFIXME v/str | |
1670 | @c docstring begin (texi-doc-string "guile" "string-downcase!") | |
1671 | @deffn primitive string-downcase! str | |
1672 | Destructively downcase every character in @code{str}. | |
1673 | ||
1674 | (qdocs:) Converts each element in @var{str} to lower case. | |
1675 | ||
1676 | @example | |
1677 | y | |
1678 | @result{} "ARRDEFG" | |
1679 | ||
1680 | (string-downcase! y) | |
1681 | @result{} "arrdefg" | |
1682 | ||
1683 | y | |
1684 | @result{} "arrdefg" | |
1685 | @end example | |
1686 | @end deffn | |
1687 | ||
1688 | @c docstring begin (texi-doc-string "guile" "string-downcase") | |
1689 | @deffn primitive string-downcase str | |
1690 | Downcase every character in @code{str}. | |
1691 | @end deffn | |
1692 | ||
1693 | @c docstring begin (texi-doc-string "guile" "string-capitalize!") | |
1694 | @deffn primitive string-capitalize! str | |
1695 | Destructively capitalize every character in @code{str}. | |
1696 | @end deffn | |
1697 | ||
1698 | @c docstring begin (texi-doc-string "guile" "string-capitalize") | |
1699 | @deffn primitive string-capitalize str | |
1700 | Capitalize every character in @code{str}. | |
1701 | @end deffn | |
1702 | ||
fcaedf99 | 1703 | @r5index string<=? |
38a93523 NJ |
1704 | @c docstring begin (texi-doc-string "guile" "string-ci<=?") |
1705 | @deffn primitive string-ci<=? s1 s2 | |
1706 | Case insensitive lexicographic ordering predicate; | |
780ee65e | 1707 | returns @code{#t} if @var{s1} is lexicographically less than |
38a93523 NJ |
1708 | or equal to @var{s2} regardless of case. (r5rs) |
1709 | @end deffn | |
1710 | ||
fcaedf99 | 1711 | @r5index string-ci< |
38a93523 NJ |
1712 | @c docstring begin (texi-doc-string "guile" "string-ci<?") |
1713 | @deffn primitive string-ci<? s1 s2 | |
1714 | Case insensitive lexicographic ordering predicate; | |
780ee65e | 1715 | returns @code{#t} if @var{s1} is lexicographically less than |
38a93523 NJ |
1716 | @var{s2} regardless of case. (r5rs) |
1717 | @end deffn | |
1718 | ||
fcaedf99 | 1719 | @r5index string-ci=? |
38a93523 NJ |
1720 | @c docstring begin (texi-doc-string "guile" "string-ci=?") |
1721 | @deffn primitive string-ci=? s1 s2 | |
780ee65e NJ |
1722 | Case-insensitive string equality predicate; returns @code{#t} |
1723 | if the two strings are the same length and their component | |
1724 | characters match (ignoring case) at each position; otherwise | |
1725 | returns @code{#f}. (r5rs) | |
38a93523 NJ |
1726 | @end deffn |
1727 | ||
fcaedf99 | 1728 | @r5index string-ci>=? |
38a93523 NJ |
1729 | @c docstring begin (texi-doc-string "guile" "string-ci>=?") |
1730 | @deffn primitive string-ci>=? s1 s2 | |
1731 | Case insensitive lexicographic ordering predicate; | |
780ee65e NJ |
1732 | returns @code{#t} if @var{s1} is lexicographically greater |
1733 | than or equal to @var{s2} regardless of case. (r5rs) | |
38a93523 NJ |
1734 | @end deffn |
1735 | ||
fcaedf99 | 1736 | @r5index string-ci>? |
38a93523 NJ |
1737 | @c docstring begin (texi-doc-string "guile" "string-ci>?") |
1738 | @deffn primitive string-ci>? s1 s2 | |
1739 | Case insensitive lexicographic ordering predicate; | |
780ee65e NJ |
1740 | returns @code{#t} if @var{s1} is lexicographically greater |
1741 | than @var{s2} regardless of case. (r5rs) | |
38a93523 NJ |
1742 | @end deffn |
1743 | ||
fcaedf99 | 1744 | @r5index string<=? |
38a93523 NJ |
1745 | @c docstring begin (texi-doc-string "guile" "string<=?") |
1746 | @deffn primitive string<=? s1 s2 | |
780ee65e NJ |
1747 | Lexicographic ordering predicate; returns @code{#t} if |
1748 | @var{s1} is lexicographically less than or equal to @var{s2}. | |
1749 | (r5rs) | |
38a93523 NJ |
1750 | @end deffn |
1751 | ||
fcaedf99 | 1752 | @r5index string<? |
38a93523 NJ |
1753 | @c docstring begin (texi-doc-string "guile" "string<?") |
1754 | @deffn primitive string<? s1 s2 | |
780ee65e NJ |
1755 | Lexicographic ordering predicate; returns @code{#t} if |
1756 | @var{s1} is lexicographically less than @var{s2}. (r5rs) | |
38a93523 NJ |
1757 | @end deffn |
1758 | ||
fcaedf99 | 1759 | @r5index string=? |
38a93523 NJ |
1760 | @c docstring begin (texi-doc-string "guile" "string=?") |
1761 | @deffn primitive string=? s1 s2 | |
1762 | Lexicographic equality predicate; | |
780ee65e NJ |
1763 | Returns @code{#t} if the two strings are the same length and |
1764 | contain the same characters in the same positions, otherwise | |
1765 | returns @code{#f}. (r5rs) | |
38a93523 | 1766 | |
780ee65e NJ |
1767 | The procedure @code{string-ci=?} treats upper and lower case |
1768 | letters as though they were the same character, but | |
1769 | @code{string=?} treats upper and lower case as distinct | |
1770 | characters. | |
38a93523 NJ |
1771 | @end deffn |
1772 | ||
fcaedf99 | 1773 | @r5index string>=? |
38a93523 NJ |
1774 | @c docstring begin (texi-doc-string "guile" "string>=?") |
1775 | @deffn primitive string>=? s1 s2 | |
780ee65e NJ |
1776 | Lexicographic ordering predicate; returns @code{#t} if |
1777 | @var{s1} is lexicographically greater than or equal to | |
1778 | @var{s2}. (r5rs) | |
38a93523 NJ |
1779 | @end deffn |
1780 | ||
fcaedf99 | 1781 | @r5index string>? |
38a93523 NJ |
1782 | @c docstring begin (texi-doc-string "guile" "string>?") |
1783 | @deffn primitive string>? s1 s2 | |
780ee65e NJ |
1784 | Lexicographic ordering predicate; returns @code{#t} if |
1785 | @var{s1} is lexicographically greater than @var{s2}. (r5rs) | |
38a93523 NJ |
1786 | @end deffn |
1787 | ||
fcaedf99 | 1788 | @r5index string->list |
38a93523 NJ |
1789 | @c docstring begin (texi-doc-string "guile" "string->list") |
1790 | @deffn primitive string->list str | |
1791 | @samp{String->list} returns a newly allocated list of the | |
1792 | characters that make up the given string. @samp{List->string} | |
1793 | returns a newly allocated string formed from the characters in the list | |
1794 | @var{list}, which must be a list of characters. @samp{String->list} | |
1795 | and @samp{list->string} are | |
1796 | inverses so far as @samp{equal?} is concerned. (r5rs) | |
1797 | @end deffn | |
1798 | ||
1799 | @c docstring begin (texi-doc-string "guile" "string-ci->symbol") | |
1800 | @deffn primitive string-ci->symbol str | |
1801 | Return the symbol whose name is @var{str}, downcased in necessary(???). | |
1802 | @end deffn | |
1803 | ||
fcaedf99 | 1804 | @r5index string-copy |
38a93523 NJ |
1805 | @c docstring begin (texi-doc-string "guile" "string-copy") |
1806 | @deffn primitive string-copy str | |
1807 | Returns a newly allocated copy of the given @var{string}. (r5rs) | |
1808 | @end deffn | |
1809 | ||
fcaedf99 | 1810 | @r5index string-fill! |
38a93523 NJ |
1811 | @c docstring begin (texi-doc-string "guile" "string-fill!") |
1812 | @deffn primitive string-fill! str chr | |
1813 | Stores @var{char} in every element of the given @var{string} and returns an | |
1814 | unspecified value. (r5rs) | |
1815 | @end deffn | |
1816 | ||
1817 | ||
1818 | @node Shared Substrings | |
1819 | @subsection Shared Substrings | |
1820 | ||
1821 | Whenever you extract a substring using @code{substring}, the Scheme | |
1822 | interpreter allocates a new string and copies data from the old string. | |
1823 | This is expensive, but @code{substring} is so convenient for | |
1824 | manipulating text that programmers use it often. | |
1825 | ||
1826 | Guile Scheme provides the concept of the @dfn{shared substring} to | |
1827 | improve performance of many substring-related operations. A shared | |
1828 | substring is an object that mostly behaves just like an ordinary | |
1829 | substring, except that it actually shares storage space with its parent | |
1830 | string. | |
1831 | ||
1832 | @c ARGFIXME frm/start to/end | |
1833 | @c docstring begin (texi-doc-string "guile" "make-shared-substring") | |
1834 | @deffn primitive make-shared-substring str [frm [to]] | |
1835 | Return a shared substring of @var{str}. The semantics are the same as | |
1836 | for the @code{substring} function: the shared substring returned | |
1837 | includes all of the text from @var{str} between indexes @var{start} | |
1838 | (inclusive) and @var{end} (exclusive). If @var{end} is omitted, it | |
1839 | defaults to the end of @var{str}. The shared substring returned by | |
1840 | @code{make-shared-substring} occupies the same storage space as | |
1841 | @var{str}. | |
1842 | @end deffn | |
1843 | ||
1844 | Example: | |
1845 | ||
1846 | @example | |
1847 | (define foo "the quick brown fox") | |
1848 | (define bar (make-shared-substring some-string 4 9)) | |
1849 | ||
1850 | foo => "t h e q u i c k b r o w n f o x" | |
1851 | bar =========> |---------| | |
1852 | @end example | |
1853 | ||
1854 | The shared substring @var{bar} is not given its own storage space. | |
1855 | Instead, the Guile interpreter notes internally that @var{bar} points to | |
1856 | a portion of the memory allocated to @var{foo}. However, @var{bar} | |
1857 | behaves like an ordinary string in most respects: it may be used with | |
1858 | string primitives like @code{string-length}, @code{string-ref}, | |
1859 | @code{string=?}. Guile makes the necessary translation between indices | |
1860 | of @var{bar} and indices of @var{foo} automatically. | |
1861 | ||
1862 | @example | |
1863 | (string-length? bar) @result{} 5 ; bar only extends from indices 4 to 9 | |
1864 | (string-ref bar 3) @result{} #\c ; same as (string-ref foo 7) | |
1865 | (make-shared-substring bar 2) | |
1866 | @result{} "ick" ; can even make a shared substring! | |
1867 | @end example | |
1868 | ||
1869 | Because creating a shared substring does not require allocating new | |
1870 | storage from the heap, it is a very fast operation. However, because it | |
1871 | shares memory with its parent string, a change to the contents of the | |
1872 | parent string will implicitly change the contents of its shared | |
1873 | substrings. | |
1874 | ||
1875 | @example | |
1876 | (string-set! foo 7 #\r) | |
1877 | bar @result{} "quirk" | |
1878 | @end example | |
1879 | ||
1880 | Guile considers shared substrings to be immutable. This is because | |
1881 | programmers might not always be aware that a given string is really a | |
1882 | shared substring, and might innocently try to mutate it without | |
1883 | realizing that the change would affect its parent string. (We are | |
1884 | currently considering a "copy-on-write" strategy that would permit | |
1885 | modifying shared substrings without affecting the parent string.) | |
1886 | ||
1887 | In general, shared substrings are useful in circumstances where it is | |
1888 | important to divide a string into smaller portions, but you do not | |
1889 | expect to change the contents of any of the strings involved. | |
1890 | ||
1891 | @node Read Only Strings | |
1892 | @subsection Read Only Strings | |
1893 | ||
1894 | Type-checking in Guile primitives distinguishes between mutable strings | |
1895 | and read only strings. Mutable strings answer @code{#t} to | |
1896 | @code{string?} while read only strings may or may not. All kinds of | |
1897 | strings, whether or not they are mutable return #t to this: | |
1898 | ||
1899 | @c ARGFIXME x/obj | |
1900 | @c docstring begin (texi-doc-string "guile" "read-only-string?") | |
1901 | @deffn primitive read-only-string? obj | |
1902 | Return true if @var{obj} can be read as a string, | |
1903 | ||
1904 | This illustrates the difference between @code{string?} and | |
1905 | @code{read-only-string?}: | |
1906 | ||
1907 | @example | |
1908 | (string? "a string") @result{} #t | |
1909 | (string? 'a-symbol) @result{} #f | |
1910 | ||
1911 | (read-only-string? "a string") @result{} #t | |
1912 | (read-only-string? 'a-symbol) @result{} #t | |
1913 | @end example | |
1914 | @end deffn | |
1915 | ||
1916 | "Read-only" refers to how the string will be used, not how the string is | |
1917 | permitted to be used. In particular, all strings are "read-only | |
1918 | strings" even if they are mutable, because a function that only reads | |
1919 | from a string can certainly operate on even a mutable string. | |
1920 | ||
1921 | Symbols are an example of read-only strings. Many string functions, | |
1922 | such as @code{string-append} are happy to operate on symbols. Many | |
1923 | functions that expect a string argument, such as @code{open-file}, will | |
1924 | accept a symbol as well. | |
1925 | ||
1926 | Shared substrings, discussed in the previous chapter, also happen to be | |
1927 | read-only strings. | |
1928 | ||
1929 | ||
1930 | @node Regular Expressions | |
1931 | @section Regular Expressions | |
1932 | ||
1933 | @cindex regular expressions | |
1934 | @cindex regex | |
1935 | @cindex emacs regexp | |
1936 | ||
1937 | A @dfn{regular expression} (or @dfn{regexp}) is a pattern that | |
1938 | describes a whole class of strings. A full description of regular | |
1939 | expressions and their syntax is beyond the scope of this manual; | |
1940 | an introduction can be found in the Emacs manual (@pxref{Regexps, | |
1941 | , Syntax of Regular Expressions, emacs, The GNU Emacs Manual}, or | |
1942 | in many general Unix reference books. | |
1943 | ||
1944 | If your system does not include a POSIX regular expression library, and | |
1945 | you have not linked Guile with a third-party regexp library such as Rx, | |
1946 | these functions will not be available. You can tell whether your Guile | |
1947 | installation includes regular expression support by checking whether the | |
1948 | @code{*features*} list includes the @code{regex} symbol. | |
1949 | ||
1950 | @menu | |
1951 | * Regexp Functions:: Functions that create and match regexps. | |
1952 | * Match Structures:: Finding what was matched by a regexp. | |
1953 | * Backslash Escapes:: Removing the special meaning of regexp metacharacters. | |
1954 | * Rx Interface:: Tom Lord's Rx library does things differently. | |
1955 | @end menu | |
1956 | ||
1957 | [FIXME: it may be useful to include an Examples section. Parts of this | |
1958 | interface are bewildering on first glance.] | |
1959 | ||
1960 | @node Regexp Functions | |
1961 | @subsection Regexp Functions | |
1962 | ||
1963 | By default, Guile supports POSIX extended regular expressions. | |
1964 | That means that the characters @samp{(}, @samp{)}, @samp{+} and | |
1965 | @samp{?} are special, and must be escaped if you wish to match the | |
1966 | literal characters. | |
1967 | ||
1968 | This regular expression interface was modeled after that | |
1969 | implemented by SCSH, the Scheme Shell. It is intended to be | |
1970 | upwardly compatible with SCSH regular expressions. | |
1971 | ||
1972 | @c begin (scm-doc-string "regex.scm" "string-match") | |
1973 | @deffn procedure string-match pattern str [start] | |
1974 | Compile the string @var{pattern} into a regular expression and compare | |
1975 | it with @var{str}. The optional numeric argument @var{start} specifies | |
1976 | the position of @var{str} at which to begin matching. | |
1977 | ||
1978 | @code{string-match} returns a @dfn{match structure} which | |
1979 | describes what, if anything, was matched by the regular | |
1980 | expression. @xref{Match Structures}. If @var{str} does not match | |
1981 | @var{pattern} at all, @code{string-match} returns @code{#f}. | |
1982 | @end deffn | |
1983 | ||
1984 | Each time @code{string-match} is called, it must compile its | |
1985 | @var{pattern} argument into a regular expression structure. This | |
1986 | operation is expensive, which makes @code{string-match} inefficient if | |
1987 | the same regular expression is used several times (for example, in a | |
1988 | loop). For better performance, you can compile a regular expression in | |
1989 | advance and then match strings against the compiled regexp. | |
1990 | ||
1991 | @c ARGFIXME pat/str flags/flag | |
1992 | @c docstring begin (texi-doc-string "guile" "make-regexp") | |
1993 | @deffn primitive make-regexp pat . flags | |
1994 | Compile the regular expression described by @var{str}, and return the | |
1995 | compiled regexp structure. If @var{str} does not describe a legal | |
1996 | regular expression, @code{make-regexp} throws a | |
1997 | @code{regular-expression-syntax} error. | |
1998 | ||
1999 | The @var{flag} arguments change the behavior of the compiled regexp. | |
2000 | The following flags may be supplied: | |
2001 | ||
2002 | @table @code | |
2003 | @item regexp/icase | |
2004 | Consider uppercase and lowercase letters to be the same when matching. | |
2005 | ||
2006 | @item regexp/newline | |
2007 | If a newline appears in the target string, then permit the @samp{^} and | |
2008 | @samp{$} operators to match immediately after or immediately before the | |
2009 | newline, respectively. Also, the @samp{.} and @samp{[^...]} operators | |
2010 | will never match a newline character. The intent of this flag is to | |
2011 | treat the target string as a buffer containing many lines of text, and | |
2012 | the regular expression as a pattern that may match a single one of those | |
2013 | lines. | |
2014 | ||
2015 | @item regexp/basic | |
2016 | Compile a basic (``obsolete'') regexp instead of the extended | |
2017 | (``modern'') regexps that are the default. Basic regexps do not | |
2018 | consider @samp{|}, @samp{+} or @samp{?} to be special characters, and | |
2019 | require the @samp{@{...@}} and @samp{(...)} metacharacters to be | |
2020 | backslash-escaped (@pxref{Backslash Escapes}). There are several other | |
2021 | differences between basic and extended regular expressions, but these | |
2022 | are the most significant. | |
2023 | ||
2024 | @item regexp/extended | |
2025 | Compile an extended regular expression rather than a basic regexp. This | |
2026 | is the default behavior; this flag will not usually be needed. If a | |
2027 | call to @code{make-regexp} includes both @code{regexp/basic} and | |
2028 | @code{regexp/extended} flags, the one which comes last will override | |
2029 | the earlier one. | |
2030 | @end table | |
2031 | @end deffn | |
2032 | ||
2033 | @c ARGFIXME rx/regexp | |
2034 | @c docstring begin (texi-doc-string "guile" "regexp-exec") | |
2035 | @deffn primitive regexp-exec rx str [start [flags]] | |
2036 | Match the compiled regular expression @var{regexp} against @code{str}. | |
2037 | If the optional integer @var{start} argument is provided, begin matching | |
2038 | from that position in the string. Return a match structure describing | |
2039 | the results of the match, or @code{#f} if no match could be found. | |
2040 | @end deffn | |
2041 | ||
2042 | @c ARGFIXME x/obj | |
2043 | @c docstring begin (texi-doc-string "guile" "regexp?") | |
2044 | @deffn primitive regexp? x | |
2045 | Return @code{#t} if @var{obj} is a compiled regular expression, or | |
2046 | @code{#f} otherwise. | |
2047 | @end deffn | |
2048 | ||
2049 | Regular expressions are commonly used to find patterns in one string and | |
2050 | replace them with the contents of another string. | |
2051 | ||
2052 | @c begin (scm-doc-string "regex.scm" "regexp-substitute") | |
2053 | @deffn procedure regexp-substitute port match [item@dots{}] | |
2054 | Write to the output port @var{port} selected contents of the match | |
2055 | structure @var{match}. Each @var{item} specifies what should be | |
2056 | written, and may be one of the following arguments: | |
2057 | ||
2058 | @itemize @bullet | |
2059 | @item | |
2060 | A string. String arguments are written out verbatim. | |
2061 | ||
2062 | @item | |
2063 | An integer. The submatch with that number is written. | |
2064 | ||
2065 | @item | |
2066 | The symbol @samp{pre}. The portion of the matched string preceding | |
2067 | the regexp match is written. | |
2068 | ||
2069 | @item | |
2070 | The symbol @samp{post}. The portion of the matched string following | |
2071 | the regexp match is written. | |
2072 | @end itemize | |
2073 | ||
2074 | @var{port} may be @code{#f}, in which case nothing is written; instead, | |
2075 | @code{regexp-substitute} constructs a string from the specified | |
2076 | @var{item}s and returns that. | |
2077 | @end deffn | |
2078 | ||
2079 | @c begin (scm-doc-string "regex.scm" "regexp-substitute") | |
2080 | @deffn procedure regexp-substitute/global port regexp target [item@dots{}] | |
2081 | Similar to @code{regexp-substitute}, but can be used to perform global | |
2082 | substitutions on @var{str}. Instead of taking a match structure as an | |
2083 | argument, @code{regexp-substitute/global} takes two string arguments: a | |
2084 | @var{regexp} string describing a regular expression, and a @var{target} | |
2085 | string which should be matched against this regular expression. | |
2086 | ||
2087 | Each @var{item} behaves as in @var{regexp-substitute}, with the | |
2088 | following exceptions: | |
2089 | ||
2090 | @itemize @bullet | |
2091 | @item | |
2092 | A function may be supplied. When this function is called, it will be | |
2093 | passed one argument: a match structure for a given regular expression | |
2094 | match. It should return a string to be written out to @var{port}. | |
2095 | ||
2096 | @item | |
2097 | The @samp{post} symbol causes @code{regexp-substitute/global} to recurse | |
2098 | on the unmatched portion of @var{str}. This @emph{must} be supplied in | |
2099 | order to perform global search-and-replace on @var{str}; if it is not | |
2100 | present among the @var{item}s, then @code{regexp-substitute/global} will | |
2101 | return after processing a single match. | |
2102 | @end itemize | |
2103 | @end deffn | |
2104 | ||
2105 | @node Match Structures | |
2106 | @subsection Match Structures | |
2107 | ||
2108 | @cindex match structures | |
2109 | ||
2110 | A @dfn{match structure} is the object returned by @code{string-match} and | |
2111 | @code{regexp-exec}. It describes which portion of a string, if any, | |
2112 | matched the given regular expression. Match structures include: a | |
2113 | reference to the string that was checked for matches; the starting and | |
2114 | ending positions of the regexp match; and, if the regexp included any | |
2115 | parenthesized subexpressions, the starting and ending positions of each | |
2116 | submatch. | |
2117 | ||
2118 | In each of the regexp match functions described below, the @code{match} | |
2119 | argument must be a match structure returned by a previous call to | |
2120 | @code{string-match} or @code{regexp-exec}. Most of these functions | |
2121 | return some information about the original target string that was | |
2122 | matched against a regular expression; we will call that string | |
2123 | @var{target} for easy reference. | |
2124 | ||
2125 | @c begin (scm-doc-string "regex.scm" "regexp-match?") | |
2126 | @deffn procedure regexp-match? obj | |
2127 | Return @code{#t} if @var{obj} is a match structure returned by a | |
2128 | previous call to @code{regexp-exec}, or @code{#f} otherwise. | |
2129 | @end deffn | |
2130 | ||
2131 | @c begin (scm-doc-string "regex.scm" "match:substring") | |
2132 | @deffn procedure match:substring match [n] | |
2133 | Return the portion of @var{target} matched by subexpression number | |
2134 | @var{n}. Submatch 0 (the default) represents the entire regexp match. | |
2135 | If the regular expression as a whole matched, but the subexpression | |
2136 | number @var{n} did not match, return @code{#f}. | |
2137 | @end deffn | |
2138 | ||
2139 | @c begin (scm-doc-string "regex.scm" "match:start") | |
2140 | @deffn procedure match:start match [n] | |
2141 | Return the starting position of submatch number @var{n}. | |
2142 | @end deffn | |
2143 | ||
2144 | @c begin (scm-doc-string "regex.scm" "match:end") | |
2145 | @deffn procedure match:end match [n] | |
2146 | Return the ending position of submatch number @var{n}. | |
2147 | @end deffn | |
2148 | ||
2149 | @c begin (scm-doc-string "regex.scm" "match:prefix") | |
2150 | @deffn procedure match:prefix match | |
2151 | Return the unmatched portion of @var{target} preceding the regexp match. | |
2152 | @end deffn | |
2153 | ||
2154 | @c begin (scm-doc-string "regex.scm" "match:suffix") | |
2155 | @deffn procedure match:suffix match | |
2156 | Return the unmatched portion of @var{target} following the regexp match. | |
2157 | @end deffn | |
2158 | ||
2159 | @c begin (scm-doc-string "regex.scm" "match:count") | |
2160 | @deffn procedure match:count match | |
2161 | Return the number of parenthesized subexpressions from @var{match}. | |
2162 | Note that the entire regular expression match itself counts as a | |
2163 | subexpression, and failed submatches are included in the count. | |
2164 | @end deffn | |
2165 | ||
2166 | @c begin (scm-doc-string "regex.scm" "match:string") | |
2167 | @deffn procedure match:string match | |
2168 | Return the original @var{target} string. | |
2169 | @end deffn | |
2170 | ||
2171 | @node Backslash Escapes | |
2172 | @subsection Backslash Escapes | |
2173 | ||
2174 | Sometimes you will want a regexp to match characters like @samp{*} or | |
2175 | @samp{$} exactly. For example, to check whether a particular string | |
2176 | represents a menu entry from an Info node, it would be useful to match | |
2177 | it against a regexp like @samp{^* [^:]*::}. However, this won't work; | |
2178 | because the asterisk is a metacharacter, it won't match the @samp{*} at | |
2179 | the beginning of the string. In this case, we want to make the first | |
2180 | asterisk un-magic. | |
2181 | ||
2182 | You can do this by preceding the metacharacter with a backslash | |
2183 | character @samp{\}. (This is also called @dfn{quoting} the | |
2184 | metacharacter, and is known as a @dfn{backslash escape}.) When Guile | |
2185 | sees a backslash in a regular expression, it considers the following | |
2186 | glyph to be an ordinary character, no matter what special meaning it | |
2187 | would ordinarily have. Therefore, we can make the above example work by | |
2188 | changing the regexp to @samp{^\* [^:]*::}. The @samp{\*} sequence tells | |
2189 | the regular expression engine to match only a single asterisk in the | |
2190 | target string. | |
2191 | ||
2192 | Since the backslash is itself a metacharacter, you may force a regexp to | |
2193 | match a backslash in the target string by preceding the backslash with | |
2194 | itself. For example, to find variable references in a @TeX{} program, | |
2195 | you might want to find occurrences of the string @samp{\let\} followed | |
2196 | by any number of alphabetic characters. The regular expression | |
2197 | @samp{\\let\\[A-Za-z]*} would do this: the double backslashes in the | |
2198 | regexp each match a single backslash in the target string. | |
2199 | ||
2200 | @c begin (scm-doc-string "regex.scm" "regexp-quote") | |
2201 | @deffn procedure regexp-quote str | |
2202 | Quote each special character found in @var{str} with a backslash, and | |
2203 | return the resulting string. | |
2204 | @end deffn | |
2205 | ||
2206 | @strong{Very important:} Using backslash escapes in Guile source code | |
2207 | (as in Emacs Lisp or C) can be tricky, because the backslash character | |
2208 | has special meaning for the Guile reader. For example, if Guile | |
2209 | encounters the character sequence @samp{\n} in the middle of a string | |
2210 | while processing Scheme code, it replaces those characters with a | |
2211 | newline character. Similarly, the character sequence @samp{\t} is | |
2212 | replaced by a horizontal tab. Several of these @dfn{escape sequences} | |
2213 | are processed by the Guile reader before your code is executed. | |
2214 | Unrecognized escape sequences are ignored: if the characters @samp{\*} | |
2215 | appear in a string, they will be translated to the single character | |
2216 | @samp{*}. | |
2217 | ||
2218 | This translation is obviously undesirable for regular expressions, since | |
2219 | we want to be able to include backslashes in a string in order to | |
2220 | escape regexp metacharacters. Therefore, to make sure that a backslash | |
2221 | is preserved in a string in your Guile program, you must use @emph{two} | |
2222 | consecutive backslashes: | |
2223 | ||
2224 | @lisp | |
2225 | (define Info-menu-entry-pattern (make-regexp "^\\* [^:]*")) | |
2226 | @end lisp | |
2227 | ||
2228 | The string in this example is preprocessed by the Guile reader before | |
2229 | any code is executed. The resulting argument to @code{make-regexp} is | |
2230 | the string @samp{^\* [^:]*}, which is what we really want. | |
2231 | ||
2232 | This also means that in order to write a regular expression that matches | |
2233 | a single backslash character, the regular expression string in the | |
2234 | source code must include @emph{four} backslashes. Each consecutive pair | |
2235 | of backslashes gets translated by the Guile reader to a single | |
2236 | backslash, and the resulting double-backslash is interpreted by the | |
2237 | regexp engine as matching a single backslash character. Hence: | |
2238 | ||
2239 | @lisp | |
2240 | (define tex-variable-pattern (make-regexp "\\\\let\\\\=[A-Za-z]*")) | |
2241 | @end lisp | |
2242 | ||
2243 | The reason for the unwieldiness of this syntax is historical. Both | |
2244 | regular expression pattern matchers and Unix string processing systems | |
2245 | have traditionally used backslashes with the special meanings | |
2246 | described above. The POSIX regular expression specification and ANSI C | |
2247 | standard both require these semantics. Attempting to abandon either | |
2248 | convention would cause other kinds of compatibility problems, possibly | |
2249 | more severe ones. Therefore, without extending the Scheme reader to | |
2250 | support strings with different quoting conventions (an ungainly and | |
2251 | confusing extension when implemented in other languages), we must adhere | |
2252 | to this cumbersome escape syntax. | |
2253 | ||
2254 | @node Rx Interface | |
2255 | @subsection Rx Interface | |
2256 | ||
2257 | [FIXME: this is taken from Gary and Mark's quick summaries and should be | |
2258 | reviewed and expanded. Rx is pretty stable, so could already be done!] | |
2259 | ||
2260 | @cindex rx | |
2261 | @cindex finite automaton | |
2262 | ||
2263 | Guile includes an interface to Tom Lord's Rx library (currently only to | |
2264 | POSIX regular expressions). Use of the library requires a two step | |
2265 | process: compile a regular expression into an efficient structure, then | |
2266 | use the structure in any number of string comparisons. | |
2267 | ||
2268 | For example, given the | |
2269 | regular expression @samp{abc.} (which matches any string containing | |
2270 | @samp{abc} followed by any single character): | |
2271 | ||
2272 | @smalllisp | |
2273 | guile> @kbd{(define r (regcomp "abc."))} | |
2274 | guile> @kbd{r} | |
2275 | #<rgx abc.> | |
2276 | guile> @kbd{(regexec r "abc")} | |
2277 | #f | |
2278 | guile> @kbd{(regexec r "abcd")} | |
2279 | #((0 . 4)) | |
2280 | guile> | |
2281 | @end smalllisp | |
2282 | ||
2283 | The definitions of @code{regcomp} and @code{regexec} are as follows: | |
2284 | ||
2285 | @c NJFIXME not in libguile! | |
2286 | @deffn primitive regcomp pattern [flags] | |
2287 | Compile the regular expression pattern using POSIX rules. Flags is | |
2288 | optional and should be specified using symbolic names: | |
2289 | @defvar REG_EXTENDED | |
2290 | use extended POSIX syntax | |
2291 | @end defvar | |
2292 | @defvar REG_ICASE | |
2293 | use case-insensitive matching | |
2294 | @end defvar | |
2295 | @defvar REG_NEWLINE | |
2296 | allow anchors to match after newline characters in the | |
2297 | string and prevents @code{.} or @code{[^...]} from matching newlines. | |
2298 | @end defvar | |
2299 | ||
2300 | The @code{logior} procedure can be used to combine multiple flags. | |
2301 | The default is to use | |
2302 | POSIX basic syntax, which makes @code{+} and @code{?} literals and @code{\+} | |
2303 | and @code{\?} | |
2304 | operators. Backslashes in @var{pattern} must be escaped if specified in a | |
2305 | literal string e.g., @code{"\\(a\\)\\?"}. | |
2306 | @end deffn | |
2307 | ||
2308 | @c NJFIXME not in libguile! | |
2309 | @deffn primitive regexec regex string [match-pick] [flags] | |
2310 | ||
2311 | Match @var{string} against the compiled POSIX regular expression | |
2312 | @var{regex}. | |
2313 | @var{match-pick} and @var{flags} are optional. Possible flags (which can be | |
2314 | combined using the logior procedure) are: | |
2315 | ||
2316 | @defvar REG_NOTBOL | |
2317 | The beginning of line operator won't match the beginning of | |
2318 | @var{string} (presumably because it's not the beginning of a line) | |
2319 | @end defvar | |
2320 | ||
2321 | @defvar REG_NOTEOL | |
2322 | Similar to REG_NOTBOL, but prevents the end of line operator | |
2323 | from matching the end of @var{string}. | |
2324 | @end defvar | |
2325 | ||
2326 | If no match is possible, regexec returns #f. Otherwise @var{match-pick} | |
2327 | determines the return value: | |
2328 | ||
2329 | @code{#t} or unspecified: a newly-allocated vector is returned, | |
2330 | containing pairs with the indices of the matched part of @var{string} and any | |
2331 | substrings. | |
2332 | ||
2333 | @code{""}: a list is returned: the first element contains a nested list | |
2334 | with the matched part of @var{string} surrounded by the the unmatched parts. | |
2335 | Remaining elements are matched substrings (if any). All returned | |
2336 | substrings share memory with @var{string}. | |
2337 | ||
2338 | @code{#f}: regexec returns #t if a match is made, otherwise #f. | |
2339 | ||
2340 | vector: the supplied vector is returned, with the first element replaced | |
2341 | by a pair containing the indices of the matched portion of @var{string} and | |
2342 | further elements replaced by pairs containing the indices of matched | |
2343 | substrings (if any). | |
2344 | ||
2345 | list: a list will be returned, with each member of the list | |
2346 | specified by a code in the corresponding position of the supplied list: | |
2347 | ||
2348 | a number: the numbered matching substring (0 for the entire match). | |
2349 | ||
2350 | @code{#\<}: the beginning of @var{string} to the beginning of the part matched | |
2351 | by regex. | |
2352 | ||
2353 | @code{#\>}: the end of the matched part of @var{string} to the end of | |
2354 | @var{string}. | |
2355 | ||
2356 | @code{#\c}: the "final tag", which seems to be associated with the "cut | |
2357 | operator", which doesn't seem to be available through the posix | |
2358 | interface. | |
2359 | ||
2360 | e.g., @code{(list #\< 0 1 #\>)}. The returned substrings share memory with | |
2361 | @var{string}. | |
2362 | @end deffn | |
2363 | ||
2364 | Here are some other procedures that might be used when using regular | |
2365 | expressions: | |
2366 | ||
2367 | @c NJFIXME not in libguile! | |
2368 | @deffn primitive compiled-regexp? obj | |
2369 | Test whether obj is a compiled regular expression. | |
2370 | @end deffn | |
2371 | ||
2372 | @c NJFIXME not in libguile! | |
2373 | @deffn primitive regexp->dfa regex [flags] | |
2374 | @end deffn | |
2375 | ||
2376 | @c NJFIXME not in libguile! | |
2377 | @deffn primitive dfa-fork dfa | |
2378 | @end deffn | |
2379 | ||
2380 | @c NJFIXME not in libguile! | |
2381 | @deffn primitive reset-dfa! dfa | |
2382 | @end deffn | |
2383 | ||
2384 | @c NJFIXME not in libguile! | |
2385 | @deffn primitive dfa-final-tag dfa | |
2386 | @end deffn | |
2387 | ||
2388 | @c NJFIXME not in libguile! | |
2389 | @deffn primitive dfa-continuable? dfa | |
2390 | @end deffn | |
2391 | ||
2392 | @c NJFIXME not in libguile! | |
2393 | @deffn primitive advance-dfa! dfa string | |
2394 | @end deffn | |
2395 | ||
2396 | ||
2397 | @node Symbols and Variables | |
2398 | @section Symbols and Variables | |
fcaedf99 MG |
2399 | @r5index symbol? |
2400 | @r5index symbol->string | |
2401 | @r5index string->symbol | |
2402 | ||
38a93523 NJ |
2403 | |
2404 | Guile symbol tables are hash tables. Each hash table, also called an | |
2405 | @dfn{obarray} (for `object array'), is a vector of association lists. | |
2406 | Each entry in the alists is a pair (@var{SYMBOL} . @var{VALUE}). To | |
2407 | @dfn{intern} a symbol in a symbol table means to return its | |
2408 | (@var{SYMBOL} . @var{VALUE}) pair, adding a new entry to the symbol | |
2409 | table (with an undefined value) if none is yet present. | |
2410 | ||
fcaedf99 MG |
2411 | @c FIXME::martin: According to NEWS, removed. Remove here too, or |
2412 | @c leave for compatibility? | |
2413 | @c @c docstring begin (texi-doc-string "guile" "builtin-bindings") | |
2414 | @c @deffn primitive builtin-bindings | |
2415 | @c Create and return a copy of the global symbol table, removing all | |
2416 | @c unbound symbols. | |
2417 | @c @end deffn | |
38a93523 NJ |
2418 | |
2419 | @c docstring begin (texi-doc-string "guile" "gensym") | |
2420 | @deffn primitive gensym [prefix] | |
2421 | Create a new symbol with a name constructed from a prefix and | |
2422 | a counter value. The string @var{prefix} can be specified as | |
2423 | an optional argument. Default prefix is @code{g}. The counter | |
2424 | is increased by 1 at each call. There is no provision for | |
2425 | resetting the counter. | |
2426 | @end deffn | |
2427 | ||
2428 | @c docstring begin (texi-doc-string "guile" "gentemp") | |
2429 | @deffn primitive gentemp [prefix [obarray]] | |
2430 | Create a new symbol with a name unique in an obarray. | |
2431 | The name is constructed from an optional string @var{prefix} | |
2432 | and a counter value. The default prefix is @code{t}. The | |
2433 | @var{obarray} is specified as a second optional argument. | |
2434 | Default is the system obarray where all normal symbols are | |
2435 | interned. The counter is increased by 1 at each | |
2436 | call. There is no provision for resetting the counter. | |
2437 | @end deffn | |
2438 | ||
2439 | @c docstring begin (texi-doc-string "guile" "intern-symbol") | |
2440 | @deffn primitive intern-symbol obarray string | |
2441 | Add a new symbol to @var{obarray} with name @var{string}, bound to an | |
2442 | unspecified initial value. The symbol table is not modified if a symbol | |
2443 | with this name is already present. | |
2444 | @end deffn | |
2445 | ||
2446 | @c docstring begin (texi-doc-string "guile" "string->obarray-symbol") | |
2447 | @deffn primitive string->obarray-symbol obarray string [soft?] | |
2448 | Intern a new symbol in @var{obarray}, a symbol table, with name | |
2449 | @var{string}. | |
2450 | ||
2451 | If @var{obarray} is @code{#f}, use the default system symbol table. If | |
2452 | @var{obarray} is @code{#t}, the symbol should not be interned in any | |
2453 | symbol table; merely return the pair (@var{symbol} | |
2454 | . @var{#<undefined>}). | |
2455 | ||
2456 | The @var{soft?} argument determines whether new symbol table entries | |
2457 | should be created when the specified symbol is not already present in | |
2458 | @var{obarray}. If @var{soft?} is specified and is a true value, then | |
2459 | new entries should not be added for symbols not already present in the | |
2460 | table; instead, simply return @code{#f}. | |
2461 | @end deffn | |
2462 | ||
2463 | @c docstring begin (texi-doc-string "guile" "string->symbol") | |
2464 | @deffn primitive string->symbol string | |
2465 | Returns the symbol whose name is @var{string}. This procedure can | |
2466 | create symbols with names containing special characters or letters in | |
2467 | the non-standard case, but it is usually a bad idea to create such | |
2468 | symbols because in some implementations of Scheme they cannot be read as | |
780ee65e NJ |
2469 | themselves. See @code{symbol->string}. |
2470 | ||
2471 | The following examples assume that the implementation's | |
2472 | standard case is lower case: | |
2473 | ||
2474 | @lisp | |
2475 | (eq? 'mISSISSIppi 'mississippi) @result{} #t | |
2476 | (string->symbol "mISSISSIppi") @result{} @r{the symbol with name "mISSISSIppi"} | |
2477 | (eq? 'bitBlt (string->symbol "bitBlt")) @result{} #f | |
38a93523 | 2478 | (eq? 'JollyWog |
780ee65e | 2479 | (string->symbol (symbol->string 'JollyWog))) @result{} #t |
38a93523 | 2480 | (string=? "K. Harper, M.D." |
780ee65e NJ |
2481 | (symbol->string |
2482 | (string->symbol "K. Harper, M.D."))) @result{}#t | |
2483 | @end lisp | |
38a93523 NJ |
2484 | @end deffn |
2485 | ||
2486 | @c docstring begin (texi-doc-string "guile" "symbol->string") | |
780ee65e NJ |
2487 | @deffn primitive symbol->string s |
2488 | Returns the name of @var{symbol} as a string. If the symbol | |
2489 | was part of an object returned as the value of a literal | |
2490 | expression (section @pxref{Literal expressions,,,r4rs, The | |
2491 | Revised^4 Report on Scheme}) or by a call to the @code{read} | |
2492 | procedure, and its name contains alphabetic characters, then | |
2493 | the string returned will contain characters in the | |
2494 | implementation's preferred standard case---some implementations | |
2495 | will prefer upper case, others lower case. If the symbol was | |
2496 | returned by @code{string->symbol}, the case of characters in | |
2497 | the string returned will be the same as the case in the string | |
2498 | that was passed to @code{string->symbol}. It is an error to | |
2499 | apply mutation procedures like @code{string-set!} to strings | |
2500 | returned by this procedure. (r5rs) | |
2501 | ||
2502 | The following examples assume that the implementation's | |
2503 | standard case is lower case: | |
2504 | ||
2505 | @lisp | |
2506 | (symbol->string 'flying-fish) @result{} "flying-fish" | |
2507 | (symbol->string 'Martin) @result{} "martin" | |
38a93523 | 2508 | (symbol->string |
780ee65e NJ |
2509 | (string->symbol "Malvina")) @result{} "Malvina" |
2510 | @end lisp | |
38a93523 NJ |
2511 | @end deffn |
2512 | ||
2513 | @c docstring begin (texi-doc-string "guile" "symbol-binding") | |
2514 | @deffn primitive symbol-binding obarray string | |
2515 | Look up in @var{obarray} the symbol whose name is @var{string}, and | |
2516 | return the value to which it is bound. If @var{obarray} is @code{#f}, | |
2517 | use the global symbol table. If @var{string} is not interned in | |
2518 | @var{obarray}, an error is signalled. | |
2519 | @end deffn | |
2520 | ||
2521 | @c docstring begin (texi-doc-string "guile" "symbol-bound?") | |
2522 | @deffn primitive symbol-bound? obarray string | |
780ee65e | 2523 | Return @code{#t} if @var{obarray} contains a symbol with name |
38a93523 | 2524 | @var{string} bound to a defined value. This differs from |
780ee65e NJ |
2525 | @var{symbol-interned?} in that the mere mention of a symbol |
2526 | usually causes it to be interned; @code{symbol-bound?} | |
2527 | determines whether a symbol has been given any meaningful | |
2528 | value. | |
38a93523 NJ |
2529 | @end deffn |
2530 | ||
2531 | @c docstring begin (texi-doc-string "guile" "symbol-fref") | |
2532 | @deffn primitive symbol-fref symbol | |
2533 | Return the contents of @var{symbol}'s @dfn{function slot}. | |
2534 | @end deffn | |
2535 | ||
2536 | @c docstring begin (texi-doc-string "guile" "symbol-fset!") | |
2537 | @deffn primitive symbol-fset! symbol value | |
2538 | Change the binding of @var{symbol}'s function slot. | |
2539 | @end deffn | |
2540 | ||
2541 | @c docstring begin (texi-doc-string "guile" "symbol-hash") | |
2542 | @deffn primitive symbol-hash symbol | |
2543 | Return a hash value for @var{symbol}. | |
2544 | @end deffn | |
2545 | ||
2546 | @c docstring begin (texi-doc-string "guile" "symbol-interned?") | |
2547 | @deffn primitive symbol-interned? obarray string | |
780ee65e NJ |
2548 | Return @code{#t} if @var{obarray} contains a symbol with name |
2549 | @var{string}, and @code{#f} otherwise. | |
38a93523 NJ |
2550 | @end deffn |
2551 | ||
2552 | @c docstring begin (texi-doc-string "guile" "symbol-pref") | |
2553 | @deffn primitive symbol-pref symbol | |
2554 | Return the @dfn{property list} currently associated with @var{symbol}. | |
2555 | @end deffn | |
2556 | ||
2557 | @c docstring begin (texi-doc-string "guile" "symbol-pset!") | |
2558 | @deffn primitive symbol-pset! symbol value | |
2559 | Change the binding of @var{symbol}'s property slot. | |
2560 | @end deffn | |
2561 | ||
2562 | @c docstring begin (texi-doc-string "guile" "symbol-set!") | |
2563 | @deffn primitive symbol-set! obarray string value | |
2564 | Find the symbol in @var{obarray} whose name is @var{string}, and rebind | |
2565 | it to @var{value}. An error is signalled if @var{string} is not present | |
2566 | in @var{obarray}. | |
2567 | @end deffn | |
2568 | ||
2569 | @c docstring begin (texi-doc-string "guile" "symbol?") | |
2570 | @deffn primitive symbol? obj | |
780ee65e NJ |
2571 | Returns @code{#t} if @var{obj} is a symbol, otherwise returns |
2572 | @code{#f}. (r5rs) | |
38a93523 NJ |
2573 | @end deffn |
2574 | ||
2575 | @c docstring begin (texi-doc-string "guile" "unintern-symbol") | |
2576 | @deffn primitive unintern-symbol obarray string | |
2577 | Remove the symbol with name @var{string} from @var{obarray}. This | |
2578 | function returns @code{#t} if the symbol was present and @code{#f} | |
2579 | otherwise. | |
2580 | @end deffn | |
2581 | ||
2582 | @c docstring begin (texi-doc-string "guile" "builtin-variable") | |
2583 | @deffn primitive builtin-variable name | |
2584 | Return the built-in variable with the name @var{name}. | |
2585 | @var{name} must be a symbol (not a string). | |
2586 | Then use @code{variable-ref} to access its value. | |
2587 | @end deffn | |
2588 | ||
2589 | @c docstring begin (texi-doc-string "guile" "make-undefined-variable") | |
2590 | @deffn primitive make-undefined-variable [name-hint] | |
2591 | Return a variable object initialized to an undefined value. | |
2592 | If given, uses @var{name-hint} as its internal (debugging) | |
2593 | name, otherwise just treat it as an anonymous variable. | |
2594 | Remember, of course, that multiple bindings to the same | |
2595 | variable may exist, so @var{name-hint} is just that---a hint. | |
2596 | @end deffn | |
2597 | ||
2598 | @c docstring begin (texi-doc-string "guile" "make-variable") | |
2599 | @deffn primitive make-variable init [name-hint] | |
2600 | Return a variable object initialized to value @var{init}. | |
2601 | If given, uses @var{name-hint} as its internal (debugging) | |
2602 | name, otherwise just treat it as an anonymous variable. | |
2603 | Remember, of course, that multiple bindings to the same | |
2604 | variable may exist, so @var{name-hint} is just that---a hint. | |
2605 | @end deffn | |
2606 | ||
2607 | @c docstring begin (texi-doc-string "guile" "variable-bound?") | |
2608 | @deffn primitive variable-bound? var | |
2609 | Return @code{#t} iff @var{var} is bound to a value. | |
2610 | Throws an error if @var{var} is not a variable object. | |
2611 | @end deffn | |
2612 | ||
2613 | @c docstring begin (texi-doc-string "guile" "variable-ref") | |
2614 | @deffn primitive variable-ref var | |
2615 | Dereference @var{var} and return its value. | |
2616 | @var{var} must be a variable object; see @code{make-variable} | |
2617 | and @code{make-undefined-variable}. | |
2618 | @end deffn | |
2619 | ||
2620 | @c docstring begin (texi-doc-string "guile" "variable-set!") | |
2621 | @deffn primitive variable-set! var val | |
2622 | Set the value of the variable @var{var} to @var{val}. | |
2623 | @var{var} must be a variable object, @var{val} can be any | |
2624 | value. Return an unspecified value. | |
2625 | @end deffn | |
2626 | ||
2627 | @c docstring begin (texi-doc-string "guile" "variable?") | |
2628 | @deffn primitive variable? obj | |
2629 | Return @code{#t} iff @var{obj} is a variable object, else | |
2630 | return @code{#f} | |
2631 | @end deffn | |
2632 | ||
2633 | ||
2634 | @node Keywords | |
2635 | @section Keywords | |
2636 | ||
2637 | Keywords are self-evaluating objects with a convenient read syntax that | |
2638 | makes them easy to type. | |
2639 | ||
2640 | Guile's keyword support conforms to R4RS, and adds a (switchable) read | |
2641 | syntax extension to permit keywords to begin with @code{:} as well as | |
2642 | @code{#:}. | |
2643 | ||
2644 | @menu | |
2645 | * Why Use Keywords?:: | |
2646 | * Coding With Keywords:: | |
2647 | * Keyword Read Syntax:: | |
2648 | * Keyword Primitives:: | |
2649 | @end menu | |
2650 | ||
2651 | @node Why Use Keywords? | |
2652 | @subsection Why Use Keywords? | |
2653 | ||
2654 | Keywords are useful in contexts where a program or procedure wants to be | |
2655 | able to accept a large number of optional arguments without making its | |
2656 | interface unmanageable. | |
2657 | ||
2658 | To illustrate this, consider a hypothetical @code{make-window} | |
2659 | procedure, which creates a new window on the screen for drawing into | |
2660 | using some graphical toolkit. There are many parameters that the caller | |
2661 | might like to specify, but which could also be sensibly defaulted, for | |
2662 | example: | |
2663 | ||
2664 | @itemize @bullet | |
2665 | @item | |
2666 | colour depth -- Default: the colour depth for the screen | |
2667 | ||
2668 | @item | |
2669 | background colour -- Default: white | |
2670 | ||
2671 | @item | |
2672 | width -- Default: 600 | |
2673 | ||
2674 | @item | |
2675 | height -- Default: 400 | |
2676 | @end itemize | |
2677 | ||
2678 | If @code{make-window} did not use keywords, the caller would have to | |
2679 | pass in a value for each possible argument, remembering the correct | |
2680 | argument order and using a special value to indicate the default value | |
2681 | for that argument: | |
2682 | ||
2683 | @lisp | |
2684 | (make-window 'default ;; Colour depth | |
2685 | 'default ;; Background colour | |
2686 | 800 ;; Width | |
2687 | 100 ;; Height | |
2688 | @dots{}) ;; More make-window arguments | |
2689 | @end lisp | |
2690 | ||
2691 | With keywords, on the other hand, defaulted arguments are omitted, and | |
2692 | non-default arguments are clearly tagged by the appropriate keyword. As | |
2693 | a result, the invocation becomes much clearer: | |
2694 | ||
2695 | @lisp | |
2696 | (make-window #:width 800 #:height 100) | |
2697 | @end lisp | |
2698 | ||
2699 | On the other hand, for a simpler procedure with few arguments, the use | |
2700 | of keywords would be a hindrance rather than a help. The primitive | |
2701 | procedure @code{cons}, for example, would not be improved if it had to | |
2702 | be invoked as | |
2703 | ||
2704 | @lisp | |
2705 | (cons #:car x #:cdr y) | |
2706 | @end lisp | |
2707 | ||
2708 | So the decision whether to use keywords or not is purely pragmatic: use | |
2709 | them if they will clarify the procedure invocation at point of call. | |
2710 | ||
2711 | @node Coding With Keywords | |
2712 | @subsection Coding With Keywords | |
2713 | ||
2714 | If a procedure wants to support keywords, it should take a rest argument | |
2715 | and then use whatever means is convenient to extract keywords and their | |
2716 | corresponding arguments from the contents of that rest argument. | |
2717 | ||
2718 | The following example illustrates the principle: the code for | |
2719 | @code{make-window} uses a helper procedure called | |
2720 | @code{get-keyword-value} to extract individual keyword arguments from | |
2721 | the rest argument. | |
2722 | ||
2723 | @lisp | |
2724 | (define (get-keyword-value args keyword default) | |
2725 | (let ((kv (memq keyword args))) | |
2726 | (if (and kv (>= (length kv) 2)) | |
2727 | (cadr kv) | |
2728 | default))) | |
2729 | ||
2730 | (define (make-window . args) | |
2731 | (let ((depth (get-keyword-value args #:depth screen-depth)) | |
2732 | (bg (get-keyword-value args #:bg "white")) | |
2733 | (width (get-keyword-value args #:width 800)) | |
2734 | (height (get-keyword-value args #:height 100)) | |
2735 | @dots{}) | |
2736 | @dots{})) | |
2737 | @end lisp | |
2738 | ||
2739 | But you don't need to write @code{get-keyword-value}. The @code{(ice-9 | |
2740 | optargs)} module provides a set of powerful macros that you can use to | |
2741 | implement keyword-supporting procedures like this: | |
2742 | ||
2743 | @lisp | |
2744 | (use-modules (ice-9 optargs)) | |
2745 | ||
2746 | (define (make-window . args) | |
2747 | (let-keywords args #f ((depth screen-depth) | |
2748 | (bg "white") | |
2749 | (width 800) | |
2750 | (height 100)) | |
2751 | ...)) | |
2752 | @end lisp | |
2753 | ||
2754 | @noindent | |
2755 | Or, even more economically, like this: | |
2756 | ||
2757 | @lisp | |
2758 | (use-modules (ice-9 optargs)) | |
2759 | ||
2760 | (define* (make-window #:key (depth screen-depth) | |
2761 | (bg "white") | |
2762 | (width 800) | |
2763 | (height 100)) | |
2764 | ...) | |
2765 | @end lisp | |
2766 | ||
2767 | For further details on @code{let-keywords}, @code{define*} and other | |
2768 | facilities provided by the @code{(ice-9 optargs)} module, @ref{Optional | |
2769 | Arguments}. | |
2770 | ||
2771 | ||
2772 | @node Keyword Read Syntax | |
2773 | @subsection Keyword Read Syntax | |
2774 | ||
2775 | Guile, by default, only recognizes the keyword syntax specified by R5RS. | |
2776 | A token of the form @code{#:NAME}, where @code{NAME} has the same syntax | |
2777 | as a Scheme symbol, is the external representation of the keyword named | |
2778 | @code{NAME}. Keyword objects print using this syntax as well, so values | |
2779 | containing keyword objects can be read back into Guile. When used in an | |
2780 | expression, keywords are self-quoting objects. | |
2781 | ||
2782 | If the @code{keyword} read option is set to @code{'prefix}, Guile also | |
2783 | recognizes the alternative read syntax @code{:NAME}. Otherwise, tokens | |
2784 | of the form @code{:NAME} are read as symbols, as required by R4RS. | |
2785 | ||
2786 | To enable and disable the alternative non-R4RS keyword syntax, you use | |
2787 | the @code{read-options} procedure documented in @ref{General option | |
2788 | interface} and @ref{Reader options}. | |
2789 | ||
2790 | @smalllisp | |
2791 | (read-set! keywords 'prefix) | |
2792 | ||
2793 | #:type | |
2794 | @result{} | |
2795 | #:type | |
2796 | ||
2797 | :type | |
2798 | @result{} | |
2799 | #:type | |
2800 | ||
2801 | (read-set! keywords #f) | |
2802 | ||
2803 | #:type | |
2804 | @result{} | |
2805 | #:type | |
2806 | ||
2807 | :type | |
2808 | @result{} | |
2809 | ERROR: In expression :type: | |
2810 | ERROR: Unbound variable: :type | |
2811 | ABORT: (unbound-variable) | |
2812 | @end smalllisp | |
2813 | ||
2814 | @node Keyword Primitives | |
2815 | @subsection Keyword Primitives | |
2816 | ||
2817 | Internally, a keyword is implemented as something like a tagged symbol, | |
2818 | where the tag identifies the keyword as being self-evaluating, and the | |
2819 | symbol, known as the keyword's @dfn{dash symbol} has the same name as | |
2820 | the keyword name but prefixed by a single dash. For example, the | |
2821 | keyword @code{#:name} has the corresponding dash symbol @code{-name}. | |
2822 | ||
2823 | Most keyword objects are constructed automatically by the reader when it | |
2824 | reads a token beginning with @code{#:}. However, if you need to | |
2825 | construct a keyword object programmatically, you can do so by calling | |
2826 | @code{make-keyword-from-dash-symbol} with the corresponding dash symbol | |
2827 | (as the reader does). The dash symbol for a keyword object can be | |
2828 | retrieved using the @code{keyword-dash-symbol} procedure. | |
2829 | ||
2830 | @c docstring begin (texi-doc-string "guile" "make-keyword-from-dash-symbol") | |
2831 | @deffn primitive make-keyword-from-dash-symbol symbol | |
2832 | Make a keyword object from a @var{symbol} that starts with a dash. | |
2833 | @end deffn | |
2834 | ||
2835 | @c docstring begin (texi-doc-string "guile" "keyword?") | |
2836 | @deffn primitive keyword? obj | |
2837 | Returns @code{#t} if the argument @var{obj} is a keyword, else @code{#f}. | |
2838 | @end deffn | |
2839 | ||
2840 | @c docstring begin (texi-doc-string "guile" "keyword-dash-symbol") | |
2841 | @deffn primitive keyword-dash-symbol keyword | |
2842 | Return the dash symbol for @var{keyword}. | |
2843 | This is the inverse of @code{make-keyword-from-dash-symbol}. | |
2844 | @end deffn | |
2845 | ||
2846 | ||
2847 | @node Pairs | |
2848 | @section Pairs | |
fcaedf99 MG |
2849 | @r5index pair? |
2850 | @r5index cons | |
2851 | @r5index set-car! | |
2852 | @r5index set-cdr! | |
38a93523 NJ |
2853 | |
2854 | @c docstring begin (texi-doc-string "guile" "cons") | |
2855 | @deffn primitive cons x y | |
2856 | Returns a newly allocated pair whose car is @var{x} and whose cdr is | |
2857 | @var{y}. The pair is guaranteed to be different (in the sense of | |
2858 | @code{eqv?}) from every previously existing object. | |
2859 | @end deffn | |
2860 | ||
2861 | @c docstring begin (texi-doc-string "guile" "pair?") | |
2862 | @deffn primitive pair? x | |
2863 | Returns @code{#t} if @var{x} is a pair; otherwise returns @code{#f}. | |
2864 | @end deffn | |
2865 | ||
fcaedf99 MG |
2866 | @r5index car |
2867 | @r5index cdr | |
2868 | @deffn primitive car pair | |
2869 | @deffnx primitive cdr pair | |
2870 | Return the car or the cdr of @var{pair}, respectively. | |
2871 | @end deffn | |
2872 | ||
2873 | @deffn primitive caar pair | |
2874 | @deffnx primitive cadr pair @dots{} | |
2875 | @deffnx primitive cdddar pair | |
2876 | @deffnx primitive cddddr pair | |
2877 | These procedures are compositions of @code{car} and @code{cdr}, where | |
2878 | for example @code{caddr} could be defined by | |
2879 | ||
2880 | @lisp | |
2881 | (define caddr (lambda (x) (car (cdr (cdr x))))) | |
2882 | @end lisp | |
2883 | @end deffn | |
2884 | ||
38a93523 NJ |
2885 | @c docstring begin (texi-doc-string "guile" "set-car!") |
2886 | @deffn primitive set-car! pair value | |
2887 | Stores @var{value} in the car field of @var{pair}. The value returned | |
2888 | by @code{set-car!} is unspecified. | |
2889 | @end deffn | |
2890 | ||
2891 | @c docstring begin (texi-doc-string "guile" "set-cdr!") | |
2892 | @deffn primitive set-cdr! pair value | |
2893 | Stores @var{value} in the cdr field of @var{pair}. The value returned | |
2894 | by @code{set-cdr!} is unspecified. | |
2895 | @end deffn | |
2896 | ||
2897 | ||
2898 | @node Lists | |
2899 | @section Lists | |
fcaedf99 MG |
2900 | @r5index null? |
2901 | @r5index list? | |
2902 | @r5index list | |
2903 | @r5index length | |
2904 | @r5index append | |
2905 | @r5index reverse | |
2906 | @r5index list-tail | |
2907 | @r5index list-ref | |
2908 | @r5index memq | |
2909 | @r5index memv | |
2910 | @r5index member | |
2911 | ||
38a93523 NJ |
2912 | |
2913 | @c docstring begin (texi-doc-string "guile" "list") | |
2914 | @deffn primitive list . objs | |
780ee65e NJ |
2915 | Return a list containing @var{objs}, the arguments to |
2916 | @code{list}. | |
38a93523 NJ |
2917 | @end deffn |
2918 | ||
2919 | @c docstring begin (texi-doc-string "guile" "cons*") | |
2920 | @deffn primitive cons* arg . rest | |
780ee65e NJ |
2921 | Like @code{list}, but the last arg provides the tail of the |
2922 | constructed list, returning @code{(cons @var{arg1} (cons | |
2923 | @var{arg2} (cons @dots{} @var{argn}))). Requires at least one | |
2924 | argument. If given one argument, that argument is returned as | |
2925 | result. This function is called @code{list*} in some other | |
2926 | Schemes and in Common LISP. | |
38a93523 NJ |
2927 | @end deffn |
2928 | ||
2929 | @c docstring begin (texi-doc-string "guile" "list?") | |
2930 | @deffn primitive list? x | |
780ee65e | 2931 | Return @code{#t} iff @var{x} is a proper list, else @code{#f}. |
38a93523 NJ |
2932 | @end deffn |
2933 | ||
2934 | @c docstring begin (texi-doc-string "guile" "null?") | |
2935 | @deffn primitive null? x | |
780ee65e | 2936 | Return @code{#t} iff @var{x} is the empty list, else @code{#f}. |
38a93523 NJ |
2937 | @end deffn |
2938 | ||
2939 | @c docstring begin (texi-doc-string "guile" "length") | |
2940 | @deffn primitive length lst | |
780ee65e | 2941 | Return the number of elements in list @var{lst}. |
38a93523 NJ |
2942 | @end deffn |
2943 | ||
2944 | @c docstring begin (texi-doc-string "guile" "append") | |
2945 | @deffn primitive append . args | |
780ee65e NJ |
2946 | Return a list consisting of the elements the lists passed as |
2947 | arguments. | |
38a93523 | 2948 | @example |
780ee65e NJ |
2949 | (append '(x) '(y)) @result{} (x y) |
2950 | (append '(a) '(b c d)) @result{} (a b c d) | |
2951 | (append '(a (b)) '((c))) @result{} (a (b) (c)) | |
38a93523 | 2952 | @end example |
780ee65e NJ |
2953 | The resulting list is always newly allocated, except that it |
2954 | shares structure with the last list argument. The last | |
2955 | argument may actually be any object; an improper list results | |
2956 | if the last argument is not a proper list. | |
38a93523 | 2957 | @example |
780ee65e NJ |
2958 | (append '(a b) '(c . d)) @result{} (a b c . d) |
2959 | (append '() 'a) @result{} a | |
38a93523 NJ |
2960 | @end example |
2961 | @end deffn | |
2962 | ||
2963 | @c ARGFIXME args ? | |
2964 | @c docstring begin (texi-doc-string "guile" "append!") | |
2965 | @deffn primitive append! . args | |
2966 | A destructive version of @code{append} (@pxref{Pairs and Lists,,,r4rs, | |
2967 | The Revised^4 Report on Scheme}). The cdr field of each list's final | |
2968 | pair is changed to point to the head of the next list, so no consing is | |
2969 | performed. Return a pointer to the mutated list. | |
2970 | @end deffn | |
2971 | ||
2972 | @c docstring begin (texi-doc-string "guile" "last-pair") | |
2973 | @deffn primitive last-pair lst | |
2974 | Return a pointer to the last pair in @var{lst}, signalling an error if | |
2975 | @var{lst} is circular. | |
2976 | @end deffn | |
2977 | ||
2978 | @c docstring begin (texi-doc-string "guile" "reverse") | |
2979 | @deffn primitive reverse lst | |
780ee65e NJ |
2980 | Return a new list that contains the elements of @var{lst} but |
2981 | in reverse order. | |
38a93523 NJ |
2982 | @end deffn |
2983 | ||
2984 | @c NJFIXME explain new_tail | |
2985 | @c docstring begin (texi-doc-string "guile" "reverse!") | |
2986 | @deffn primitive reverse! lst [new_tail] | |
2987 | A destructive version of @code{reverse} (@pxref{Pairs and Lists,,,r4rs, | |
2988 | The Revised^4 Report on Scheme}). The cdr of each cell in @var{lst} is | |
2989 | modified to point to the previous list element. Return a pointer to the | |
2990 | head of the reversed list. | |
2991 | ||
2992 | Caveat: because the list is modified in place, the tail of the original | |
2993 | list now becomes its head, and the head of the original list now becomes | |
2994 | the tail. Therefore, the @var{lst} symbol to which the head of the | |
2995 | original list was bound now points to the tail. To ensure that the head | |
2996 | of the modified list is not lost, it is wise to save the return value of | |
2997 | @code{reverse!} | |
2998 | @end deffn | |
2999 | ||
3000 | @c docstring begin (texi-doc-string "guile" "list-ref") | |
3001 | @deffn primitive list-ref list k | |
780ee65e | 3002 | Return the @var{k}th element from @var{list}. |
38a93523 NJ |
3003 | @end deffn |
3004 | ||
3005 | @c docstring begin (texi-doc-string "guile" "list-set!") | |
3006 | @deffn primitive list-set! list k val | |
3007 | Set the @var{k}th element of @var{list} to @var{val}. | |
3008 | @end deffn | |
3009 | ||
3010 | @c docstring begin (texi-doc-string "guile" "list-tail") | |
3011 | @c docstring begin (texi-doc-string "guile" "list-cdr-ref") | |
3012 | @deffn primitive list-tail lst k | |
3013 | @deffnx primitive list-cdr-ref lst k | |
3014 | Return the "tail" of @var{lst} beginning with its @var{k}th element. | |
3015 | The first element of the list is considered to be element 0. | |
3016 | ||
3017 | @code{list-tail} and @code{list-cdr-ref} are identical. It may help to | |
3018 | think of @code{list-cdr-ref} as accessing the @var{k}th cdr of the list, | |
3019 | or returning the results of cdring @var{k} times down @var{lst}. | |
3020 | @end deffn | |
3021 | ||
3022 | @c docstring begin (texi-doc-string "guile" "list-cdr-set!") | |
3023 | @deffn primitive list-cdr-set! list k val | |
3024 | Set the @var{k}th cdr of @var{list} to @var{val}. | |
3025 | @end deffn | |
3026 | ||
3027 | @c docstring begin (texi-doc-string "guile" "list-head") | |
3028 | @deffn primitive list-head lst k | |
3029 | Copy the first @var{k} elements from @var{lst} into a new list, and | |
3030 | return it. | |
3031 | @end deffn | |
3032 | ||
3033 | @c docstring begin (texi-doc-string "guile" "list-copy") | |
3034 | @deffn primitive list-copy lst | |
3035 | Return a (newly-created) copy of @var{lst}. | |
3036 | @end deffn | |
3037 | ||
3038 | @c docstring begin (texi-doc-string "guile" "memq") | |
3039 | @deffn primitive memq x lst | |
780ee65e NJ |
3040 | Return the first sublist of @var{lst} whose car is @code{eq?} |
3041 | to @var{x} where the sublists of @var{lst} are the non-empty | |
3042 | lists returned by @code{(list-tail @var{lst} @var{k})} for | |
3043 | @var{k} less than the length of @var{lst}. If @var{x} does not | |
3044 | occur in @var{lst}, then @code{#f} (not the empty list) is | |
38a93523 NJ |
3045 | returned. |
3046 | @end deffn | |
3047 | ||
3048 | @c docstring begin (texi-doc-string "guile" "memv") | |
3049 | @deffn primitive memv x lst | |
780ee65e NJ |
3050 | Return the first sublist of @var{lst} whose car is @code{eqv?} |
3051 | to @var{x} where the sublists of @var{lst} are the non-empty | |
3052 | lists returned by @code{(list-tail @var{lst} @var{k})} for | |
3053 | @var{k} less than the length of @var{lst}. If @var{x} does not | |
3054 | occur in @var{lst}, then @code{#f} (not the empty list) is | |
38a93523 NJ |
3055 | returned. |
3056 | @end deffn | |
3057 | ||
3058 | @c docstring begin (texi-doc-string "guile" "member") | |
3059 | @deffn primitive member x lst | |
780ee65e NJ |
3060 | Return the first sublist of @var{lst} whose car is |
3061 | @code{equal?} to @var{x} where the sublists of @var{lst} are | |
3062 | the non-empty lists returned by @code{(list-tail @var{lst} | |
3063 | @var{k})} for @var{k} less than the length of @var{lst}. If | |
3064 | @var{x} does not occur in @var{lst}, then @code{#f} (not the | |
3065 | empty list) is returned. | |
38a93523 NJ |
3066 | @end deffn |
3067 | ||
3068 | @c docstring begin (texi-doc-string "guile" "delq") | |
3069 | @deffn primitive delq item lst | |
780ee65e NJ |
3070 | Return a newly-created copy of @var{lst} with elements |
3071 | @code{eq?} to @var{item} removed. This procedure mirrors | |
3072 | @code{memq}: @code{delq} compares elements of @var{lst} against | |
3073 | @var{item} with @code{eq?}. | |
38a93523 NJ |
3074 | @end deffn |
3075 | ||
3076 | @c docstring begin (texi-doc-string "guile" "delv") | |
3077 | @deffn primitive delv item lst | |
780ee65e NJ |
3078 | Return a newly-created copy of @var{lst} with elements |
3079 | @code{eqv?} to @var{item} removed. This procedure mirrors | |
3080 | @code{memv}: @code{delv} compares elements of @var{lst} against | |
3081 | @var{item} with @code{eqv?}. | |
38a93523 NJ |
3082 | @end deffn |
3083 | ||
3084 | @c docstring begin (texi-doc-string "guile" "delete") | |
3085 | @deffn primitive delete item lst | |
780ee65e NJ |
3086 | Return a newly-created copy of @var{lst} with elements |
3087 | @code{equal?} to @var{item} removed. This procedure mirrors | |
3088 | @code{member}: @code{delete} compares elements of @var{lst} | |
3089 | against @var{item} with @code{equal?}. | |
38a93523 NJ |
3090 | @end deffn |
3091 | ||
3092 | @c docstring begin (texi-doc-string "guile" "delq!") | |
3093 | @c docstring begin (texi-doc-string "guile" "delv!") | |
3094 | @c docstring begin (texi-doc-string "guile" "delete!") | |
3095 | @deffn primitive delq! item lst | |
3096 | @deffnx primitive delv! item lst | |
3097 | @deffnx primitive delete! item lst | |
3098 | These procedures are destructive versions of @code{delq}, @code{delv} | |
3099 | and @code{delete}: they modify the pointers in the existing @var{lst} | |
3100 | rather than creating a new list. Caveat evaluator: Like other | |
3101 | destructive list functions, these functions cannot modify the binding of | |
3102 | @var{lst}, and so cannot be used to delete the first element of | |
3103 | @var{lst} destructively. | |
3104 | @end deffn | |
3105 | ||
3106 | @c docstring begin (texi-doc-string "guile" "delq1!") | |
3107 | @deffn primitive delq1! item lst | |
780ee65e NJ |
3108 | Like @code{delq!}, but only deletes the first occurrence of |
3109 | @var{item} from @var{lst}. Tests for equality using | |
3110 | @code{eq?}. See also @code{delv1!} and @code{delete1!}. | |
38a93523 NJ |
3111 | @end deffn |
3112 | ||
3113 | @c docstring begin (texi-doc-string "guile" "delv1!") | |
3114 | @deffn primitive delv1! item lst | |
780ee65e NJ |
3115 | Like @code{delv!}, but only deletes the first occurrence of |
3116 | @var{item} from @var{lst}. Tests for equality using | |
3117 | @code{eqv?}. See also @code{delq1!} and @code{delete1!}. | |
38a93523 NJ |
3118 | @end deffn |
3119 | ||
3120 | @c docstring begin (texi-doc-string "guile" "delete1!") | |
3121 | @deffn primitive delete1! item lst | |
780ee65e NJ |
3122 | Like @code{delete!}, but only deletes the first occurrence of |
3123 | @var{item} from @var{lst}. Tests for equality using | |
3124 | @code{equal?}. See also @code{delq1!} and @code{delv1!}. | |
38a93523 NJ |
3125 | @end deffn |
3126 | ||
3127 | [FIXME: is there any reason to have the `sloppy' functions available at | |
3128 | high level at all? Maybe these docs should be relegated to a "Guile | |
3129 | Internals" node or something. -twp] | |
3130 | ||
3131 | @c docstring begin (texi-doc-string "guile" "sloppy-memq") | |
3132 | @deffn primitive sloppy-memq x lst | |
3133 | This procedure behaves like @code{memq}, but does no type or error checking. | |
3134 | Its use is recommended only in writing Guile internals, | |
3135 | not for high-level Scheme programs. | |
3136 | @end deffn | |
3137 | ||
3138 | @c docstring begin (texi-doc-string "guile" "sloppy-memv") | |
3139 | @deffn primitive sloppy-memv x lst | |
3140 | This procedure behaves like @code{memv}, but does no type or error checking. | |
3141 | Its use is recommended only in writing Guile internals, | |
3142 | not for high-level Scheme programs. | |
3143 | @end deffn | |
3144 | ||
3145 | @c docstring begin (texi-doc-string "guile" "sloppy-member") | |
3146 | @deffn primitive sloppy-member x lst | |
3147 | This procedure behaves like @code{member}, but does no type or error checking. | |
3148 | Its use is recommended only in writing Guile internals, | |
3149 | not for high-level Scheme programs. | |
3150 | @end deffn | |
3151 | ||
fcaedf99 | 3152 | @r5index map |
38a93523 NJ |
3153 | @c begin (texi-doc-string "guile" "map") |
3154 | @c docstring begin (texi-doc-string "guile" "map-in-order") | |
3155 | @deffn primitive map proc arg1 . args | |
3156 | @deffnx primitive map-in-order proc arg1 . args | |
3157 | @end deffn | |
3158 | ||
fcaedf99 | 3159 | @r5index for-each |
38a93523 NJ |
3160 | @c begin (texi-doc-string "guile" "for-each") |
3161 | @deffn primitive for-each proc arg1 . args | |
3162 | @end deffn | |
3163 | ||
3164 | ||
3165 | @node Records | |
3166 | @section Records | |
3167 | ||
3168 | [FIXME: this is pasted in from Tom Lord's original guile.texi and should | |
3169 | be reviewed] | |
3170 | ||
3171 | A @dfn{record type} is a first class object representing a user-defined | |
3172 | data type. A @dfn{record} is an instance of a record type. | |
3173 | ||
3174 | @deffn procedure record? obj | |
3175 | Returns @code{#t} if @var{obj} is a record of any type and @code{#f} | |
3176 | otherwise. | |
3177 | ||
3178 | Note that @code{record?} may be true of any Scheme value; there is no | |
3179 | promise that records are disjoint with other Scheme types. | |
3180 | @end deffn | |
3181 | ||
3182 | @deffn procedure make-record-type type-name field-names | |
3183 | Returns a @dfn{record-type descriptor}, a value representing a new data | |
3184 | type disjoint from all others. The @var{type-name} argument must be a | |
3185 | string, but is only used for debugging purposes (such as the printed | |
3186 | representation of a record of the new type). The @var{field-names} | |
3187 | argument is a list of symbols naming the @dfn{fields} of a record of the | |
3188 | new type. It is an error if the list contains any duplicates. It is | |
3189 | unspecified how record-type descriptors are represented.@refill | |
3190 | @end deffn | |
3191 | ||
3192 | @deffn procedure record-constructor rtd [field-names] | |
3193 | Returns a procedure for constructing new members of the type represented | |
3194 | by @var{rtd}. The returned procedure accepts exactly as many arguments | |
3195 | as there are symbols in the given list, @var{field-names}; these are | |
3196 | used, in order, as the initial values of those fields in a new record, | |
3197 | which is returned by the constructor procedure. The values of any | |
3198 | fields not named in that list are unspecified. The @var{field-names} | |
3199 | argument defaults to the list of field names in the call to | |
3200 | @code{make-record-type} that created the type represented by @var{rtd}; | |
3201 | if the @var{field-names} argument is provided, it is an error if it | |
3202 | contains any duplicates or any symbols not in the default list.@refill | |
3203 | @end deffn | |
3204 | ||
3205 | @deffn procedure record-predicate rtd | |
3206 | Returns a procedure for testing membership in the type represented by | |
3207 | @var{rtd}. The returned procedure accepts exactly one argument and | |
3208 | returns a true value if the argument is a member of the indicated record | |
3209 | type; it returns a false value otherwise.@refill | |
3210 | @end deffn | |
3211 | ||
3212 | @deffn procedure record-accessor rtd field-name | |
3213 | Returns a procedure for reading the value of a particular field of a | |
3214 | member of the type represented by @var{rtd}. The returned procedure | |
3215 | accepts exactly one argument which must be a record of the appropriate | |
3216 | type; it returns the current value of the field named by the symbol | |
3217 | @var{field-name} in that record. The symbol @var{field-name} must be a | |
3218 | member of the list of field-names in the call to @code{make-record-type} | |
3219 | that created the type represented by @var{rtd}.@refill | |
3220 | @end deffn | |
3221 | ||
3222 | @deffn procedure record-modifier rtd field-name | |
3223 | Returns a procedure for writing the value of a particular field of a | |
3224 | member of the type represented by @var{rtd}. The returned procedure | |
3225 | accepts exactly two arguments: first, a record of the appropriate type, | |
3226 | and second, an arbitrary Scheme value; it modifies the field named by | |
3227 | the symbol @var{field-name} in that record to contain the given value. | |
3228 | The returned value of the modifier procedure is unspecified. The symbol | |
3229 | @var{field-name} must be a member of the list of field-names in the call | |
3230 | to @code{make-record-type} that created the type represented by | |
3231 | @var{rtd}.@refill | |
3232 | @end deffn | |
3233 | ||
3234 | @deffn procedure record-type-descriptor record | |
3235 | Returns a record-type descriptor representing the type of the given | |
3236 | record. That is, for example, if the returned descriptor were passed to | |
3237 | @code{record-predicate}, the resulting predicate would return a true | |
3238 | value when passed the given record. Note that it is not necessarily the | |
3239 | case that the returned descriptor is the one that was passed to | |
3240 | @code{record-constructor} in the call that created the constructor | |
3241 | procedure that created the given record.@refill | |
3242 | @end deffn | |
3243 | ||
3244 | @deffn procedure record-type-name rtd | |
3245 | Returns the type-name associated with the type represented by rtd. The | |
3246 | returned value is @code{eqv?} to the @var{type-name} argument given in | |
3247 | the call to @code{make-record-type} that created the type represented by | |
3248 | @var{rtd}.@refill | |
3249 | @end deffn | |
3250 | ||
3251 | @deffn procedure record-type-fields rtd | |
3252 | Returns a list of the symbols naming the fields in members of the type | |
3253 | represented by @var{rtd}. The returned value is @code{equal?} to the | |
3254 | field-names argument given in the call to @code{make-record-type} that | |
3255 | created the type represented by @var{rtd}.@refill | |
3256 | @end deffn | |
3257 | ||
3258 | ||
3259 | @node Structures | |
3260 | @section Structures | |
3261 | ||
3262 | [FIXME: this is pasted in from Tom Lord's original guile.texi and should | |
3263 | be reviewed] | |
3264 | ||
3265 | A @dfn{structure type} is a first class user-defined data type. A | |
3266 | @dfn{structure} is an instance of a structure type. A structure type is | |
3267 | itself a structure. | |
3268 | ||
3269 | Structures are less abstract and more general than traditional records. | |
3270 | In fact, in Guile Scheme, records are implemented using structures. | |
3271 | ||
3272 | @menu | |
3273 | * Structure Concepts:: The structure of Structures | |
3274 | * Structure Layout:: Defining the layout of structure types | |
3275 | * Structure Basics:: make-, -ref and -set! procedures for structs | |
3276 | * Vtables:: Accessing type-specific data | |
3277 | @end menu | |
3278 | ||
3279 | @node Structure Concepts | |
3280 | @subsection Structure Concepts | |
3281 | ||
3282 | A structure object consists of a handle, structure data, and a vtable. | |
3283 | The handle is a Scheme value which points to both the vtable and the | |
3284 | structure's data. Structure data is a dynamically allocated region of | |
3285 | memory, private to the structure, divided up into typed fields. A | |
3286 | vtable is another structure used to hold type-specific data. Multiple | |
3287 | structures can share a common vtable. | |
3288 | ||
3289 | Three concepts are key to understanding structures. | |
3290 | ||
3291 | @itemize @bullet{} | |
3292 | @item @dfn{layout specifications} | |
3293 | ||
3294 | Layout specifications determine how memory allocated to structures is | |
3295 | divided up into fields. Programmers must write a layout specification | |
3296 | whenever a new type of structure is defined. | |
3297 | ||
3298 | @item @dfn{structural accessors} | |
3299 | ||
3300 | Structure access is by field number. There is only one set of | |
3301 | accessors common to all structure objects. | |
3302 | ||
3303 | @item @dfn{vtables} | |
3304 | ||
3305 | Vtables, themselves structures, are first class representations of | |
3306 | disjoint sub-types of structures in general. In most cases, when a | |
3307 | new structure is created, programmers must specifiy a vtable for the | |
3308 | new structure. Each vtable has a field describing the layout of its | |
3309 | instances. Vtables can have additional, user-defined fields as well. | |
3310 | @end itemize | |
3311 | ||
3312 | ||
3313 | ||
3314 | @node Structure Layout | |
3315 | @subsection Structure Layout | |
3316 | ||
3317 | When a structure is created, a region of memory is allocated to hold its | |
3318 | state. The @dfn{layout} of the structure's type determines how that | |
3319 | memory is divided into fields. | |
3320 | ||
3321 | Each field has a specified type. There are only three types allowed, each | |
3322 | corresponding to a one letter code. The allowed types are: | |
3323 | ||
3324 | @itemize @bullet{} | |
3325 | @item 'u' -- unprotected | |
3326 | ||
3327 | The field holds binary data that is not GC protected. | |
3328 | ||
3329 | @item 'p' -- protected | |
3330 | ||
3331 | The field holds a Scheme value and is GC protected. | |
3332 | ||
3333 | @item 's' -- self | |
3334 | ||
3335 | The field holds a Scheme value and is GC protected. When a structure is | |
3336 | created with this type of field, the field is initialized to refer to | |
3337 | the structure's own handle. This kind of field is mainly useful when | |
3338 | mixing Scheme and C code in which the C code may need to compute a | |
3339 | structure's handle given only the address of its malloced data. | |
3340 | @end itemize | |
3341 | ||
3342 | ||
3343 | Each field also has an associated access protection. There are only | |
3344 | three kinds of protection, each corresponding to a one letter code. | |
3345 | The allowed protections are: | |
3346 | ||
3347 | @itemize @bullet{} | |
3348 | @item 'w' -- writable | |
3349 | ||
3350 | The field can be read and written. | |
3351 | ||
3352 | @item 'r' -- readable | |
3353 | ||
3354 | The field can be read, but not written. | |
3355 | ||
3356 | @item 'o' -- opaque | |
3357 | ||
3358 | The field can be neither read nor written. This kind | |
3359 | of protection is for fields useful only to built-in routines. | |
3360 | @end itemize | |
3361 | ||
3362 | A layout specification is described by stringing together pairs | |
3363 | of letters: one to specify a field type and one to specify a field | |
3364 | protection. For example, a traditional cons pair type object could | |
3365 | be described as: | |
3366 | ||
3367 | @example | |
3368 | ; cons pairs have two writable fields of Scheme data | |
3369 | "pwpw" | |
3370 | @end example | |
3371 | ||
3372 | A pair object in which the first field is held constant could be: | |
3373 | ||
3374 | @example | |
3375 | "prpw" | |
3376 | @end example | |
3377 | ||
3378 | Binary fields, (fields of type "u"), hold one @emph{word} each. The | |
3379 | size of a word is a machine dependent value defined to be equal to the | |
3380 | value of the C expression: @code{sizeof (long)}. | |
3381 | ||
3382 | The last field of a structure layout may specify a tail array. | |
3383 | A tail array is indicated by capitalizing the field's protection | |
3384 | code ('W', 'R' or 'O'). A tail-array field is replaced by | |
3385 | a read-only binary data field containing an array size. The array | |
3386 | size is determined at the time the structure is created. It is followed | |
3387 | by a corresponding number of fields of the type specified for the | |
3388 | tail array. For example, a conventional Scheme vector can be | |
3389 | described as: | |
3390 | ||
3391 | @example | |
3392 | ; A vector is an arbitrary number of writable fields holding Scheme | |
3393 | ; values: | |
3394 | "pW" | |
3395 | @end example | |
3396 | ||
3397 | In the above example, field 0 contains the size of the vector and | |
3398 | fields beginning at 1 contain the vector elements. | |
3399 | ||
3400 | A kind of tagged vector (a constant tag followed by conventioal | |
3401 | vector elements) might be: | |
3402 | ||
3403 | @example | |
3404 | "prpW" | |
3405 | @end example | |
3406 | ||
3407 | ||
3408 | Structure layouts are represented by specially interned symbols whose | |
3409 | name is a string of type and protection codes. To create a new | |
3410 | structure layout, use this procedure: | |
3411 | ||
3412 | @c docstring begin (texi-doc-string "guile" "make-struct-layout") | |
3413 | @deffn primitive make-struct-layout fields | |
3414 | Return a new structure layout object. | |
3415 | ||
3416 | @var{fields} must be a string made up of pairs of characters | |
3417 | strung together. The first character of each pair describes a field | |
3418 | type, the second a field protection. Allowed types are 'p' for | |
3419 | GC-protected Scheme data, 'u' for unprotected binary data, and 's' for | |
3420 | a field that points to the structure itself. Allowed protections | |
3421 | are 'w' for mutable fields, 'r' for read-only fields, and 'o' for opaque | |
3422 | fields. The last field protection specification may be capitalized to | |
3423 | indicate that the field is a tail-array. | |
3424 | @end deffn | |
3425 | ||
3426 | ||
3427 | ||
3428 | @node Structure Basics | |
3429 | @subsection Structure Basics | |
3430 | ||
3431 | This section describes the basic procedures for creating and accessing | |
3432 | structures. | |
3433 | ||
3434 | @c docstring begin (texi-doc-string "guile" "make-struct") | |
3435 | @deffn primitive make-struct vtable tail_array_size . init | |
3436 | Create a new structure. | |
3437 | ||
3438 | @var{type} must be a vtable structure (@pxref{Vtables}). | |
3439 | ||
3440 | @var{tail-elts} must be a non-negative integer. If the layout | |
3441 | specification indicated by @var{type} includes a tail-array, | |
3442 | this is the number of elements allocated to that array. | |
3443 | ||
3444 | The @var{init1}, @dots{} are optional arguments describing how | |
3445 | successive fields of the structure should be initialized. Only fields | |
3446 | with protection 'r' or 'w' can be initialized, except for fields of | |
3447 | type 's', which are automatically initialized to point to the new | |
3448 | structure itself; fields with protection 'o' can not be initialized by | |
3449 | Scheme programs. | |
3450 | ||
3451 | If fewer optional arguments than initializable fields are supplied, | |
3452 | fields of type 'p' get default value #f while fields of type 'u' are | |
3453 | initialized to 0. | |
3454 | ||
3455 | Structs are currently the basic representation for record-like data | |
3456 | structures in Guile. The plan is to eventually replace them with a | |
3457 | new representation which will at the same time be easier to use and | |
3458 | more powerful. | |
3459 | ||
3460 | For more information, see the documentation for @code{make-vtable-vtable}. | |
3461 | @end deffn | |
3462 | ||
3463 | @c docstring begin (texi-doc-string "guile" "struct?") | |
3464 | @deffn primitive struct? x | |
780ee65e NJ |
3465 | Return @code{#t} iff @var{obj} is a structure object, else |
3466 | @code{#f}. | |
38a93523 NJ |
3467 | @end deffn |
3468 | ||
3469 | ||
3470 | @c docstring begin (texi-doc-string "guile" "struct-ref") | |
3471 | @c docstring begin (texi-doc-string "guile" "struct-set!") | |
3472 | @deffn primitive struct-ref handle pos | |
3473 | @deffnx primitive struct-set! struct n value | |
3474 | Access (or modify) the @var{n}th field of @var{struct}. | |
3475 | ||
3476 | If the field is of type 'p', then it can be set to an arbitrary value. | |
3477 | ||
3478 | If the field is of type 'u', then it can only be set to a non-negative | |
3479 | integer value small enough to fit in one machine word. | |
3480 | @end deffn | |
3481 | ||
3482 | ||
3483 | ||
3484 | @node Vtables | |
3485 | @subsection Vtables | |
3486 | ||
3487 | Vtables are structures that are used to represent structure types. Each | |
3488 | vtable contains a layout specification in field | |
3489 | @code{vtable-index-layout} -- instances of the type are laid out | |
3490 | according to that specification. Vtables contain additional fields | |
3491 | which are used only internally to libguile. The variable | |
3492 | @code{vtable-offset-user} is bound to a field number. Vtable fields | |
3493 | at that position or greater are user definable. | |
3494 | ||
3495 | @c docstring begin (texi-doc-string "guile" "struct-vtable") | |
3496 | @deffn primitive struct-vtable handle | |
3497 | Return the vtable structure that describes the type of @var{struct}. | |
3498 | @end deffn | |
3499 | ||
3500 | @c docstring begin (texi-doc-string "guile" "struct-vtable?") | |
3501 | @deffn primitive struct-vtable? x | |
780ee65e | 3502 | Return @code{#t} iff obj is a vtable structure. |
38a93523 NJ |
3503 | @end deffn |
3504 | ||
3505 | If you have a vtable structure, @code{V}, you can create an instance of | |
3506 | the type it describes by using @code{(make-struct V ...)}. But where | |
3507 | does @code{V} itself come from? One possibility is that @code{V} is an | |
3508 | instance of a user-defined vtable type, @code{V'}, so that @code{V} is | |
3509 | created by using @code{(make-struct V' ...)}. Another possibility is | |
3510 | that @code{V} is an instance of the type it itself describes. Vtable | |
3511 | structures of the second sort are created by this procedure: | |
3512 | ||
3513 | @c docstring begin (texi-doc-string "guile" "make-vtable-vtable") | |
3514 | @deffn primitive make-vtable-vtable user_fields tail_array_size . init | |
3515 | Return a new, self-describing vtable structure. | |
3516 | ||
3517 | @var{user-fields} is a string describing user defined fields of the | |
3518 | vtable beginning at index @code{vtable-offset-user} | |
3519 | (see @code{make-struct-layout}). | |
3520 | ||
3521 | @var{tail-size} specifies the size of the tail-array (if any) of | |
3522 | this vtable. | |
3523 | ||
3524 | @var{init1}, @dots{} are the optional initializers for the fields of | |
3525 | the vtable. | |
3526 | ||
3527 | Vtables have one initializable system field---the struct printer. | |
3528 | This field comes before the user fields in the initializers passed | |
3529 | to @code{make-vtable-vtable} and @code{make-struct}, and thus works as | |
3530 | a third optional argument to @code{make-vtable-vtable} and a fourth to | |
3531 | @code{make-struct} when creating vtables: | |
3532 | ||
3533 | If the value is a procedure, it will be called instead of the standard | |
3534 | printer whenever a struct described by this vtable is printed. | |
3535 | The procedure will be called with arguments STRUCT and PORT. | |
3536 | ||
3537 | The structure of a struct is described by a vtable, so the vtable is | |
3538 | in essence the type of the struct. The vtable is itself a struct with | |
3539 | a vtable. This could go on forever if it weren't for the | |
3540 | vtable-vtables which are self-describing vtables, and thus terminate | |
3541 | the chain. | |
3542 | ||
3543 | There are several potential ways of using structs, but the standard | |
3544 | one is to use three kinds of structs, together building up a type | |
3545 | sub-system: one vtable-vtable working as the root and one or several | |
3546 | "types", each with a set of "instances". (The vtable-vtable should be | |
3547 | compared to the class <class> which is the class of itself.) | |
3548 | ||
3549 | @example | |
3550 | (define ball-root (make-vtable-vtable "pr" 0)) | |
3551 | ||
3552 | (define (make-ball-type ball-color) | |
3553 | (make-struct ball-root 0 | |
3554 | (make-struct-layout "pw") | |
3555 | (lambda (ball port) | |
3556 | (format port "#<a ~A ball owned by ~A>" | |
3557 | (color ball) | |
3558 | (owner ball))) | |
3559 | ball-color)) | |
3560 | (define (color ball) (struct-ref (struct-vtable ball) vtable-offset-user)) | |
3561 | (define (owner ball) (struct-ref ball 0)) | |
3562 | ||
3563 | (define red (make-ball-type 'red)) | |
3564 | (define green (make-ball-type 'green)) | |
3565 | ||
3566 | (define (make-ball type owner) (make-struct type 0 owner)) | |
3567 | ||
3568 | (define ball (make-ball green 'Nisse)) | |
3569 | ball @result{} #<a green ball owned by Nisse> | |
3570 | @end example | |
3571 | @end deffn | |
3572 | ||
3573 | @c docstring begin (texi-doc-string "guile" "struct-vtable-name") | |
3574 | @deffn primitive struct-vtable-name vtable | |
3575 | Return the name of the vtable @var{vtable}. | |
3576 | @end deffn | |
3577 | ||
3578 | @c docstring begin (texi-doc-string "guile" "set-struct-vtable-name!") | |
3579 | @deffn primitive set-struct-vtable-name! vtable name | |
3580 | Set the name of the vtable @var{vtable} to @var{name}. | |
3581 | @end deffn | |
3582 | ||
3583 | @c docstring begin (texi-doc-string "guile" "struct-vtable-tag") | |
3584 | @deffn primitive struct-vtable-tag handle | |
3585 | Return the vtable tag of the structure @var{handle}. | |
3586 | @end deffn | |
3587 | ||
3588 | ||
3589 | @node Arrays | |
3590 | @section Arrays | |
3591 | ||
3592 | @menu | |
3593 | * Conventional Arrays:: Arrays with arbitrary data. | |
3594 | * Array Mapping:: Applying a procedure to the contents of an array. | |
3595 | * Uniform Arrays:: Arrays with data of a single type. | |
3596 | * Bit Vectors:: Vectors of bits. | |
3597 | @end menu | |
3598 | ||
3599 | @node Conventional Arrays | |
3600 | @subsection Conventional Arrays | |
3601 | ||
3602 | @dfn{Conventional arrays} are a collection of cells organised into an | |
3603 | arbitrary number of dimensions. Each cell can hold any kind of Scheme | |
3604 | value and can be accessed in constant time by supplying an index for | |
3605 | each dimension. This contrasts with uniform arrays, which use memory | |
3606 | more efficiently but can hold data of only a single type, and lists | |
3607 | where inserting and deleting cells is more efficient, but more time | |
3608 | is usually required to access a particular cell. | |
3609 | ||
3610 | A conventional array is displayed as @code{#} followed by the @dfn{rank} | |
3611 | (number of dimensions) followed by the cells, organised into dimensions | |
3612 | using parentheses. The nesting depth of the parentheses is equal to | |
3613 | the rank. | |
3614 | ||
3615 | When an array is created, the number of dimensions and range of each | |
3616 | dimension must be specified, e.g., to create a 2x3 array with a | |
3617 | zero-based index: | |
3618 | ||
3619 | @example | |
3620 | (make-array 'ho 2 3) @result{} | |
3621 | #2((ho ho ho) (ho ho ho)) | |
3622 | @end example | |
3623 | ||
3624 | The range of each dimension can also be given explicitly, e.g., another | |
3625 | way to create the same array: | |
3626 | ||
3627 | @example | |
3628 | (make-array 'ho '(0 1) '(0 2)) @result{} | |
3629 | #2((ho ho ho) (ho ho ho)) | |
3630 | @end example | |
3631 | ||
3632 | A conventional array with one dimension based at zero is identical to | |
3633 | a vector: | |
3634 | ||
3635 | @example | |
3636 | (make-array 'ho 3) @result{} | |
3637 | #(ho ho ho) | |
3638 | @end example | |
3639 | ||
3640 | The following procedures can be used with conventional arrays (or vectors). | |
3641 | ||
3642 | @c docstring begin (texi-doc-string "guile" "array?") | |
3643 | @deffn primitive array? v [prot] | |
3644 | Returns @code{#t} if the @var{obj} is an array, and @code{#f} if not. | |
3645 | ||
3646 | The @var{prototype} argument is used with uniform arrays and is described | |
3647 | elsewhere. | |
3648 | @end deffn | |
3649 | ||
3650 | @deffn procedure make-array initial-value bound1 bound2 @dots{} | |
3651 | Creates and returns an array that has as many dimensions as there are | |
3652 | @var{bound}s and fills it with @var{initial-value}. | |
3653 | @end deffn | |
3654 | ||
3655 | @c array-ref's type is `compiled-closure'. There's some weird stuff | |
3656 | @c going on in array.c, too. Let's call it a primitive. -twp | |
3657 | ||
3658 | @c docstring begin (texi-doc-string "guile" "uniform-vector-ref") | |
3659 | @c docstring begin (texi-doc-string "guile" "array-ref") | |
3660 | @deffn primitive uniform-vector-ref v args | |
3661 | @deffnx primitive array-ref v . args | |
3662 | Returns the element at the @code{(index1, index2)} element in @var{array}. | |
3663 | @end deffn | |
3664 | ||
3665 | @c docstring begin (texi-doc-string "guile" "array-in-bounds?") | |
3666 | @deffn primitive array-in-bounds? v . args | |
3667 | Returns @code{#t} if its arguments would be acceptable to array-ref. | |
3668 | @end deffn | |
3669 | ||
3670 | @c docstring begin (texi-doc-string "guile" "array-set!") | |
3671 | @c docstring begin (texi-doc-string "guile" "uniform-array-set1!") | |
3672 | @deffn primitive array-set! v obj . args | |
3673 | @deffnx primitive uniform-array-set1! v obj args | |
3674 | Sets the element at the @code{(index1, index2)} element in @var{array} to | |
3675 | @var{new-value}. The value returned by array-set! is unspecified. | |
3676 | @end deffn | |
3677 | ||
3678 | @c docstring begin (texi-doc-string "guile" "make-shared-array") | |
3679 | @deffn primitive make-shared-array oldra mapfunc . dims | |
3680 | @code{make-shared-array} can be used to create shared subarrays of other | |
3681 | arrays. The @var{mapper} is a function that translates coordinates in | |
3682 | the new array into coordinates in the old array. A @var{mapper} must be | |
3683 | linear, and its range must stay within the bounds of the old array, but | |
3684 | it can be otherwise arbitrary. A simple example: | |
3685 | @example | |
3686 | (define fred (make-array #f 8 8)) | |
3687 | (define freds-diagonal | |
3688 | (make-shared-array fred (lambda (i) (list i i)) 8)) | |
3689 | (array-set! freds-diagonal 'foo 3) | |
3690 | (array-ref fred 3 3) @result{} foo | |
3691 | (define freds-center | |
3692 | (make-shared-array fred (lambda (i j) (list (+ 3 i) (+ 3 j))) 2 2)) | |
3693 | (array-ref freds-center 0 0) @result{} foo | |
3694 | @end example | |
3695 | @end deffn | |
3696 | ||
3697 | @c docstring begin (texi-doc-string "guile" "shared-array-increments") | |
3698 | @deffn primitive shared-array-increments ra | |
3699 | For each dimension, return the distance between elements in the root vector. | |
3700 | @end deffn | |
3701 | ||
3702 | @c docstring begin (texi-doc-string "guile" "shared-array-offset") | |
3703 | @deffn primitive shared-array-offset ra | |
3704 | Return the root vector index of the first element in the array. | |
3705 | @end deffn | |
3706 | ||
3707 | @c docstring begin (texi-doc-string "guile" "shared-array-root") | |
3708 | @deffn primitive shared-array-root ra | |
3709 | Return the root vector of a shared array. | |
3710 | @end deffn | |
3711 | ||
3712 | @c docstring begin (texi-doc-string "guile" "transpose-array") | |
3713 | @deffn primitive transpose-array ra . args | |
3714 | Returns an array sharing contents with @var{array}, but with dimensions | |
3715 | arranged in a different order. There must be one @var{dim} argument for | |
3716 | each dimension of @var{array}. @var{dim0}, @var{dim1}, @dots{} should | |
3717 | be integers between 0 and the rank of the array to be returned. Each | |
3718 | integer in that range must appear at least once in the argument list. | |
3719 | ||
3720 | The values of @var{dim0}, @var{dim1}, @dots{} correspond to dimensions | |
3721 | in the array to be returned, their positions in the argument list to | |
3722 | dimensions of @var{array}. Several @var{dim}s may have the same value, | |
3723 | in which case the returned array will have smaller rank than | |
3724 | @var{array}. | |
3725 | ||
3726 | examples: | |
3727 | @example | |
3728 | (transpose-array '#2((a b) (c d)) 1 0) @result{} #2((a c) (b d)) | |
3729 | (transpose-array '#2((a b) (c d)) 0 0) @result{} #1(a d) | |
3730 | (transpose-array '#3(((a b c) (d e f)) ((1 2 3) (4 5 6))) 1 1 0) @result{} | |
3731 | #2((a 4) (b 5) (c 6)) | |
3732 | @end example | |
3733 | @end deffn | |
3734 | ||
3735 | @c docstring begin (texi-doc-string "guile" "enclose-array") | |
3736 | @deffn primitive enclose-array ra . axes | |
3737 | @var{dim0}, @var{dim1} @dots{} should be nonnegative integers less than | |
3738 | the rank of @var{array}. @var{enclose-array} returns an array | |
3739 | resembling an array of shared arrays. The dimensions of each shared | |
3740 | array are the same as the @var{dim}th dimensions of the original array, | |
3741 | the dimensions of the outer array are the same as those of the original | |
3742 | array that did not match a @var{dim}. | |
3743 | ||
3744 | An enclosed array is not a general Scheme array. Its elements may not | |
3745 | be set using @code{array-set!}. Two references to the same element of | |
3746 | an enclosed array will be @code{equal?} but will not in general be | |
3747 | @code{eq?}. The value returned by @var{array-prototype} when given an | |
3748 | enclosed array is unspecified. | |
3749 | ||
3750 | examples: | |
3751 | @example | |
3752 | (enclose-array '#3(((a b c) (d e f)) ((1 2 3) (4 5 6))) 1) @result{} | |
3753 | #<enclosed-array (#1(a d) #1(b e) #1(c f)) (#1(1 4) #1(2 5) #1(3 6))> | |
3754 | ||
3755 | (enclose-array '#3(((a b c) (d e f)) ((1 2 3) (4 5 6))) 1 0) @result{} | |
3756 | #<enclosed-array #2((a 1) (d 4)) #2((b 2) (e 5)) #2((c 3) (f 6))> | |
3757 | @end example | |
3758 | @end deffn | |
3759 | ||
3760 | @deffn procedure array-shape array | |
3761 | Returns a list of inclusive bounds of integers. | |
3762 | @example | |
3763 | (array-shape (make-array 'foo '(-1 3) 5)) @result{} ((-1 3) (0 4)) | |
3764 | @end example | |
3765 | @end deffn | |
3766 | ||
3767 | @c docstring begin (texi-doc-string "guile" "array-dimensions") | |
3768 | @deffn primitive array-dimensions ra | |
3769 | @code{Array-dimensions} is similar to @code{array-shape} but replaces | |
3770 | elements with a @code{0} minimum with one greater than the maximum. So: | |
3771 | @example | |
3772 | (array-dimensions (make-array 'foo '(-1 3) 5)) @result{} ((-1 3) 5) | |
3773 | @end example | |
3774 | @end deffn | |
3775 | ||
3776 | @c docstring begin (texi-doc-string "guile" "array-rank") | |
3777 | @deffn primitive array-rank ra | |
3778 | Returns the number of dimensions of @var{obj}. If @var{obj} is not an | |
3779 | array, @code{0} is returned. | |
3780 | @end deffn | |
3781 | ||
3782 | @c docstring begin (texi-doc-string "guile" "array->list") | |
3783 | @deffn primitive array->list v | |
3784 | Returns a list consisting of all the elements, in order, of @var{array}. | |
3785 | @end deffn | |
3786 | ||
3787 | @c docstring begin (texi-doc-string "guile" "array-copy!") | |
3788 | @c docstring begin (texi-doc-string "guile" "array-copy-in-order!") | |
3789 | @deffn primitive array-copy! src dst | |
3790 | @deffnx primitive array-copy-in-order! src dst | |
3791 | Copies every element from vector or array @var{source} to the | |
3792 | corresponding element of @var{destination}. @var{destination} must have | |
3793 | the same rank as @var{source}, and be at least as large in each | |
3794 | dimension. The order is unspecified. | |
3795 | @end deffn | |
3796 | ||
3797 | @c docstring begin (texi-doc-string "guile" "array-fill!") | |
3798 | @deffn primitive array-fill! ra fill | |
3799 | Stores @var{fill} in every element of @var{array}. The value returned | |
3800 | is unspecified. | |
3801 | @end deffn | |
3802 | ||
3803 | @c begin (texi-doc-string "guile" "array-equal?") | |
3804 | @deffn primitive array-equal? ra0 ra1 | |
3805 | Returns @code{#t} iff all arguments are arrays with the same shape, the | |
3806 | same type, and have corresponding elements which are either | |
3807 | @code{equal?} or @code{array-equal?}. This function differs from | |
3808 | @code{equal?} in that a one dimensional shared array may be | |
3809 | @var{array-equal?} but not @var{equal?} to a vector or uniform vector. | |
3810 | @end deffn | |
3811 | ||
3812 | @c docstring begin (texi-doc-string "guile" "array-contents") | |
3813 | @deffn primitive array-contents ra [strict] | |
3814 | @deffnx primitive array-contents array strict | |
3815 | If @var{array} may be @dfn{unrolled} into a one dimensional shared array | |
3816 | without changing their order (last subscript changing fastest), then | |
3817 | @code{array-contents} returns that shared array, otherwise it returns | |
3818 | @code{#f}. All arrays made by @var{make-array} and | |
3819 | @var{make-uniform-array} may be unrolled, some arrays made by | |
3820 | @var{make-shared-array} may not be. | |
3821 | ||
3822 | If the optional argument @var{strict} is provided, a shared array will | |
3823 | be returned only if its elements are stored internally contiguous in | |
3824 | memory. | |
3825 | @end deffn | |
3826 | ||
3827 | @node Array Mapping | |
3828 | @subsection Array Mapping | |
3829 | ||
3830 | @c docstring begin (texi-doc-string "guile" "array-map!") | |
3831 | @c docstring begin (texi-doc-string "guile" "array-map-in-order!") | |
3832 | @deffn primitive array-map! ra0 proc . lra | |
3833 | @deffnx primitive array-map-in-order! ra0 proc . lra | |
3834 | @var{array1}, @dots{} must have the same number of dimensions as | |
3835 | @var{array0} and have a range for each index which includes the range | |
3836 | for the corresponding index in @var{array0}. @var{proc} is applied to | |
3837 | each tuple of elements of @var{array1} @dots{} and the result is stored | |
3838 | as the corresponding element in @var{array0}. The value returned is | |
3839 | unspecified. The order of application is unspecified. | |
3840 | @end deffn | |
3841 | ||
3842 | @c docstring begin (texi-doc-string "guile" "array-for-each") | |
3843 | @deffn primitive array-for-each proc ra0 . lra | |
3844 | @var{proc} is applied to each tuple of elements of @var{array0} @dots{} | |
3845 | in row-major order. The value returned is unspecified. | |
3846 | @end deffn | |
3847 | ||
3848 | @c docstring begin (texi-doc-string "guile" "array-index-map!") | |
3849 | @deffn primitive array-index-map! ra proc | |
3850 | applies @var{proc} to the indices of each element of @var{array} in | |
3851 | turn, storing the result in the corresponding element. The value | |
3852 | returned and the order of application are unspecified. | |
3853 | ||
3854 | One can implement @var{array-indexes} as | |
3855 | @example | |
3856 | (define (array-indexes array) | |
3857 | (let ((ra (apply make-array #f (array-shape array)))) | |
3858 | (array-index-map! ra (lambda x x)) | |
3859 | ra)) | |
3860 | @end example | |
3861 | Another example: | |
3862 | @example | |
3863 | (define (apl:index-generator n) | |
3864 | (let ((v (make-uniform-vector n 1))) | |
3865 | (array-index-map! v (lambda (i) i)) | |
3866 | v)) | |
3867 | @end example | |
3868 | @end deffn | |
3869 | ||
3870 | @node Uniform Arrays | |
3871 | @subsection Uniform Arrays | |
3872 | ||
3873 | @noindent | |
3874 | @dfn{Uniform arrays} have elements all of the | |
3875 | same type and occupy less storage than conventional | |
3876 | arrays. Uniform arrays with a single zero-based dimension | |
3877 | are also known as @dfn{uniform vectors}. The procedures in | |
3878 | this section can also be used on conventional arrays, vectors, | |
3879 | bit-vectors and strings. | |
3880 | ||
3881 | @noindent | |
3882 | When creating a uniform array, the type of data to be stored | |
3883 | is indicated with a @var{prototype} argument. The following table | |
3884 | lists the types available and example prototypes: | |
3885 | ||
3886 | @example | |
3887 | prototype type printing character | |
3888 | ||
3889 | #t boolean (bit-vector) b | |
3890 | #\a char (string) a | |
3891 | #\nul byte (integer) y | |
3892 | 's short (integer) h | |
3893 | 1 unsigned long (integer) u | |
3894 | -1 signed long (integer) e | |
3895 | 'l signed long long (integer) l | |
3896 | 1.0 float (single precision) s | |
3897 | 1/3 double (double precision float) i | |
3898 | 0+i complex (double precision) c | |
3899 | () conventional vector | |
3900 | @end example | |
3901 | ||
3902 | @noindent | |
3903 | Unshared uniform arrays of characters with a single zero-based dimension | |
3904 | are identical to strings: | |
3905 | ||
3906 | @example | |
3907 | (make-uniform-array #\a 3) @result{} | |
3908 | "aaa" | |
3909 | @end example | |
3910 | ||
3911 | @noindent | |
3912 | Unshared uniform arrays of booleans with a single zero-based dimension | |
3913 | are identical to @ref{Bit Vectors, bit-vectors}. | |
3914 | ||
3915 | @example | |
3916 | (make-uniform-array #t 3) @result{} | |
3917 | #*111 | |
3918 | @end example | |
3919 | ||
3920 | @noindent | |
3921 | Other uniform vectors are written in a form similar to that of vectors, | |
3922 | except that a single character from the above table is put between | |
3923 | @code{#} and @code{(}. For example, a uniform vector of signed | |
3924 | long integers is displayed in the form @code{'#e(3 5 9)}. | |
3925 | ||
3926 | @c docstring begin (texi-doc-string "guile" "array?") | |
3927 | @deffn primitive array? v [prot] | |
3928 | Returns @code{#t} if the @var{obj} is an array, and @code{#f} if not. | |
3929 | ||
3930 | The @var{prototype} argument is used with uniform arrays and is described | |
3931 | elsewhere. | |
3932 | @end deffn | |
3933 | ||
3934 | @deffn procedure make-uniform-array prototype bound1 bound2 @dots{} | |
3935 | Creates and returns a uniform array of type corresponding to | |
3936 | @var{prototype} that has as many dimensions as there are @var{bound}s | |
3937 | and fills it with @var{prototype}. | |
3938 | @end deffn | |
3939 | ||
3940 | @c docstring begin (texi-doc-string "guile" "array-prototype") | |
3941 | @deffn primitive array-prototype ra | |
3942 | Returns an object that would produce an array of the same type as | |
3943 | @var{array}, if used as the @var{prototype} for | |
3944 | @code{make-uniform-array}. | |
3945 | @end deffn | |
3946 | ||
3947 | @c docstring begin (texi-doc-string "guile" "list->uniform-array") | |
3948 | @deffn primitive list->uniform-array ndim prot lst | |
3949 | @deffnx procedure list->uniform-vector prot lst | |
3950 | Returns a uniform array of the type indicated by prototype @var{prot} | |
3951 | with elements the same as those of @var{lst}. Elements must be of the | |
3952 | appropriate type, no coercions are done. | |
3953 | @end deffn | |
3954 | ||
3955 | @deffn primitive uniform-vector-fill! uve fill | |
3956 | Stores @var{fill} in every element of @var{uve}. The value returned is | |
3957 | unspecified. | |
3958 | @end deffn | |
3959 | ||
3960 | @c docstring begin (texi-doc-string "guile" "uniform-vector-length") | |
3961 | @deffn primitive uniform-vector-length v | |
3962 | Returns the number of elements in @var{uve}. | |
3963 | @end deffn | |
3964 | ||
3965 | @c docstring begin (texi-doc-string "guile" "dimensions->uniform-array") | |
3966 | @deffn primitive dimensions->uniform-array dims prot [fill] | |
3967 | @deffnx primitive make-uniform-vector length prototype [fill] | |
3968 | Creates and returns a uniform array or vector of type corresponding to | |
3969 | @var{prototype} with dimensions @var{dims} or length @var{length}. If | |
3970 | @var{fill} is supplied, it's used to fill the array, otherwise | |
3971 | @var{prototype} is used. | |
3972 | @end deffn | |
3973 | ||
3974 | @c Another compiled-closure. -twp | |
3975 | ||
3976 | @c docstring begin (texi-doc-string "guile" "uniform-array-read!") | |
3977 | @deffn primitive uniform-array-read! ra [port_or_fd [start [end]]] | |
3978 | @deffnx primitive uniform-vector-read! uve [port-or-fdes] [start] [end] | |
3979 | Attempts to read all elements of @var{ura}, in lexicographic order, as | |
3980 | binary objects from @var{port-or-fdes}. | |
3981 | If an end of file is encountered during | |
3982 | uniform-array-read! the objects up to that point only are put into @var{ura} | |
3983 | (starting at the beginning) and the remainder of the array is | |
3984 | unchanged. | |
3985 | ||
3986 | The optional arguments @var{start} and @var{end} allow | |
3987 | a specified region of a vector (or linearized array) to be read, | |
3988 | leaving the remainder of the vector unchanged. | |
3989 | ||
3990 | @code{uniform-array-read!} returns the number of objects read. | |
3991 | @var{port-or-fdes} may be omitted, in which case it defaults to the value | |
3992 | returned by @code{(current-input-port)}. | |
3993 | @end deffn | |
3994 | ||
3995 | @c docstring begin (texi-doc-string "guile" "uniform-array-write") | |
3996 | @deffn primitive uniform-array-write v [port_or_fd [start [end]]] | |
3997 | @deffnx primitive uniform-vector-write uve [port-or-fdes] [start] [end] | |
3998 | Writes all elements of @var{ura} as binary objects to | |
3999 | @var{port-or-fdes}. | |
4000 | ||
4001 | The optional arguments @var{start} | |
4002 | and @var{end} allow | |
4003 | a specified region of a vector (or linearized array) to be written. | |
4004 | ||
4005 | The number of objects actually written is returned. | |
4006 | @var{port-or-fdes} may be | |
4007 | omitted, in which case it defaults to the value returned by | |
4008 | @code{(current-output-port)}. | |
4009 | @end deffn | |
4010 | ||
4011 | @node Bit Vectors | |
4012 | @subsection Bit Vectors | |
4013 | ||
4014 | @noindent | |
4015 | Bit vectors are a specific type of uniform array: an array of booleans | |
4016 | with a single zero-based index. | |
4017 | ||
4018 | @noindent | |
4019 | They are displayed as a sequence of @code{0}s and | |
4020 | @code{1}s prefixed by @code{#*}, e.g., | |
4021 | ||
4022 | @example | |
4023 | (make-uniform-vector 8 #t #f) @result{} | |
4024 | #*00000000 | |
4025 | ||
4026 | #b(#t #f #t) @result{} | |
4027 | #*101 | |
4028 | @end example | |
4029 | ||
4030 | @c docstring begin (texi-doc-string "guile" "bit-count") | |
4031 | @deffn primitive bit-count b bitvector | |
4032 | Returns the number of occurrences of the boolean @var{b} in | |
4033 | @var{bitvector}. | |
4034 | @end deffn | |
4035 | ||
4036 | @c docstring begin (texi-doc-string "guile" "bit-position") | |
4037 | @deffn primitive bit-position item v k | |
4038 | Returns the minimum index of an occurrence of @var{bool} in @var{bv} | |
4039 | which is at least @var{k}. If no @var{bool} occurs within the specified | |
4040 | range @code{#f} is returned. | |
4041 | @end deffn | |
4042 | ||
4043 | @c docstring begin (texi-doc-string "guile" "bit-invert!") | |
4044 | @deffn primitive bit-invert! v | |
4045 | Modifies @var{bv} by replacing each element with its negation. | |
4046 | @end deffn | |
4047 | ||
4048 | @c docstring begin (texi-doc-string "guile" "bit-set*!") | |
4049 | @deffn primitive bit-set*! v kv obj | |
4050 | If uve is a bit-vector @var{bv} and uve must be of the same | |
4051 | length. If @var{bool} is @code{#t}, uve is OR'ed into | |
4052 | @var{bv}; If @var{bool} is @code{#f}, the inversion of uve is | |
4053 | AND'ed into @var{bv}. | |
4054 | ||
4055 | If uve is a unsigned integer vector all the elements of uve | |
4056 | must be between 0 and the @code{length} of @var{bv}. The bits | |
4057 | of @var{bv} corresponding to the indexes in uve are set to | |
4058 | @var{bool}. The return value is unspecified. | |
4059 | @end deffn | |
4060 | ||
4061 | @c docstring begin (texi-doc-string "guile" "bit-count*") | |
4062 | @deffn primitive bit-count* v kv obj | |
4063 | Returns | |
4064 | @example | |
4065 | (bit-count (bit-set*! (if bool bv (bit-invert! bv)) uve #t) #t). | |
4066 | @end example | |
4067 | @var{bv} is not modified. | |
4068 | @end deffn | |
4069 | ||
4070 | ||
4071 | @node Association Lists and Hash Tables | |
4072 | @section Association Lists and Hash Tables | |
4073 | ||
4074 | This chapter discusses dictionary objects: data structures that are | |
4075 | useful for organizing and indexing large bodies of information. | |
4076 | ||
4077 | @menu | |
4078 | * Dictionary Types:: About dictionary types; what they're good for. | |
4079 | * Association Lists:: | |
4080 | * Hash Tables:: | |
4081 | @end menu | |
4082 | ||
4083 | @node Dictionary Types | |
4084 | @subsection Dictionary Types | |
4085 | ||
4086 | A @dfn{dictionary} object is a data structure used to index | |
4087 | information in a user-defined way. In standard Scheme, the main | |
4088 | aggregate data types are lists and vectors. Lists are not really | |
4089 | indexed at all, and vectors are indexed only by number | |
4090 | (e.g. @code{(vector-ref foo 5)}). Often you will find it useful | |
4091 | to index your data on some other type; for example, in a library | |
4092 | catalog you might want to look up a book by the name of its | |
4093 | author. Dictionaries are used to help you organize information in | |
4094 | such a way. | |
4095 | ||
4096 | An @dfn{association list} (or @dfn{alist} for short) is a list of | |
4097 | key-value pairs. Each pair represents a single quantity or | |
4098 | object; the @code{car} of the pair is a key which is used to | |
4099 | identify the object, and the @code{cdr} is the object's value. | |
4100 | ||
4101 | A @dfn{hash table} also permits you to index objects with | |
4102 | arbitrary keys, but in a way that makes looking up any one object | |
4103 | extremely fast. A well-designed hash system makes hash table | |
4104 | lookups almost as fast as conventional array or vector references. | |
4105 | ||
4106 | Alists are popular among Lisp programmers because they use only | |
4107 | the language's primitive operations (lists, @dfn{car}, @dfn{cdr} | |
4108 | and the equality primitives). No changes to the language core are | |
4109 | necessary. Therefore, with Scheme's built-in list manipulation | |
4110 | facilities, it is very convenient to handle data stored in an | |
4111 | association list. Also, alists are highly portable and can be | |
4112 | easily implemented on even the most minimal Lisp systems. | |
4113 | ||
4114 | However, alists are inefficient, especially for storing large | |
4115 | quantities of data. Because we want Guile to be useful for large | |
4116 | software systems as well as small ones, Guile provides a rich set | |
4117 | of tools for using either association lists or hash tables. | |
4118 | ||
4119 | @node Association Lists | |
4120 | @subsection Association Lists | |
4121 | @cindex Association List | |
4122 | @cindex Alist | |
4123 | @cindex Database | |
4124 | ||
4125 | An association list is a conventional data structure that is often used | |
4126 | to implement simple key-value databases. It consists of a list of | |
4127 | entries in which each entry is a pair. The @dfn{key} of each entry is | |
4128 | the @code{car} of the pair and the @dfn{value} of each entry is the | |
4129 | @code{cdr}. | |
4130 | ||
4131 | @example | |
4132 | ASSOCIATION LIST ::= '( (KEY1 . VALUE1) | |
4133 | (KEY2 . VALUE2) | |
4134 | (KEY3 . VALUE3) | |
4135 | @dots{} | |
4136 | ) | |
4137 | @end example | |
4138 | ||
4139 | @noindent | |
4140 | Association lists are also known, for short, as @dfn{alists}. | |
4141 | ||
4142 | The structure of an association list is just one example of the infinite | |
4143 | number of possible structures that can be built using pairs and lists. | |
4144 | As such, the keys and values in an association list can be manipulated | |
4145 | using the general list structure procedures @code{cons}, @code{car}, | |
4146 | @code{cdr}, @code{set-car!}, @code{set-cdr!} and so on. However, | |
4147 | because association lists are so useful, Guile also provides specific | |
4148 | procedures for manipulating them. | |
4149 | ||
4150 | @menu | |
4151 | * Alist Key Equality:: | |
4152 | * Adding or Setting Alist Entries:: | |
4153 | * Retrieving Alist Entries:: | |
4154 | * Removing Alist Entries:: | |
4155 | * Sloppy Alist Functions:: | |
4156 | * Alist Example:: | |
4157 | @end menu | |
4158 | ||
4159 | @node Alist Key Equality | |
4160 | @subsubsection Alist Key Equality | |
4161 | ||
4162 | All of Guile's dedicated association list procedures, apart from | |
4163 | @code{acons}, come in three flavours, depending on the level of equality | |
4164 | that is required to decide whether an existing key in the association | |
4165 | list is the same as the key that the procedure call uses to identify the | |
4166 | required entry. | |
4167 | ||
4168 | @itemize @bullet | |
4169 | @item | |
4170 | Procedures with @dfn{assq} in their name use @code{eq?} to determine key | |
4171 | equality. | |
4172 | ||
4173 | @item | |
4174 | Procedures with @dfn{assv} in their name use @code{eqv?} to determine | |
4175 | key equality. | |
4176 | ||
4177 | @item | |
4178 | Procedures with @dfn{assoc} in their name use @code{equal?} to | |
4179 | determine key equality. | |
4180 | @end itemize | |
4181 | ||
4182 | @code{acons} is an exception because it is used to build association | |
4183 | lists which do not require their entries' keys to be unique. | |
4184 | ||
4185 | @node Adding or Setting Alist Entries | |
4186 | @subsubsection Adding or Setting Alist Entries | |
38a93523 NJ |
4187 | |
4188 | @code{acons} adds a new entry to an association list and returns the | |
4189 | combined association list. The combined alist is formed by consing the | |
4190 | new entry onto the head of the alist specified in the @code{acons} | |
4191 | procedure call. So the specified alist is not modified, but its | |
4192 | contents become shared with the tail of the combined alist that | |
4193 | @code{acons} returns. | |
4194 | ||
4195 | In the most common usage of @code{acons}, a variable holding the | |
4196 | original association list is updated with the combined alist: | |
4197 | ||
4198 | @example | |
4199 | (set! address-list (acons name address address-list)) | |
4200 | @end example | |
4201 | ||
4202 | In such cases, it doesn't matter that the old and new values of | |
4203 | @code{address-list} share some of their contents, since the old value is | |
4204 | usually no longer independently accessible. | |
4205 | ||
4206 | Note that @code{acons} adds the specified new entry regardless of | |
4207 | whether the alist may already contain entries with keys that are, in | |
4208 | some sense, the same as that of the new entry. Thus @code{acons} is | |
4209 | ideal for building alists where there is no concept of key uniqueness. | |
4210 | ||
4211 | @example | |
4212 | (set! task-list (acons 3 "pay gas bill" '())) | |
4213 | task-list | |
4214 | @result{} | |
4215 | ((3 . "pay gas bill")) | |
4216 | ||
4217 | (set! task-list (acons 3 "tidy bedroom" task-list)) | |
4218 | task-list | |
4219 | @result{} | |
4220 | ((3 . "tidy bedroom") (3 . "pay gas bill")) | |
4221 | @end example | |
4222 | ||
4223 | @code{assq-set!}, @code{assv-set!} and @code{assoc-set!} are used to add | |
4224 | or replace an entry in an association list where there @emph{is} a | |
4225 | concept of key uniqueness. If the specified association list already | |
4226 | contains an entry whose key is the same as that specified in the | |
4227 | procedure call, the existing entry is replaced by the new one. | |
4228 | Otherwise, the new entry is consed onto the head of the old association | |
4229 | list to create the combined alist. In all cases, these procedures | |
4230 | return the combined alist. | |
4231 | ||
4232 | @code{assq-set!} and friends @emph{may} destructively modify the | |
4233 | structure of the old association list in such a way that an existing | |
4234 | variable is correctly updated without having to @code{set!} it to the | |
4235 | value returned: | |
4236 | ||
4237 | @example | |
4238 | address-list | |
4239 | @result{} | |
4240 | (("mary" . "34 Elm Road") ("james" . "16 Bow Street")) | |
4241 | ||
4242 | (assoc-set! address-list "james" "1a London Road") | |
4243 | @result{} | |
4244 | (("mary" . "34 Elm Road") ("james" . "1a London Road")) | |
4245 | ||
4246 | address-list | |
4247 | @result{} | |
4248 | (("mary" . "34 Elm Road") ("james" . "1a London Road")) | |
4249 | @end example | |
4250 | ||
4251 | Or they may not: | |
4252 | ||
4253 | @example | |
4254 | (assoc-set! address-list "bob" "11 Newington Avenue") | |
4255 | @result{} | |
4256 | (("bob" . "11 Newington Avenue") ("mary" . "34 Elm Road") | |
4257 | ("james" . "1a London Road")) | |
4258 | ||
4259 | address-list | |
4260 | @result{} | |
4261 | (("mary" . "34 Elm Road") ("james" . "1a London Road")) | |
4262 | @end example | |
4263 | ||
4264 | The only safe way to update an association list variable when adding or | |
4265 | replacing an entry like this is to @code{set!} the variable to the | |
4266 | returned value: | |
4267 | ||
4268 | @example | |
4269 | (set! address-list | |
4270 | (assoc-set! address-list "bob" "11 Newington Avenue")) | |
4271 | address-list | |
4272 | @result{} | |
4273 | (("bob" . "11 Newington Avenue") ("mary" . "34 Elm Road") | |
4274 | ("james" . "1a London Road")) | |
4275 | @end example | |
4276 | ||
4277 | Because of this slight inconvenience, you may find it more convenient to | |
4278 | use hash tables to store dictionary data. If your application will not | |
4279 | be modifying the contents of an alist very often, this may not make much | |
4280 | difference to you. | |
4281 | ||
4282 | If you need to keep the old value of an association list in a form | |
4283 | independent from the list that results from modification by | |
4284 | @code{acons}, @code{assq-set!}, @code{assv-set!} or @code{assoc-set!}, | |
4285 | use @code{list-copy} to copy the old association list before modifying | |
4286 | it. | |
4287 | ||
4288 | @c docstring begin (texi-doc-string "guile" "acons") | |
4289 | @deffn primitive acons key value alist | |
4290 | Adds a new key-value pair to @var{alist}. A new pair is | |
4291 | created whose car is @var{key} and whose cdr is @var{value}, and the | |
4292 | pair is consed onto @var{alist}, and the new list is returned. This | |
4293 | function is @emph{not} destructive; @var{alist} is not modified. | |
4294 | @end deffn | |
4295 | ||
4296 | @c docstring begin (texi-doc-string "guile" "assq-set!") | |
4297 | @c docstring begin (texi-doc-string "guile" "assv-set!") | |
4298 | @c docstring begin (texi-doc-string "guile" "assoc-set!") | |
4299 | @deffn primitive assq-set! alist key val | |
4300 | @deffnx primitive assv-set! alist key value | |
4301 | @deffnx primitive assoc-set! alist key value | |
4302 | Reassociate @var{key} in @var{alist} with @var{value}: find any existing | |
4303 | @var{alist} entry for @var{key} and associate it with the new | |
4304 | @var{value}. If @var{alist} does not contain an entry for @var{key}, | |
4305 | add a new one. Return the (possibly new) alist. | |
4306 | ||
4307 | These functions do not attempt to verify the structure of @var{alist}, | |
4308 | and so may cause unusual results if passed an object that is not an | |
4309 | association list. | |
4310 | @end deffn | |
4311 | ||
4312 | @node Retrieving Alist Entries | |
4313 | @subsubsection Retrieving Alist Entries | |
38a93523 NJ |
4314 | @r5index assq |
4315 | @r5index assv | |
4316 | @r5index assoc | |
38a93523 NJ |
4317 | |
4318 | @code{assq}, @code{assv} and @code{assoc} take an alist and a key as | |
4319 | arguments and return the entry for that key if an entry exists, or | |
4320 | @code{#f} if there is no entry for that key. Note that, in the cases | |
4321 | where an entry exists, these procedures return the complete entry, that | |
4322 | is @code{(KEY . VALUE)}, not just the value. | |
4323 | ||
4324 | @c docstring begin (texi-doc-string "guile" "assq") | |
4325 | @c docstring begin (texi-doc-string "guile" "assv") | |
4326 | @c docstring begin (texi-doc-string "guile" "assoc") | |
4327 | @deffn primitive assq key alist | |
4328 | @deffnx primitive assv key alist | |
4329 | @deffnx primitive assoc key alist | |
4330 | Fetches the entry in @var{alist} that is associated with @var{key}. To | |
4331 | decide whether the argument @var{key} matches a particular entry in | |
4332 | @var{alist}, @code{assq} compares keys with @code{eq?}, @code{assv} | |
4333 | uses @code{eqv?} and @code{assoc} uses @code{equal?}. If @var{key} | |
4334 | cannot be found in @var{alist} (according to whichever equality | |
4335 | predicate is in use), then @code{#f} is returned. These functions | |
4336 | return the entire alist entry found (i.e. both the key and the value). | |
4337 | @end deffn | |
4338 | ||
4339 | @code{assq-ref}, @code{assv-ref} and @code{assoc-ref}, on the other | |
4340 | hand, take an alist and a key and return @emph{just the value} for that | |
4341 | key, if an entry exists. If there is no entry for the specified key, | |
4342 | these procedures return @code{#f}. | |
4343 | ||
4344 | This creates an ambiguity: if the return value is @code{#f}, it means | |
4345 | either that there is no entry with the specified key, or that there | |
4346 | @emph{is} an entry for the specified key, with value @code{#f}. | |
4347 | Consequently, @code{assq-ref} and friends should only be used where it | |
4348 | is known that an entry exists, or where the ambiguity doesn't matter | |
4349 | for some other reason. | |
4350 | ||
4351 | @c docstring begin (texi-doc-string "guile" "assq-ref") | |
4352 | @c docstring begin (texi-doc-string "guile" "assv-ref") | |
4353 | @c docstring begin (texi-doc-string "guile" "assoc-ref") | |
4354 | @deffn primitive assq-ref alist key | |
4355 | @deffnx primitive assv-ref alist key | |
4356 | @deffnx primitive assoc-ref alist key | |
4357 | Like @code{assq}, @code{assv} and @code{assoc}, except that only the | |
4358 | value associated with @var{key} in @var{alist} is returned. These | |
4359 | functions are equivalent to | |
4360 | ||
4361 | @lisp | |
4362 | (let ((ent (@var{associator} @var{key} @var{alist}))) | |
4363 | (and ent (cdr ent))) | |
4364 | @end lisp | |
4365 | ||
4366 | where @var{associator} is one of @code{assq}, @code{assv} or @code{assoc}. | |
4367 | @end deffn | |
4368 | ||
4369 | @node Removing Alist Entries | |
4370 | @subsubsection Removing Alist Entries | |
38a93523 NJ |
4371 | |
4372 | To remove the element from an association list whose key matches a | |
4373 | specified key, use @code{assq-remove!}, @code{assv-remove!} or | |
4374 | @code{assoc-remove!} (depending, as usual, on the level of equality | |
4375 | required between the key that you specify and the keys in the | |
4376 | association list). | |
4377 | ||
4378 | As with @code{assq-set!} and friends, the specified alist may or may not | |
4379 | be modified destructively, and the only safe way to update a variable | |
4380 | containing the alist is to @code{set!} it to the value that | |
4381 | @code{assq-remove!} and friends return. | |
4382 | ||
4383 | @example | |
4384 | address-list | |
4385 | @result{} | |
4386 | (("bob" . "11 Newington Avenue") ("mary" . "34 Elm Road") | |
4387 | ("james" . "1a London Road")) | |
4388 | ||
4389 | (set! address-list (assoc-remove! address-list "mary")) | |
4390 | address-list | |
4391 | @result{} | |
4392 | (("bob" . "11 Newington Avenue") ("james" . "1a London Road")) | |
4393 | @end example | |
4394 | ||
4395 | Note that, when @code{assq/v/oc-remove!} is used to modify an | |
4396 | association list that has been constructed only using the corresponding | |
4397 | @code{assq/v/oc-set!}, there can be at most one matching entry in the | |
4398 | alist, so the question of multiple entries being removed in one go does | |
4399 | not arise. If @code{assq/v/oc-remove!} is applied to an association | |
4400 | list that has been constructed using @code{acons}, or an | |
4401 | @code{assq/v/oc-set!} with a different level of equality, or any mixture | |
4402 | of these, it removes only the first matching entry from the alist, even | |
4403 | if the alist might contain further matching entries. For example: | |
4404 | ||
4405 | @example | |
4406 | (define address-list '()) | |
4407 | (set! address-list (assq-set! address-list "mary" "11 Elm Street")) | |
4408 | (set! address-list (assq-set! address-list "mary" "57 Pine Drive")) | |
4409 | address-list | |
4410 | @result{} | |
4411 | (("mary" . "57 Pine Drive") ("mary" . "11 Elm Street")) | |
4412 | ||
4413 | (set! address-list (assoc-remove! address-list "mary")) | |
4414 | address-list | |
4415 | @result{} | |
4416 | (("mary" . "11 Elm Street")) | |
4417 | @end example | |
4418 | ||
4419 | In this example, the two instances of the string "mary" are not the same | |
4420 | when compared using @code{eq?}, so the two @code{assq-set!} calls add | |
4421 | two distinct entries to @code{address-list}. When compared using | |
4422 | @code{equal?}, both "mary"s in @code{address-list} are the same as the | |
4423 | "mary" in the @code{assoc-remove!} call, but @code{assoc-remove!} stops | |
4424 | after removing the first matching entry that it finds, and so one of the | |
4425 | "mary" entries is left in place. | |
4426 | ||
4427 | @c docstring begin (texi-doc-string "guile" "assq-remove!") | |
4428 | @c docstring begin (texi-doc-string "guile" "assv-remove!") | |
4429 | @c docstring begin (texi-doc-string "guile" "assoc-remove!") | |
4430 | @deffn primitive assq-remove! alist key | |
4431 | @deffnx primitive assv-remove! alist key | |
4432 | @deffnx primitive assoc-remove! alist key | |
4433 | Delete the first entry in @var{alist} associated with @var{key}, and return | |
4434 | the resulting alist. | |
4435 | @end deffn | |
4436 | ||
4437 | @node Sloppy Alist Functions | |
4438 | @subsubsection Sloppy Alist Functions | |
38a93523 NJ |
4439 | |
4440 | @code{sloppy-assq}, @code{sloppy-assv} and @code{sloppy-assoc} behave | |
4441 | like the corresponding non-@code{sloppy-} procedures, except that they | |
4442 | return @code{#f} when the specified association list is not well-formed, | |
4443 | where the non-@code{sloppy-} versions would signal an error. | |
4444 | ||
4445 | Specifically, there are two conditions for which the non-@code{sloppy-} | |
4446 | procedures signal an error, which the @code{sloppy-} procedures handle | |
4447 | instead by returning @code{#f}. Firstly, if the specified alist as a | |
4448 | whole is not a proper list: | |
4449 | ||
4450 | @example | |
4451 | (assoc "mary" '((1 . 2) ("key" . "door") . "open sesame")) | |
4452 | @result{} | |
4453 | ERROR: In procedure assoc in expression (assoc "mary" (quote #)): | |
4454 | ERROR: Wrong type argument in position 2 (expecting NULLP): "open sesame" | |
4455 | ABORT: (wrong-type-arg) | |
4456 | ||
4457 | (sloppy-assoc "mary" '((1 . 2) ("key" . "door") . "open sesame")) | |
4458 | @result{} | |
4459 | #f | |
4460 | @end example | |
4461 | ||
4462 | @noindent | |
4463 | Secondly, if one of the entries in the specified alist is not a pair: | |
4464 | ||
4465 | @example | |
4466 | (assoc 2 '((1 . 1) 2 (3 . 9))) | |
4467 | @result{} | |
4468 | ERROR: In procedure assoc in expression (assoc 2 (quote #)): | |
4469 | ERROR: Wrong type argument in position 2 (expecting CONSP): 2 | |
4470 | ABORT: (wrong-type-arg) | |
4471 | ||
4472 | (sloppy-assoc 2 '((1 . 1) 2 (3 . 9))) | |
4473 | @result{} | |
4474 | #f | |
4475 | @end example | |
4476 | ||
4477 | Unless you are explicitly working with badly formed association lists, | |
4478 | it is much safer to use the non-@code{sloppy-} procedures, because they | |
4479 | help to highlight coding and data errors that the @code{sloppy-} | |
4480 | versions would silently cover up. | |
4481 | ||
4482 | @c docstring begin (texi-doc-string "guile" "sloppy-assq") | |
4483 | @deffn primitive sloppy-assq key alist | |
4484 | Behaves like @code{assq} but does not do any error checking. | |
4485 | Recommended only for use in Guile internals. | |
4486 | @end deffn | |
4487 | ||
4488 | @c docstring begin (texi-doc-string "guile" "sloppy-assv") | |
4489 | @deffn primitive sloppy-assv key alist | |
4490 | Behaves like @code{assv} but does not do any error checking. | |
4491 | Recommended only for use in Guile internals. | |
4492 | @end deffn | |
4493 | ||
4494 | @c docstring begin (texi-doc-string "guile" "sloppy-assoc") | |
4495 | @deffn primitive sloppy-assoc key alist | |
4496 | Behaves like @code{assoc} but does not do any error checking. | |
4497 | Recommended only for use in Guile internals. | |
4498 | @end deffn | |
4499 | ||
4500 | @node Alist Example | |
4501 | @subsubsection Alist Example | |
4502 | ||
4503 | Here is a longer example of how alists may be used in practice. | |
4504 | ||
4505 | @lisp | |
4506 | (define capitals '(("New York" . "Albany") | |
4507 | ("Oregon" . "Salem") | |
4508 | ("Florida" . "Miami"))) | |
4509 | ||
4510 | ;; What's the capital of Oregon? | |
4511 | (assoc "Oregon" capitals) @result{} ("Oregon" . "Salem") | |
4512 | (assoc-ref capitals "Oregon") @result{} "Salem" | |
4513 | ||
4514 | ;; We left out South Dakota. | |
4515 | (set! capitals | |
4516 | (assoc-set! capitals "South Dakota" "Bismarck")) | |
4517 | capitals | |
4518 | @result{} (("South Dakota" . "Bismarck") | |
4519 | ("New York" . "Albany") | |
4520 | ("Oregon" . "Salem") | |
4521 | ("Florida" . "Miami")) | |
4522 | ||
4523 | ;; And we got Florida wrong. | |
4524 | (set! capitals | |
4525 | (assoc-set! capitals "Florida" "Tallahassee")) | |
4526 | capitals | |
4527 | @result{} (("South Dakota" . "Bismarck") | |
4528 | ("New York" . "Albany") | |
4529 | ("Oregon" . "Salem") | |
4530 | ("Florida" . "Tallahassee")) | |
4531 | ||
4532 | ;; After Oregon secedes, we can remove it. | |
4533 | (set! capitals | |
4534 | (assoc-remove! capitals "Oregon")) | |
4535 | capitals | |
4536 | @result{} (("South Dakota" . "Bismarck") | |
4537 | ("New York" . "Albany") | |
4538 | ("Florida" . "Tallahassee")) | |
4539 | @end lisp | |
4540 | ||
4541 | @node Hash Tables | |
4542 | @subsection Hash Tables | |
4543 | ||
4544 | Like the association list functions, the hash table functions come | |
4545 | in several varieties: @code{hashq}, @code{hashv}, and @code{hash}. | |
4546 | The @code{hashq} functions use @code{eq?} to determine whether two | |
4547 | keys match. The @code{hashv} functions use @code{eqv?}, and the | |
4548 | @code{hash} functions use @code{equal?}. | |
4549 | ||
4550 | In each of the functions that follow, the @var{table} argument | |
4551 | must be a vector. The @var{key} and @var{value} arguments may be | |
4552 | any Scheme object. | |
4553 | ||
4554 | @c ARGFIXME obj/key | |
4555 | @c docstring begin (texi-doc-string "guile" "hashq-ref") | |
4556 | @deffn primitive hashq-ref table obj [dflt] | |
4557 | Look up @var{key} in the hash table @var{table}, and return the | |
4558 | value (if any) associated with it. If @var{key} is not found, | |
780ee65e NJ |
4559 | return @var{default} (or @code{#f} if no @var{default} argument |
4560 | is supplied). Uses @code{eq?} for equality testing. | |
38a93523 NJ |
4561 | @end deffn |
4562 | ||
4563 | @c ARGFIXME obj/key | |
4564 | @c docstring begin (texi-doc-string "guile" "hashv-ref") | |
4565 | @deffn primitive hashv-ref table obj [dflt] | |
4566 | Look up @var{key} in the hash table @var{table}, and return the | |
4567 | value (if any) associated with it. If @var{key} is not found, | |
780ee65e NJ |
4568 | return @var{default} (or @code{#f} if no @var{default} argument |
4569 | is supplied). Uses @code{eqv?} for equality testing. | |
38a93523 NJ |
4570 | @end deffn |
4571 | ||
4572 | @c ARGFIXME obj/key | |
4573 | @c docstring begin (texi-doc-string "guile" "hash-ref") | |
4574 | @deffn primitive hash-ref table obj [dflt] | |
4575 | Look up @var{key} in the hash table @var{table}, and return the | |
4576 | value (if any) associated with it. If @var{key} is not found, | |
780ee65e NJ |
4577 | return @var{default} (or @code{#f} if no @var{default} argument |
4578 | is supplied). Uses @code{equal?} for equality testing. | |
38a93523 NJ |
4579 | @end deffn |
4580 | ||
4581 | @c ARGFIXME obj/key | |
4582 | @c docstring begin (texi-doc-string "guile" "hashq-set!") | |
4583 | @deffn primitive hashq-set! table obj val | |
780ee65e NJ |
4584 | Find the entry in @var{table} associated with @var{key}, and |
4585 | store @var{value} there. Uses @code{eq?} for equality testing. | |
38a93523 NJ |
4586 | @end deffn |
4587 | ||
4588 | @c ARGFIXME obj/key | |
4589 | @c docstring begin (texi-doc-string "guile" "hashv-set!") | |
4590 | @deffn primitive hashv-set! table obj val | |
780ee65e NJ |
4591 | Find the entry in @var{table} associated with @var{key}, and |
4592 | store @var{value} there. Uses @code{eqv?} for equality testing. | |
38a93523 NJ |
4593 | @end deffn |
4594 | ||
4595 | @c ARGFIXME obj/key | |
4596 | @c docstring begin (texi-doc-string "guile" "hash-set!") | |
4597 | @deffn primitive hash-set! table obj val | |
780ee65e NJ |
4598 | Find the entry in @var{table} associated with @var{key}, and |
4599 | store @var{value} there. Uses @code{equal?} for equality | |
4600 | testing. | |
38a93523 NJ |
4601 | @end deffn |
4602 | ||
4603 | @c ARGFIXME obj/key | |
4604 | @c docstring begin (texi-doc-string "guile" "hashq-remove!") | |
4605 | @deffn primitive hashq-remove! table obj | |
780ee65e NJ |
4606 | Remove @var{key} (and any value associated with it) from |
4607 | @var{table}. Uses @code{eq?} for equality tests. | |
38a93523 NJ |
4608 | @end deffn |
4609 | ||
4610 | @c ARGFIXME obj/key | |
4611 | @c docstring begin (texi-doc-string "guile" "hashv-remove!") | |
4612 | @deffn primitive hashv-remove! table obj | |
780ee65e NJ |
4613 | Remove @var{key} (and any value associated with it) from |
4614 | @var{table}. Uses @code{eqv?} for equality tests. | |
38a93523 NJ |
4615 | @end deffn |
4616 | ||
4617 | @c ARGFIXME obj/key | |
4618 | @c docstring begin (texi-doc-string "guile" "hash-remove!") | |
4619 | @deffn primitive hash-remove! table obj | |
780ee65e NJ |
4620 | Remove @var{key} (and any value associated with it) from |
4621 | @var{table}. Uses @code{equal?} for equality tests. | |
38a93523 NJ |
4622 | @end deffn |
4623 | ||
4624 | The standard hash table functions may be too limited for some | |
4625 | applications. For example, you may want a hash table to store | |
4626 | strings in a case-insensitive manner, so that references to keys | |
4627 | named ``foobar'', ``FOOBAR'' and ``FooBaR'' will all yield the | |
4628 | same item. Guile provides you with @dfn{extended} hash tables | |
4629 | that permit you to specify a hash function and associator function | |
4630 | of your choosing. The functions described in the rest of this section | |
4631 | can be used to implement such custom hash table structures. | |
4632 | ||
4633 | If you are unfamiliar with the inner workings of hash tables, then | |
4634 | this facility will probably be a little too abstract for you to | |
4635 | use comfortably. If you are interested in learning more, see an | |
4636 | introductory textbook on data structures or algorithms for an | |
4637 | explanation of how hash tables are implemented. | |
4638 | ||
4639 | @c docstring begin (texi-doc-string "guile" "hashq") | |
4640 | @deffn primitive hashq key size | |
780ee65e NJ |
4641 | Determine a hash value for @var{key} that is suitable for |
4642 | lookups in a hashtable of size @var{size}, where @code{eq?} is | |
4643 | used as the equality predicate. The function returns an | |
4644 | integer in the range 0 to @var{size} - 1. Note that | |
4645 | @code{hashq} may use internal addresses. Thus two calls to | |
4646 | hashq where the keys are @code{eq?} are not guaranteed to | |
4647 | deliver the same value if the key object gets garbage collected | |
4648 | in between. This can happen, for example with symbols: | |
4649 | @code{(hashq 'foo n) (gc) (hashq 'foo n)} may produce two | |
4650 | different values, since @code{foo} will be garbage collected. | |
38a93523 NJ |
4651 | @end deffn |
4652 | ||
4653 | @c docstring begin (texi-doc-string "guile" "hashv") | |
4654 | @deffn primitive hashv key size | |
780ee65e NJ |
4655 | Determine a hash value for @var{key} that is suitable for |
4656 | lookups in a hashtable of size @var{size}, where @code{eqv?} is | |
4657 | used as the equality predicate. The function returns an | |
4658 | integer in the range 0 to @var{size} - 1. Note that | |
4659 | @code{(hashv key)} may use internal addresses. Thus two calls | |
4660 | to hashv where the keys are @code{eqv?} are not guaranteed to | |
4661 | deliver the same value if the key object gets garbage collected | |
4662 | in between. This can happen, for example with symbols: | |
4663 | @code{(hashv 'foo n) (gc) (hashv 'foo n)} may produce two | |
4664 | different values, since @code{foo} will be garbage collected. | |
38a93523 NJ |
4665 | @end deffn |
4666 | ||
4667 | @c docstring begin (texi-doc-string "guile" "hash") | |
4668 | @deffn primitive hash key size | |
780ee65e NJ |
4669 | Determine a hash value for @var{key} that is suitable for |
4670 | lookups in a hashtable of size @var{size}, where @code{equal?} | |
4671 | is used as the equality predicate. The function returns an | |
4672 | integer in the range 0 to @var{size} - 1. | |
38a93523 NJ |
4673 | @end deffn |
4674 | ||
4675 | @c ARGFIXME hash/hasher | |
4676 | @c docstring begin (texi-doc-string "guile" "hashx-ref") | |
4677 | @deffn primitive hashx-ref hash assoc table obj [dflt] | |
4678 | This behaves the same way as the corresponding @code{ref} | |
4679 | function, but uses @var{hasher} as a | |
4680 | hash function and @var{assoc} to compare keys. @code{hasher} must | |
4681 | be a function that takes two arguments, a key to be hashed and a | |
4682 | table size. @code{assoc} must be an associator function, like | |
4683 | @code{assoc}, @code{assq} or @code{assv}. | |
4684 | ||
4685 | By way of illustration, @code{hashq-ref table key} is equivalent | |
4686 | to @code{hashx-ref hashq assq table key}. | |
4687 | @end deffn | |
4688 | ||
4689 | @c docstring begin (texi-doc-string "guile" "hashx-set!") | |
4690 | @deffn primitive hashx-set! hash assoc table obj val | |
4691 | This behaves the same way as the corresponding @code{set!} | |
4692 | function, but uses @var{hasher} as a | |
4693 | hash function and @var{assoc} to compare keys. @code{hasher} must | |
4694 | be a function that takes two arguments, a key to be hashed and a | |
4695 | table size. @code{assoc} must be an associator function, like | |
4696 | @code{assoc}, @code{assq} or @code{assv}. | |
4697 | ||
4698 | By way of illustration, @code{hashq-set! table key} is equivalent | |
4699 | to @code{hashx-set! hashq assq table key}. | |
4700 | @end deffn | |
4701 | ||
4702 | @c docstring begin (texi-doc-string "guile" "hashq-get-handle") | |
4703 | @deffn primitive hashq-get-handle table obj | |
4704 | This procedure is similar to its @code{-ref} cousin, but returns a | |
4705 | @dfn{handle} from the hash table rather than the value associated with | |
4706 | @var{key}. By convention, a handle in a hash table is the pair which | |
4707 | associates a key with a value. Where @code{hashq-ref table key} returns | |
4708 | only a @code{value}, @code{hashq-get-handle table key} returns the pair | |
4709 | @code{(key . value)}. | |
4710 | @end deffn | |
4711 | ||
4712 | @c docstring begin (texi-doc-string "guile" "hashv-get-handle") | |
4713 | @deffn primitive hashv-get-handle table obj | |
4714 | This procedure is similar to its @code{-ref} cousin, but returns a | |
4715 | @dfn{handle} from the hash table rather than the value associated with | |
4716 | @var{key}. By convention, a handle in a hash table is the pair which | |
4717 | associates a key with a value. Where @code{hashv-ref table key} returns | |
4718 | only a @code{value}, @code{hashv-get-handle table key} returns the pair | |
4719 | @code{(key . value)}. | |
4720 | @end deffn | |
4721 | ||
4722 | @c docstring begin (texi-doc-string "guile" "hash-get-handle") | |
4723 | @deffn primitive hash-get-handle table obj | |
4724 | This procedure is similar to its @code{-ref} cousin, but returns a | |
4725 | @dfn{handle} from the hash table rather than the value associated with | |
4726 | @var{key}. By convention, a handle in a hash table is the pair which | |
4727 | associates a key with a value. Where @code{hash-ref table key} returns | |
4728 | only a @code{value}, @code{hash-get-handle table key} returns the pair | |
4729 | @code{(key . value)}. | |
4730 | @end deffn | |
4731 | ||
4732 | @c docstring begin (texi-doc-string "guile" "hashx-get-handle") | |
4733 | @deffn primitive hashx-get-handle hash assoc table obj | |
4734 | This behaves the same way as the corresponding @code{-get-handle} | |
4735 | function, but uses @var{hasher} as a | |
4736 | hash function and @var{assoc} to compare keys. @code{hasher} must | |
4737 | be a function that takes two arguments, a key to be hashed and a | |
4738 | table size. @code{assoc} must be an associator function, like | |
4739 | @code{assoc}, @code{assq} or @code{assv}. | |
4740 | @end deffn | |
4741 | ||
4742 | @c docstring begin (texi-doc-string "guile" "hashq-create-handle!") | |
4743 | @deffn primitive hashq-create-handle! table key init | |
4744 | This function looks up @var{key} in @var{table} and returns its handle. | |
4745 | If @var{key} is not already present, a new handle is created which | |
4746 | associates @var{key} with @var{init}. | |
4747 | @end deffn | |
4748 | ||
4749 | @c docstring begin (texi-doc-string "guile" "hashv-create-handle!") | |
4750 | @deffn primitive hashv-create-handle! table key init | |
4751 | This function looks up @var{key} in @var{table} and returns its handle. | |
4752 | If @var{key} is not already present, a new handle is created which | |
4753 | associates @var{key} with @var{init}. | |
4754 | @end deffn | |
4755 | ||
4756 | @c docstring begin (texi-doc-string "guile" "hash-create-handle!") | |
4757 | @deffn primitive hash-create-handle! table key init | |
4758 | This function looks up @var{key} in @var{table} and returns its handle. | |
4759 | If @var{key} is not already present, a new handle is created which | |
4760 | associates @var{key} with @var{init}. | |
4761 | @end deffn | |
4762 | ||
4763 | @c docstring begin (texi-doc-string "guile" "hashx-create-handle!") | |
4764 | @deffn primitive hashx-create-handle! hash assoc table obj init | |
4765 | This behaves the same way as the corresponding @code{-create-handle} | |
4766 | function, but uses @var{hasher} as a | |
4767 | hash function and @var{assoc} to compare keys. @code{hasher} must | |
4768 | be a function that takes two arguments, a key to be hashed and a | |
4769 | table size. @code{assoc} must be an associator function, like | |
4770 | @code{assoc}, @code{assq} or @code{assv}. | |
4771 | @end deffn | |
4772 | ||
4773 | @c docstring begin (texi-doc-string "guile" "hash-fold") | |
4774 | @deffn primitive hash-fold proc init table | |
4775 | An iterator over hash-table elements. | |
4776 | Accumulates and returns a result by applying PROC successively. | |
4777 | The arguments to PROC are "(key value prior-result)" where key | |
4778 | and value are successive pairs from the hash table TABLE, and | |
4779 | prior-result is either INIT (for the first application of PROC) | |
4780 | or the return value of the previous application of PROC. | |
4781 | For example, @code{(hash-fold acons () tab)} will convert a hash | |
4782 | table into an a-list of key-value pairs. | |
4783 | @end deffn | |
4784 | ||
4785 | ||
4786 | @node Vectors | |
4787 | @section Vectors | |
4788 | ||
fcaedf99 | 4789 | @r5index make-vector |
38a93523 NJ |
4790 | @c docstring begin (texi-doc-string "guile" "make-vector") |
4791 | @deffn primitive make-vector k [fill] | |
4792 | Returns a newly allocated vector of @var{k} elements. If a second | |
4793 | argument is given, then each element is initialized to @var{fill}. | |
4794 | Otherwise the initial contents of each element is unspecified. (r5rs) | |
4795 | @end deffn | |
4796 | ||
fcaedf99 MG |
4797 | @r5index vector |
4798 | @r5index list->vector | |
38a93523 NJ |
4799 | @c docstring begin (texi-doc-string "guile" "vector") |
4800 | @c docstring begin (texi-doc-string "guile" "list->vector") | |
4801 | @deffn primitive vector . l | |
4802 | @deffnx primitive list->vector l | |
780ee65e NJ |
4803 | Returns a newly allocated vector whose elements contain the |
4804 | given arguments. Analogous to @code{list}. (r5rs) | |
38a93523 | 4805 | |
780ee65e NJ |
4806 | @lisp |
4807 | (vector 'a 'b 'c) @result{} #(a b c) | |
4808 | @end lisp | |
38a93523 NJ |
4809 | @end deffn |
4810 | ||
fcaedf99 | 4811 | @r5index vector->list |
38a93523 NJ |
4812 | @c docstring begin (texi-doc-string "guile" "vector->list") |
4813 | @deffn primitive vector->list v | |
780ee65e NJ |
4814 | @samp{Vector->list} returns a newly allocated list of the |
4815 | objects contained in the elements of @var{vector}. (r5rs) | |
38a93523 | 4816 | |
780ee65e NJ |
4817 | @lisp |
4818 | (vector->list '#(dah dah didah)) @result{} (dah dah didah) | |
4819 | (list->vector '(dididit dah)) @result{} #(dididit dah) | |
4820 | @end lisp | |
38a93523 NJ |
4821 | @end deffn |
4822 | ||
fcaedf99 MG |
4823 | @r5index vector-fill! |
4824 | @c FIXME::martin: Argument names | |
38a93523 NJ |
4825 | @c docstring begin (texi-doc-string "guile" "vector-fill!") |
4826 | @deffn primitive vector-fill! v fill_x | |
4827 | Stores @var{fill} in every element of @var{vector}. | |
780ee65e | 4828 | The value returned by @code{vector-fill!} is unspecified. (r5rs) |
38a93523 NJ |
4829 | @end deffn |
4830 | ||
fcaedf99 | 4831 | @r5index vector? |
38a93523 NJ |
4832 | @c docstring begin (texi-doc-string "guile" "vector?") |
4833 | @deffn primitive vector? obj | |
780ee65e NJ |
4834 | Returns @code{#t} if @var{obj} is a vector, otherwise returns |
4835 | @code{#f}. (r5rs) | |
38a93523 NJ |
4836 | @end deffn |
4837 | ||
fcaedf99 MG |
4838 | @r5index vector-length |
4839 | @deffn primitive vector-length vector | |
4840 | Returns the number of elements in @var{vector} as an exact integer. | |
4841 | @end deffn | |
4842 | ||
4843 | @r5index vector-ref | |
4844 | @deffn primitive vector-ref vector k | |
4845 | @var{k} must be a valid index of @var{vector}. | |
4846 | @samp{Vector-ref} returns the contents of element @var{k} of | |
4847 | @var{vector}. | |
4848 | @lisp | |
4849 | (vector-ref '#(1 1 2 3 5 8 13 21) 5) @result{} 8 | |
4850 | (vector-ref '#(1 1 2 3 5 8 13 21) | |
4851 | (let ((i (round (* 2 (acos -1))))) | |
4852 | (if (inexact? i) | |
4853 | (inexact->exact i) | |
4854 | i))) @result{} 13 | |
4855 | @end lisp | |
4856 | @end deffn | |
4857 | ||
4858 | @r5index vector-set! | |
4859 | @deffn primitive vector-set! vector k obj | |
4860 | @var{k} must be a valid index of @var{vector}. | |
4861 | @code{Vector-set!} stores @var{obj} in element @var{k} of @var{vector}. | |
4862 | The value returned by @samp{vector-set!} is unspecified. | |
4863 | @lisp | |
4864 | (let ((vec (vector 0 '(2 2 2 2) "Anna"))) | |
4865 | (vector-set! vec 1 '("Sue" "Sue")) | |
4866 | vec) @result{} #(0 ("Sue" "Sue") "Anna") | |
4867 | (vector-set! '#(0 1 2) 1 "doe") @result{} @emph{error} ; constant vector | |
4868 | @end lisp | |
4869 | @end deffn | |
38a93523 NJ |
4870 | |
4871 | @node Hooks | |
4872 | @section Hooks | |
4873 | ||
4874 | @c docstring begin (texi-doc-string "guile" "make-hook-with-name") | |
4875 | @deffn primitive make-hook-with-name name [n_args] | |
4876 | Create a named hook with the name @var{name} for storing | |
4877 | procedures of arity @var{n_args}. | |
4878 | @end deffn | |
4879 | ||
4880 | @c docstring begin (texi-doc-string "guile" "make-hook") | |
4881 | @deffn primitive make-hook [n_args] | |
4882 | Create a hook for storing procedure of arity @var{n_args}. | |
4883 | @end deffn | |
4884 | ||
4885 | @c docstring begin (texi-doc-string "guile" "hook?") | |
4886 | @deffn primitive hook? x | |
4887 | Return @code{#t} if @var{x} is a hook. | |
4888 | @end deffn | |
4889 | ||
4890 | @c docstring begin (texi-doc-string "guile" "hook-empty?") | |
4891 | @deffn primitive hook-empty? hook | |
4892 | Return @code{#t} if @var{hook} is an empty hook. | |
4893 | @end deffn | |
4894 | ||
4895 | @c docstring begin (texi-doc-string "guile" "add-hook!") | |
4896 | @deffn primitive add-hook! hook proc [append_p] | |
4897 | Add the procedure @var{proc} to the hook @var{hook}. The | |
4898 | procedure is added to the end if @var{append_p} is true, | |
4899 | otherwise it is added to the front. | |
4900 | @end deffn | |
4901 | ||
4902 | @c docstring begin (texi-doc-string "guile" "remove-hook!") | |
4903 | @deffn primitive remove-hook! hook proc | |
4904 | Remove the procedure @var{proc} from the hook @var{hook}. | |
4905 | @end deffn | |
4906 | ||
4907 | @c docstring begin (texi-doc-string "guile" "reset-hook!") | |
4908 | @deffn primitive reset-hook! hook | |
4909 | Remove all procedures from the hook @var{hook}. | |
4910 | @end deffn | |
4911 | ||
4912 | @c docstring begin (texi-doc-string "guile" "run-hook") | |
4913 | @deffn primitive run-hook hook . args | |
4914 | Apply all procedures from the hook @var{hook} to the arguments | |
4915 | @var{args}. | |
4916 | @end deffn | |
4917 | ||
4918 | @c docstring begin (texi-doc-string "guile" "hook->list") | |
4919 | @deffn primitive hook->list hook | |
4920 | Convert the procedure list of @var{hook} to a list. | |
4921 | @end deffn | |
4922 | ||
4923 | ||
4924 | @node Other Data Types | |
4925 | @section Other Core Guile Data Types | |
4926 | ||
4927 | ||
4928 | @c Local Variables: | |
4929 | @c TeX-master: "guile.texi" | |
4930 | @c End: |