2 @c This is part of the GNU Guile Reference Manual.
3 @c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009
4 @c Free Software Foundation, Inc.
5 @c See the file guile.texi for copying conditions.
8 @node Compound Data Types
9 @section Compound Data Types
11 This chapter describes Guile's compound data types. By @dfn{compound}
12 we mean that the primary purpose of these data types is to act as
13 containers for other kinds of data (including other compound objects).
14 For instance, a (non-uniform) vector with length 5 is a container that
15 can hold five arbitrary Scheme objects.
17 The various kinds of container object differ from each other in how
18 their memory is allocated, how they are indexed, and how particular
19 values can be looked up within them.
22 * Pairs:: Scheme's basic building block.
23 * Lists:: Special list functions supported by Guile.
24 * Vectors:: One-dimensional arrays of Scheme objects.
25 * Uniform Numeric Vectors:: Vectors with elements of a single numeric type.
26 * Bit Vectors:: Vectors of bits.
27 * Generalized Vectors:: Treating all vector-like things uniformly.
28 * Arrays:: Matrices, etc.
31 * Dictionary Types:: About dictionary types in general.
32 * Association Lists:: List-based dictionaries.
33 * Hash Tables:: Table-based dictionaries.
41 Pairs are used to combine two Scheme objects into one compound object.
42 Hence the name: A pair stores a pair of objects.
44 The data type @dfn{pair} is extremely important in Scheme, just like in
45 any other Lisp dialect. The reason is that pairs are not only used to
46 make two values available as one object, but that pairs are used for
47 constructing lists of values. Because lists are so important in Scheme,
48 they are described in a section of their own (@pxref{Lists}).
50 Pairs can literally get entered in source code or at the REPL, in the
51 so-called @dfn{dotted list} syntax. This syntax consists of an opening
52 parentheses, the first element of the pair, a dot, the second element
53 and a closing parentheses. The following example shows how a pair
54 consisting of the two numbers 1 and 2, and a pair containing the symbols
55 @code{foo} and @code{bar} can be entered. It is very important to write
56 the whitespace before and after the dot, because otherwise the Scheme
57 parser would not be able to figure out where to split the tokens.
64 But beware, if you want to try out these examples, you have to
65 @dfn{quote} the expressions. More information about quotation is
66 available in the section @ref{Expression Syntax}. The correct way
67 to try these examples is as follows.
78 A new pair is made by calling the procedure @code{cons} with two
79 arguments. Then the argument values are stored into a newly allocated
80 pair, and the pair is returned. The name @code{cons} stands for
81 "construct". Use the procedure @code{pair?} to test whether a
82 given Scheme object is a pair or not.
85 @deffn {Scheme Procedure} cons x y
86 @deffnx {C Function} scm_cons (x, y)
87 Return a newly allocated pair whose car is @var{x} and whose
88 cdr is @var{y}. The pair is guaranteed to be different (in the
89 sense of @code{eq?}) from every previously existing object.
93 @deffn {Scheme Procedure} pair? x
94 @deffnx {C Function} scm_pair_p (x)
95 Return @code{#t} if @var{x} is a pair; otherwise return
99 @deftypefn {C Function} int scm_is_pair (SCM x)
100 Return 1 when @var{x} is a pair; otherwise return 0.
103 The two parts of a pair are traditionally called @dfn{car} and
104 @dfn{cdr}. They can be retrieved with procedures of the same name
105 (@code{car} and @code{cdr}), and can be modified with the procedures
106 @code{set-car!} and @code{set-cdr!}. Since a very common operation in
107 Scheme programs is to access the car of a car of a pair, or the car of
108 the cdr of a pair, etc., the procedures called @code{caar},
109 @code{cadr} and so on are also predefined.
113 @deffn {Scheme Procedure} car pair
114 @deffnx {Scheme Procedure} cdr pair
115 @deffnx {C Function} scm_car (pair)
116 @deffnx {C Function} scm_cdr (pair)
117 Return the car or the cdr of @var{pair}, respectively.
120 @deftypefn {C Macro} SCM SCM_CAR (SCM pair)
121 @deftypefnx {C Macro} SCM SCM_CDR (SCM pair)
122 These two macros are the fastest way to access the car or cdr of a
123 pair; they can be thought of as compiling into a single memory
126 These macros do no checking at all. The argument @var{pair} must be a
130 @deffn {Scheme Procedure} cddr pair
131 @deffnx {Scheme Procedure} cdar pair
132 @deffnx {Scheme Procedure} cadr pair
133 @deffnx {Scheme Procedure} caar pair
134 @deffnx {Scheme Procedure} cdddr pair
135 @deffnx {Scheme Procedure} cddar pair
136 @deffnx {Scheme Procedure} cdadr pair
137 @deffnx {Scheme Procedure} cdaar pair
138 @deffnx {Scheme Procedure} caddr pair
139 @deffnx {Scheme Procedure} cadar pair
140 @deffnx {Scheme Procedure} caadr pair
141 @deffnx {Scheme Procedure} caaar pair
142 @deffnx {Scheme Procedure} cddddr pair
143 @deffnx {Scheme Procedure} cdddar pair
144 @deffnx {Scheme Procedure} cddadr pair
145 @deffnx {Scheme Procedure} cddaar pair
146 @deffnx {Scheme Procedure} cdaddr pair
147 @deffnx {Scheme Procedure} cdadar pair
148 @deffnx {Scheme Procedure} cdaadr pair
149 @deffnx {Scheme Procedure} cdaaar pair
150 @deffnx {Scheme Procedure} cadddr pair
151 @deffnx {Scheme Procedure} caddar pair
152 @deffnx {Scheme Procedure} cadadr pair
153 @deffnx {Scheme Procedure} cadaar pair
154 @deffnx {Scheme Procedure} caaddr pair
155 @deffnx {Scheme Procedure} caadar pair
156 @deffnx {Scheme Procedure} caaadr pair
157 @deffnx {Scheme Procedure} caaaar pair
158 @deffnx {C Function} scm_cddr (pair)
159 @deffnx {C Function} scm_cdar (pair)
160 @deffnx {C Function} scm_cadr (pair)
161 @deffnx {C Function} scm_caar (pair)
162 @deffnx {C Function} scm_cdddr (pair)
163 @deffnx {C Function} scm_cddar (pair)
164 @deffnx {C Function} scm_cdadr (pair)
165 @deffnx {C Function} scm_cdaar (pair)
166 @deffnx {C Function} scm_caddr (pair)
167 @deffnx {C Function} scm_cadar (pair)
168 @deffnx {C Function} scm_caadr (pair)
169 @deffnx {C Function} scm_caaar (pair)
170 @deffnx {C Function} scm_cddddr (pair)
171 @deffnx {C Function} scm_cdddar (pair)
172 @deffnx {C Function} scm_cddadr (pair)
173 @deffnx {C Function} scm_cddaar (pair)
174 @deffnx {C Function} scm_cdaddr (pair)
175 @deffnx {C Function} scm_cdadar (pair)
176 @deffnx {C Function} scm_cdaadr (pair)
177 @deffnx {C Function} scm_cdaaar (pair)
178 @deffnx {C Function} scm_cadddr (pair)
179 @deffnx {C Function} scm_caddar (pair)
180 @deffnx {C Function} scm_cadadr (pair)
181 @deffnx {C Function} scm_cadaar (pair)
182 @deffnx {C Function} scm_caaddr (pair)
183 @deffnx {C Function} scm_caadar (pair)
184 @deffnx {C Function} scm_caaadr (pair)
185 @deffnx {C Function} scm_caaaar (pair)
186 These procedures are compositions of @code{car} and @code{cdr}, where
187 for example @code{caddr} could be defined by
190 (define caddr (lambda (x) (car (cdr (cdr x)))))
193 @code{cadr}, @code{caddr} and @code{cadddr} pick out the second, third
194 or fourth elements of a list, respectively. SRFI-1 provides the same
195 under the names @code{second}, @code{third} and @code{fourth}
196 (@pxref{SRFI-1 Selectors}).
200 @deffn {Scheme Procedure} set-car! pair value
201 @deffnx {C Function} scm_set_car_x (pair, value)
202 Stores @var{value} in the car field of @var{pair}. The value returned
203 by @code{set-car!} is unspecified.
207 @deffn {Scheme Procedure} set-cdr! pair value
208 @deffnx {C Function} scm_set_cdr_x (pair, value)
209 Stores @var{value} in the cdr field of @var{pair}. The value returned
210 by @code{set-cdr!} is unspecified.
218 A very important data type in Scheme---as well as in all other Lisp
219 dialects---is the data type @dfn{list}.@footnote{Strictly speaking,
220 Scheme does not have a real datatype @dfn{list}. Lists are made up of
221 @dfn{chained pairs}, and only exist by definition---a list is a chain
222 of pairs which looks like a list.}
224 This is the short definition of what a list is:
228 Either the empty list @code{()},
231 or a pair which has a list in its cdr.
234 @c FIXME::martin: Describe the pair chaining in more detail.
236 @c FIXME::martin: What is a proper, what an improper list?
237 @c What is a circular list?
239 @c FIXME::martin: Maybe steal some graphics from the Elisp reference
243 * List Syntax:: Writing literal lists.
244 * List Predicates:: Testing lists.
245 * List Constructors:: Creating new lists.
246 * List Selection:: Selecting from lists, getting their length.
247 * Append/Reverse:: Appending and reversing lists.
248 * List Modification:: Modifying existing lists.
249 * List Searching:: Searching for list elements
250 * List Mapping:: Applying procedures to lists.
254 @subsubsection List Read Syntax
256 The syntax for lists is an opening parentheses, then all the elements of
257 the list (separated by whitespace) and finally a closing
258 parentheses.@footnote{Note that there is no separation character between
259 the list elements, like a comma or a semicolon.}.
262 (1 2 3) ; @r{a list of the numbers 1, 2 and 3}
263 ("foo" bar 3.1415) ; @r{a string, a symbol and a real number}
264 () ; @r{the empty list}
267 The last example needs a bit more explanation. A list with no elements,
268 called the @dfn{empty list}, is special in some ways. It is used for
269 terminating lists by storing it into the cdr of the last pair that makes
270 up a list. An example will clear that up:
281 This example also shows that lists have to be quoted when written
282 (@pxref{Expression Syntax}), because they would otherwise be
283 mistakingly taken as procedure applications (@pxref{Simple
287 @node List Predicates
288 @subsubsection List Predicates
290 Often it is useful to test whether a given Scheme object is a list or
291 not. List-processing procedures could use this information to test
292 whether their input is valid, or they could do different things
293 depending on the datatype of their arguments.
296 @deffn {Scheme Procedure} list? x
297 @deffnx {C Function} scm_list_p (x)
298 Return @code{#t} iff @var{x} is a proper list, else @code{#f}.
301 The predicate @code{null?} is often used in list-processing code to
302 tell whether a given list has run out of elements. That is, a loop
303 somehow deals with the elements of a list until the list satisfies
304 @code{null?}. Then, the algorithm terminates.
307 @deffn {Scheme Procedure} null? x
308 @deffnx {C Function} scm_null_p (x)
309 Return @code{#t} iff @var{x} is the empty list, else @code{#f}.
312 @deftypefn {C Function} int scm_is_null (SCM x)
313 Return 1 when @var{x} is the empty list; otherwise return 0.
317 @node List Constructors
318 @subsubsection List Constructors
320 This section describes the procedures for constructing new lists.
321 @code{list} simply returns a list where the elements are the arguments,
322 @code{cons*} is similar, but the last argument is stored in the cdr of
323 the last pair of the list.
325 @c C Function scm_list(rest) used to be documented here, but it's a
326 @c no-op since it does nothing but return the list the caller must
327 @c have already created.
329 @deffn {Scheme Procedure} list elem1 @dots{} elemN
330 @deffnx {C Function} scm_list_1 (elem1)
331 @deffnx {C Function} scm_list_2 (elem1, elem2)
332 @deffnx {C Function} scm_list_3 (elem1, elem2, elem3)
333 @deffnx {C Function} scm_list_4 (elem1, elem2, elem3, elem4)
334 @deffnx {C Function} scm_list_5 (elem1, elem2, elem3, elem4, elem5)
335 @deffnx {C Function} scm_list_n (elem1, @dots{}, elemN, @nicode{SCM_UNDEFINED})
337 Return a new list containing elements @var{elem1} to @var{elemN}.
339 @code{scm_list_n} takes a variable number of arguments, terminated by
340 the special @code{SCM_UNDEFINED}. That final @code{SCM_UNDEFINED} is
341 not included in the list. None of @var{elem1} to @var{elemN} can
342 themselves be @code{SCM_UNDEFINED}, or @code{scm_list_n} will
343 terminate at that point.
346 @c C Function scm_cons_star(arg1,rest) used to be documented here,
347 @c but it's not really a useful interface, since it expects the
348 @c caller to have already consed up all but the first argument
351 @deffn {Scheme Procedure} cons* arg1 arg2 @dots{}
352 Like @code{list}, but the last arg provides the tail of the
353 constructed list, returning @code{(cons @var{arg1} (cons
354 @var{arg2} (cons @dots{} @var{argn})))}. Requires at least one
355 argument. If given one argument, that argument is returned as
356 result. This function is called @code{list*} in some other
357 Schemes and in Common LISP.
360 @deffn {Scheme Procedure} list-copy lst
361 @deffnx {C Function} scm_list_copy (lst)
362 Return a (newly-created) copy of @var{lst}.
365 @deffn {Scheme Procedure} make-list n [init]
366 Create a list containing of @var{n} elements, where each element is
367 initialized to @var{init}. @var{init} defaults to the empty list
368 @code{()} if not given.
371 Note that @code{list-copy} only makes a copy of the pairs which make up
372 the spine of the lists. The list elements are not copied, which means
373 that modifying the elements of the new list also modifies the elements
374 of the old list. On the other hand, applying procedures like
375 @code{set-cdr!} or @code{delv!} to the new list will not alter the old
376 list. If you also need to copy the list elements (making a deep copy),
377 use the procedure @code{copy-tree} (@pxref{Copying}).
380 @subsubsection List Selection
382 These procedures are used to get some information about a list, or to
383 retrieve one or more elements of a list.
386 @deffn {Scheme Procedure} length lst
387 @deffnx {C Function} scm_length (lst)
388 Return the number of elements in list @var{lst}.
391 @deffn {Scheme Procedure} last-pair lst
392 @deffnx {C Function} scm_last_pair (lst)
393 Return the last pair in @var{lst}, signalling an error if
394 @var{lst} is circular.
398 @deffn {Scheme Procedure} list-ref list k
399 @deffnx {C Function} scm_list_ref (list, k)
400 Return the @var{k}th element from @var{list}.
404 @deffn {Scheme Procedure} list-tail lst k
405 @deffnx {Scheme Procedure} list-cdr-ref lst k
406 @deffnx {C Function} scm_list_tail (lst, k)
407 Return the "tail" of @var{lst} beginning with its @var{k}th element.
408 The first element of the list is considered to be element 0.
410 @code{list-tail} and @code{list-cdr-ref} are identical. It may help to
411 think of @code{list-cdr-ref} as accessing the @var{k}th cdr of the list,
412 or returning the results of cdring @var{k} times down @var{lst}.
415 @deffn {Scheme Procedure} list-head lst k
416 @deffnx {C Function} scm_list_head (lst, k)
417 Copy the first @var{k} elements from @var{lst} into a new list, and
422 @subsubsection Append and Reverse
424 @code{append} and @code{append!} are used to concatenate two or more
425 lists in order to form a new list. @code{reverse} and @code{reverse!}
426 return lists with the same elements as their arguments, but in reverse
427 order. The procedure variants with an @code{!} directly modify the
428 pairs which form the list, whereas the other procedures create new
429 pairs. This is why you should be careful when using the side-effecting
433 @deffn {Scheme Procedure} append lst1 @dots{} lstN
434 @deffnx {Scheme Procedure} append! lst1 @dots{} lstN
435 @deffnx {C Function} scm_append (lstlst)
436 @deffnx {C Function} scm_append_x (lstlst)
437 Return a list comprising all the elements of lists @var{lst1} to
441 (append '(x) '(y)) @result{} (x y)
442 (append '(a) '(b c d)) @result{} (a b c d)
443 (append '(a (b)) '((c))) @result{} (a (b) (c))
446 The last argument @var{lstN} may actually be any object; an improper
447 list results if the last argument is not a proper list.
450 (append '(a b) '(c . d)) @result{} (a b c . d)
451 (append '() 'a) @result{} a
454 @code{append} doesn't modify the given lists, but the return may share
455 structure with the final @var{lstN}. @code{append!} modifies the
456 given lists to form its return.
458 For @code{scm_append} and @code{scm_append_x}, @var{lstlst} is a list
459 of the list operands @var{lst1} @dots{} @var{lstN}. That @var{lstlst}
460 itself is not modified or used in the return.
464 @deffn {Scheme Procedure} reverse lst
465 @deffnx {Scheme Procedure} reverse! lst [newtail]
466 @deffnx {C Function} scm_reverse (lst)
467 @deffnx {C Function} scm_reverse_x (lst, newtail)
468 Return a list comprising the elements of @var{lst}, in reverse order.
470 @code{reverse} constructs a new list, @code{reverse!} modifies
471 @var{lst} in constructing its return.
473 For @code{reverse!}, the optional @var{newtail} is appended to the
474 result. @var{newtail} isn't reversed, it simply becomes the list
475 tail. For @code{scm_reverse_x}, the @var{newtail} parameter is
476 mandatory, but can be @code{SCM_EOL} if no further tail is required.
479 @node List Modification
480 @subsubsection List Modification
482 The following procedures modify an existing list, either by changing
483 elements of the list, or by changing the list structure itself.
485 @deffn {Scheme Procedure} list-set! list k val
486 @deffnx {C Function} scm_list_set_x (list, k, val)
487 Set the @var{k}th element of @var{list} to @var{val}.
490 @deffn {Scheme Procedure} list-cdr-set! list k val
491 @deffnx {C Function} scm_list_cdr_set_x (list, k, val)
492 Set the @var{k}th cdr of @var{list} to @var{val}.
495 @deffn {Scheme Procedure} delq item lst
496 @deffnx {C Function} scm_delq (item, lst)
497 Return a newly-created copy of @var{lst} with elements
498 @code{eq?} to @var{item} removed. This procedure mirrors
499 @code{memq}: @code{delq} compares elements of @var{lst} against
500 @var{item} with @code{eq?}.
503 @deffn {Scheme Procedure} delv item lst
504 @deffnx {C Function} scm_delv (item, lst)
505 Return a newly-created copy of @var{lst} with elements
506 @code{eqv?} to @var{item} removed. This procedure mirrors
507 @code{memv}: @code{delv} compares elements of @var{lst} against
508 @var{item} with @code{eqv?}.
511 @deffn {Scheme Procedure} delete item lst
512 @deffnx {C Function} scm_delete (item, lst)
513 Return a newly-created copy of @var{lst} with elements
514 @code{equal?} to @var{item} removed. This procedure mirrors
515 @code{member}: @code{delete} compares elements of @var{lst}
516 against @var{item} with @code{equal?}.
518 See also SRFI-1 which has an extended @code{delete} (@ref{SRFI-1
519 Deleting}), and also an @code{lset-difference} which can delete
520 multiple @var{item}s in one call (@ref{SRFI-1 Set Operations}).
523 @deffn {Scheme Procedure} delq! item lst
524 @deffnx {Scheme Procedure} delv! item lst
525 @deffnx {Scheme Procedure} delete! item lst
526 @deffnx {C Function} scm_delq_x (item, lst)
527 @deffnx {C Function} scm_delv_x (item, lst)
528 @deffnx {C Function} scm_delete_x (item, lst)
529 These procedures are destructive versions of @code{delq}, @code{delv}
530 and @code{delete}: they modify the pointers in the existing @var{lst}
531 rather than creating a new list. Caveat evaluator: Like other
532 destructive list functions, these functions cannot modify the binding of
533 @var{lst}, and so cannot be used to delete the first element of
534 @var{lst} destructively.
537 @deffn {Scheme Procedure} delq1! item lst
538 @deffnx {C Function} scm_delq1_x (item, lst)
539 Like @code{delq!}, but only deletes the first occurrence of
540 @var{item} from @var{lst}. Tests for equality using
541 @code{eq?}. See also @code{delv1!} and @code{delete1!}.
544 @deffn {Scheme Procedure} delv1! item lst
545 @deffnx {C Function} scm_delv1_x (item, lst)
546 Like @code{delv!}, but only deletes the first occurrence of
547 @var{item} from @var{lst}. Tests for equality using
548 @code{eqv?}. See also @code{delq1!} and @code{delete1!}.
551 @deffn {Scheme Procedure} delete1! item lst
552 @deffnx {C Function} scm_delete1_x (item, lst)
553 Like @code{delete!}, but only deletes the first occurrence of
554 @var{item} from @var{lst}. Tests for equality using
555 @code{equal?}. See also @code{delq1!} and @code{delv1!}.
558 @deffn {Scheme Procedure} filter pred lst
559 @deffnx {Scheme Procedure} filter! pred lst
560 Return a list containing all elements from @var{lst} which satisfy the
561 predicate @var{pred}. The elements in the result list have the same
562 order as in @var{lst}. The order in which @var{pred} is applied to
563 the list elements is not specified.
565 @code{filter} does not change @var{lst}, but the result may share a
566 tail with it. @code{filter!} may modify @var{lst} to construct its
571 @subsubsection List Searching
573 The following procedures search lists for particular elements. They use
574 different comparison predicates for comparing list elements with the
575 object to be searched. When they fail, they return @code{#f}, otherwise
576 they return the sublist whose car is equal to the search object, where
577 equality depends on the equality predicate used.
580 @deffn {Scheme Procedure} memq x lst
581 @deffnx {C Function} scm_memq (x, lst)
582 Return the first sublist of @var{lst} whose car is @code{eq?}
583 to @var{x} where the sublists of @var{lst} are the non-empty
584 lists returned by @code{(list-tail @var{lst} @var{k})} for
585 @var{k} less than the length of @var{lst}. If @var{x} does not
586 occur in @var{lst}, then @code{#f} (not the empty list) is
591 @deffn {Scheme Procedure} memv x lst
592 @deffnx {C Function} scm_memv (x, lst)
593 Return the first sublist of @var{lst} whose car is @code{eqv?}
594 to @var{x} where the sublists of @var{lst} are the non-empty
595 lists returned by @code{(list-tail @var{lst} @var{k})} for
596 @var{k} less than the length of @var{lst}. If @var{x} does not
597 occur in @var{lst}, then @code{#f} (not the empty list) is
602 @deffn {Scheme Procedure} member x lst
603 @deffnx {C Function} scm_member (x, lst)
604 Return the first sublist of @var{lst} whose car is
605 @code{equal?} to @var{x} where the sublists of @var{lst} are
606 the non-empty lists returned by @code{(list-tail @var{lst}
607 @var{k})} for @var{k} less than the length of @var{lst}. If
608 @var{x} does not occur in @var{lst}, then @code{#f} (not the
609 empty list) is returned.
611 See also SRFI-1 which has an extended @code{member} function
612 (@ref{SRFI-1 Searching}).
617 @subsubsection List Mapping
619 List processing is very convenient in Scheme because the process of
620 iterating over the elements of a list can be highly abstracted. The
621 procedures in this section are the most basic iterating procedures for
622 lists. They take a procedure and one or more lists as arguments, and
623 apply the procedure to each element of the list. They differ in their
627 @c begin (texi-doc-string "guile" "map")
628 @deffn {Scheme Procedure} map proc arg1 arg2 @dots{}
629 @deffnx {Scheme Procedure} map-in-order proc arg1 arg2 @dots{}
630 @deffnx {C Function} scm_map (proc, arg1, args)
631 Apply @var{proc} to each element of the list @var{arg1} (if only two
632 arguments are given), or to the corresponding elements of the argument
633 lists (if more than two arguments are given). The result(s) of the
634 procedure applications are saved and returned in a list. For
635 @code{map}, the order of procedure applications is not specified,
636 @code{map-in-order} applies the procedure from left to right to the list
641 @c begin (texi-doc-string "guile" "for-each")
642 @deffn {Scheme Procedure} for-each proc arg1 arg2 @dots{}
643 Like @code{map}, but the procedure is always applied from left to right,
644 and the result(s) of the procedure applications are thrown away. The
645 return value is not specified.
648 See also SRFI-1 which extends these functions to take lists of unequal
649 lengths (@ref{SRFI-1 Fold and Map}).
655 Vectors are sequences of Scheme objects. Unlike lists, the length of a
656 vector, once the vector is created, cannot be changed. The advantage of
657 vectors over lists is that the time required to access one element of a vector
658 given its @dfn{position} (synonymous with @dfn{index}), a zero-origin number,
659 is constant, whereas lists have an access time linear to the position of the
660 accessed element in the list.
662 Vectors can contain any kind of Scheme object; it is even possible to
663 have different types of objects in the same vector. For vectors
664 containing vectors, you may wish to use arrays, instead. Note, too,
665 that vectors are the special case of one dimensional non-uniform arrays
666 and that most array procedures operate happily on vectors
670 * Vector Syntax:: Read syntax for vectors.
671 * Vector Creation:: Dynamic vector creation and validation.
672 * Vector Accessors:: Accessing and modifying vector contents.
673 * Vector Accessing from C:: Ways to work with vectors from C.
678 @subsubsection Read Syntax for Vectors
680 Vectors can literally be entered in source code, just like strings,
681 characters or some of the other data types. The read syntax for vectors
682 is as follows: A sharp sign (@code{#}), followed by an opening
683 parentheses, all elements of the vector in their respective read syntax,
684 and finally a closing parentheses. The following are examples of the
685 read syntax for vectors; where the first vector only contains numbers
686 and the second three different object types: a string, a symbol and a
687 number in hexadecimal notation.
691 #("Hello" foo #xdeadbeef)
694 Like lists, vectors have to be quoted:
697 '#(a b c) @result{} #(a b c)
700 @node Vector Creation
701 @subsubsection Dynamic Vector Creation and Validation
703 Instead of creating a vector implicitly by using the read syntax just
704 described, you can create a vector dynamically by calling one of the
705 @code{vector} and @code{list->vector} primitives with the list of Scheme
706 values that you want to place into a vector. The size of the vector
707 thus created is determined implicitly by the number of arguments given.
710 @rnindex list->vector
711 @deffn {Scheme Procedure} vector . l
712 @deffnx {Scheme Procedure} list->vector l
713 @deffnx {C Function} scm_vector (l)
714 Return a newly allocated vector composed of the
715 given arguments. Analogous to @code{list}.
718 (vector 'a 'b 'c) @result{} #(a b c)
722 The inverse operation is @code{vector->list}:
724 @rnindex vector->list
725 @deffn {Scheme Procedure} vector->list v
726 @deffnx {C Function} scm_vector_to_list (v)
727 Return a newly allocated list composed of the elements of @var{v}.
730 (vector->list '#(dah dah didah)) @result{} (dah dah didah)
731 (list->vector '(dididit dah)) @result{} #(dididit dah)
735 To allocate a vector with an explicitly specified size, use
736 @code{make-vector}. With this primitive you can also specify an initial
737 value for the vector elements (the same value for all elements, that
741 @deffn {Scheme Procedure} make-vector len [fill]
742 @deffnx {C Function} scm_make_vector (len, fill)
743 Return a newly allocated vector of @var{len} elements. If a
744 second argument is given, then each position is initialized to
745 @var{fill}. Otherwise the initial contents of each position is
749 @deftypefn {C Function} SCM scm_c_make_vector (size_t k, SCM fill)
750 Like @code{scm_make_vector}, but the length is given as a @code{size_t}.
753 To check whether an arbitrary Scheme value @emph{is} a vector, use the
754 @code{vector?} primitive:
757 @deffn {Scheme Procedure} vector? obj
758 @deffnx {C Function} scm_vector_p (obj)
759 Return @code{#t} if @var{obj} is a vector, otherwise return
763 @deftypefn {C Function} int scm_is_vector (SCM obj)
764 Return non-zero when @var{obj} is a vector, otherwise return
768 @node Vector Accessors
769 @subsubsection Accessing and Modifying Vector Contents
771 @code{vector-length} and @code{vector-ref} return information about a
772 given vector, respectively its size and the elements that are contained
775 @rnindex vector-length
776 @deffn {Scheme Procedure} vector-length vector
777 @deffnx {C Function} scm_vector_length vector
778 Return the number of elements in @var{vector} as an exact integer.
781 @deftypefn {C Function} size_t scm_c_vector_length (SCM v)
782 Return the number of elements in @var{vector} as a @code{size_t}.
786 @deffn {Scheme Procedure} vector-ref vector k
787 @deffnx {C Function} scm_vector_ref vector k
788 Return the contents of position @var{k} of @var{vector}.
789 @var{k} must be a valid index of @var{vector}.
791 (vector-ref '#(1 1 2 3 5 8 13 21) 5) @result{} 8
792 (vector-ref '#(1 1 2 3 5 8 13 21)
793 (let ((i (round (* 2 (acos -1)))))
800 @deftypefn {C Function} SCM scm_c_vector_ref (SCM v, size_t k)
801 Return the contents of position @var{k} (a @code{size_t}) of
805 A vector created by one of the dynamic vector constructor procedures
806 (@pxref{Vector Creation}) can be modified using the following
809 @emph{NOTE:} According to R5RS, it is an error to use any of these
810 procedures on a literally read vector, because such vectors should be
811 considered as constants. Currently, however, Guile does not detect this
815 @deffn {Scheme Procedure} vector-set! vector k obj
816 @deffnx {C Function} scm_vector_set_x vector k obj
817 Store @var{obj} in position @var{k} of @var{vector}.
818 @var{k} must be a valid index of @var{vector}.
819 The value returned by @samp{vector-set!} is unspecified.
821 (let ((vec (vector 0 '(2 2 2 2) "Anna")))
822 (vector-set! vec 1 '("Sue" "Sue"))
823 vec) @result{} #(0 ("Sue" "Sue") "Anna")
827 @deftypefn {C Function} void scm_c_vector_set_x (SCM v, size_t k, SCM obj)
828 Store @var{obj} in position @var{k} (a @code{size_t}) of @var{v}.
831 @rnindex vector-fill!
832 @deffn {Scheme Procedure} vector-fill! v fill
833 @deffnx {C Function} scm_vector_fill_x (v, fill)
834 Store @var{fill} in every position of @var{vector}. The value
835 returned by @code{vector-fill!} is unspecified.
838 @deffn {Scheme Procedure} vector-copy vec
839 @deffnx {C Function} scm_vector_copy (vec)
840 Return a copy of @var{vec}.
843 @deffn {Scheme Procedure} vector-move-left! vec1 start1 end1 vec2 start2
844 @deffnx {C Function} scm_vector_move_left_x (vec1, start1, end1, vec2, start2)
845 Copy elements from @var{vec1}, positions @var{start1} to @var{end1},
846 to @var{vec2} starting at position @var{start2}. @var{start1} and
847 @var{start2} are inclusive indices; @var{end1} is exclusive.
849 @code{vector-move-left!} copies elements in leftmost order.
850 Therefore, in the case where @var{vec1} and @var{vec2} refer to the
851 same vector, @code{vector-move-left!} is usually appropriate when
852 @var{start1} is greater than @var{start2}.
855 @deffn {Scheme Procedure} vector-move-right! vec1 start1 end1 vec2 start2
856 @deffnx {C Function} scm_vector_move_right_x (vec1, start1, end1, vec2, start2)
857 Copy elements from @var{vec1}, positions @var{start1} to @var{end1},
858 to @var{vec2} starting at position @var{start2}. @var{start1} and
859 @var{start2} are inclusive indices; @var{end1} is exclusive.
861 @code{vector-move-right!} copies elements in rightmost order.
862 Therefore, in the case where @var{vec1} and @var{vec2} refer to the
863 same vector, @code{vector-move-right!} is usually appropriate when
864 @var{start1} is less than @var{start2}.
867 @node Vector Accessing from C
868 @subsubsection Vector Accessing from C
870 A vector can be read and modified from C with the functions
871 @code{scm_c_vector_ref} and @code{scm_c_vector_set_x}, for example. In
872 addition to these functions, there are two more ways to access vectors
873 from C that might be more efficient in certain situations: you can
874 restrict yourself to @dfn{simple vectors} and then use the very fast
875 @emph{simple vector macros}; or you can use the very general framework
876 for accessing all kinds of arrays (@pxref{Accessing Arrays from C}),
877 which is more verbose, but can deal efficiently with all kinds of
878 vectors (and arrays). For vectors, you can use the
879 @code{scm_vector_elements} and @code{scm_vector_writable_elements}
880 functions as shortcuts.
882 @deftypefn {C Function} int scm_is_simple_vector (SCM obj)
883 Return non-zero if @var{obj} is a simple vector, else return zero. A
884 simple vector is a vector that can be used with the @code{SCM_SIMPLE_*}
887 The following functions are guaranteed to return simple vectors:
888 @code{scm_make_vector}, @code{scm_c_make_vector}, @code{scm_vector},
889 @code{scm_list_to_vector}.
892 @deftypefn {C Macro} size_t SCM_SIMPLE_VECTOR_LENGTH (SCM vec)
893 Evaluates to the length of the simple vector @var{vec}. No type
897 @deftypefn {C Macro} SCM SCM_SIMPLE_VECTOR_REF (SCM vec, size_t idx)
898 Evaluates to the element at position @var{idx} in the simple vector
899 @var{vec}. No type or range checking is done.
902 @deftypefn {C Macro} void SCM_SIMPLE_VECTOR_SET (SCM vec, size_t idx, SCM val)
903 Sets the element at position @var{idx} in the simple vector
904 @var{vec} to @var{val}. No type or range checking is done.
907 @deftypefn {C Function} {const SCM *} scm_vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
908 Acquire a handle for the vector @var{vec} and return a pointer to the
909 elements of it. This pointer can only be used to read the elements of
910 @var{vec}. When @var{vec} is not a vector, an error is signaled. The
911 handle mustr eventually be released with
912 @code{scm_array_handle_release}.
914 The variables pointed to by @var{lenp} and @var{incp} are filled with
915 the number of elements of the vector and the increment (number of
916 elements) between successive elements, respectively. Successive
917 elements of @var{vec} need not be contiguous in their underlying
918 ``root vector'' returned here; hence the increment is not necessarily
919 equal to 1 and may well be negative too (@pxref{Shared Arrays}).
921 The following example shows the typical way to use this function. It
922 creates a list of all elements of @var{vec} (in reverse order).
925 scm_t_array_handle handle;
931 elt = scm_vector_elements (vec, &handle, &len, &inc);
933 for (i = 0; i < len; i++, elt += inc)
934 list = scm_cons (*elt, list);
935 scm_array_handle_release (&handle);
940 @deftypefn {C Function} {SCM *} scm_vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
941 Like @code{scm_vector_elements} but the pointer can be used to modify
944 The following example shows the typical way to use this function. It
945 fills a vector with @code{#t}.
948 scm_t_array_handle handle;
953 elt = scm_vector_writable_elements (vec, &handle, &len, &inc);
954 for (i = 0; i < len; i++, elt += inc)
956 scm_array_handle_release (&handle);
961 @node Uniform Numeric Vectors
962 @subsection Uniform Numeric Vectors
964 A uniform numeric vector is a vector whose elements are all of a single
965 numeric type. Guile offers uniform numeric vectors for signed and
966 unsigned 8-bit, 16-bit, 32-bit, and 64-bit integers, two sizes of
967 floating point values, and complex floating-point numbers of these two
970 Strings could be regarded as uniform vectors of characters,
971 @xref{Strings}. Likewise, bit vectors could be regarded as uniform
972 vectors of bits, @xref{Bit Vectors}. Both are sufficiently different
973 from uniform numeric vectors that the procedures described here do not
974 apply to these two data types. However, both strings and bit vectors
975 are generalized vectors, @xref{Generalized Vectors}, and arrays,
978 Uniform numeric vectors are the special case of one dimensional uniform
981 Uniform numeric vectors can be useful since they consume less memory
982 than the non-uniform, general vectors. Also, since the types they can
983 store correspond directly to C types, it is easier to work with them
984 efficiently on a low level. Consider image processing as an example,
985 where you want to apply a filter to some image. While you could store
986 the pixels of an image in a general vector and write a general
987 convolution function, things are much more efficient with uniform
988 vectors: the convolution function knows that all pixels are unsigned
989 8-bit values (say), and can use a very tight inner loop.
991 That is, when it is written in C. Functions for efficiently working
992 with uniform numeric vectors from C are listed at the end of this
995 Procedures similar to the vector procedures (@pxref{Vectors}) are
996 provided for handling these uniform vectors, but they are distinct
997 datatypes and the two cannot be inter-mixed. If you want to work
998 primarily with uniform numeric vectors, but want to offer support for
999 general vectors as a convenience, you can use one of the
1000 @code{scm_any_to_*} functions. They will coerce lists and vectors to
1001 the given type of uniform vector. Alternatively, you can write two
1002 versions of your code: one that is fast and works only with uniform
1003 numeric vectors, and one that works with any kind of vector but is
1006 One set of the procedures listed below is a generic one: it works with
1007 all types of uniform numeric vectors. In addition to that, there is a
1008 set of procedures for each type that only works with that type. Unless
1009 you really need to the generality of the first set, it is best to use
1010 the more specific functions. They might not be that much faster, but
1011 their use can serve as a kind of declaration and makes it easier to
1014 The generic set of procedures uses @code{uniform} in its names, the
1015 specific ones use the tag from the following table.
1019 unsigned 8-bit integers
1022 signed 8-bit integers
1025 unsigned 16-bit integers
1028 signed 16-bit integers
1031 unsigned 32-bit integers
1034 signed 32-bit integers
1037 unsigned 64-bit integers
1040 signed 64-bit integers
1043 the C type @code{float}
1046 the C type @code{double}
1049 complex numbers in rectangular form with the real and imaginary part
1050 being a @code{float}
1053 complex numbers in rectangular form with the real and imaginary part
1054 being a @code{double}
1058 The external representation (ie.@: read syntax) for these vectors is
1059 similar to normal Scheme vectors, but with an additional tag from the
1060 table above indicating the vector's type. For example,
1067 Note that the read syntax for floating-point here conflicts with
1068 @code{#f} for false. In Standard Scheme one can write @code{(1 #f3)}
1069 for a three element list @code{(1 #f 3)}, but for Guile @code{(1 #f3)}
1070 is invalid. @code{(1 #f 3)} is almost certainly what one should write
1071 anyway to make the intention clear, so this is rarely a problem.
1073 @deffn {Scheme Procedure} uniform-vector? obj
1074 @deffnx {Scheme Procedure} u8vector? obj
1075 @deffnx {Scheme Procedure} s8vector? obj
1076 @deffnx {Scheme Procedure} u16vector? obj
1077 @deffnx {Scheme Procedure} s16vector? obj
1078 @deffnx {Scheme Procedure} u32vector? obj
1079 @deffnx {Scheme Procedure} s32vector? obj
1080 @deffnx {Scheme Procedure} u64vector? obj
1081 @deffnx {Scheme Procedure} s64vector? obj
1082 @deffnx {Scheme Procedure} f32vector? obj
1083 @deffnx {Scheme Procedure} f64vector? obj
1084 @deffnx {Scheme Procedure} c32vector? obj
1085 @deffnx {Scheme Procedure} c64vector? obj
1086 @deffnx {C Function} scm_uniform_vector_p (obj)
1087 @deffnx {C Function} scm_u8vector_p (obj)
1088 @deffnx {C Function} scm_s8vector_p (obj)
1089 @deffnx {C Function} scm_u16vector_p (obj)
1090 @deffnx {C Function} scm_s16vector_p (obj)
1091 @deffnx {C Function} scm_u32vector_p (obj)
1092 @deffnx {C Function} scm_s32vector_p (obj)
1093 @deffnx {C Function} scm_u64vector_p (obj)
1094 @deffnx {C Function} scm_s64vector_p (obj)
1095 @deffnx {C Function} scm_f32vector_p (obj)
1096 @deffnx {C Function} scm_f64vector_p (obj)
1097 @deffnx {C Function} scm_c32vector_p (obj)
1098 @deffnx {C Function} scm_c64vector_p (obj)
1099 Return @code{#t} if @var{obj} is a homogeneous numeric vector of the
1103 @deffn {Scheme Procedure} make-u8vector n [value]
1104 @deffnx {Scheme Procedure} make-s8vector n [value]
1105 @deffnx {Scheme Procedure} make-u16vector n [value]
1106 @deffnx {Scheme Procedure} make-s16vector n [value]
1107 @deffnx {Scheme Procedure} make-u32vector n [value]
1108 @deffnx {Scheme Procedure} make-s32vector n [value]
1109 @deffnx {Scheme Procedure} make-u64vector n [value]
1110 @deffnx {Scheme Procedure} make-s64vector n [value]
1111 @deffnx {Scheme Procedure} make-f32vector n [value]
1112 @deffnx {Scheme Procedure} make-f64vector n [value]
1113 @deffnx {Scheme Procedure} make-c32vector n [value]
1114 @deffnx {Scheme Procedure} make-c64vector n [value]
1115 @deffnx {C Function} scm_make_u8vector n [value]
1116 @deffnx {C Function} scm_make_s8vector n [value]
1117 @deffnx {C Function} scm_make_u16vector n [value]
1118 @deffnx {C Function} scm_make_s16vector n [value]
1119 @deffnx {C Function} scm_make_u32vector n [value]
1120 @deffnx {C Function} scm_make_s32vector n [value]
1121 @deffnx {C Function} scm_make_u64vector n [value]
1122 @deffnx {C Function} scm_make_s64vector n [value]
1123 @deffnx {C Function} scm_make_f32vector n [value]
1124 @deffnx {C Function} scm_make_f64vector n [value]
1125 @deffnx {C Function} scm_make_c32vector n [value]
1126 @deffnx {C Function} scm_make_c64vector n [value]
1127 Return a newly allocated homogeneous numeric vector holding @var{n}
1128 elements of the indicated type. If @var{value} is given, the vector
1129 is initialized with that value, otherwise the contents are
1133 @deffn {Scheme Procedure} u8vector value @dots{}
1134 @deffnx {Scheme Procedure} s8vector value @dots{}
1135 @deffnx {Scheme Procedure} u16vector value @dots{}
1136 @deffnx {Scheme Procedure} s16vector value @dots{}
1137 @deffnx {Scheme Procedure} u32vector value @dots{}
1138 @deffnx {Scheme Procedure} s32vector value @dots{}
1139 @deffnx {Scheme Procedure} u64vector value @dots{}
1140 @deffnx {Scheme Procedure} s64vector value @dots{}
1141 @deffnx {Scheme Procedure} f32vector value @dots{}
1142 @deffnx {Scheme Procedure} f64vector value @dots{}
1143 @deffnx {Scheme Procedure} c32vector value @dots{}
1144 @deffnx {Scheme Procedure} c64vector value @dots{}
1145 @deffnx {C Function} scm_u8vector (values)
1146 @deffnx {C Function} scm_s8vector (values)
1147 @deffnx {C Function} scm_u16vector (values)
1148 @deffnx {C Function} scm_s16vector (values)
1149 @deffnx {C Function} scm_u32vector (values)
1150 @deffnx {C Function} scm_s32vector (values)
1151 @deffnx {C Function} scm_u64vector (values)
1152 @deffnx {C Function} scm_s64vector (values)
1153 @deffnx {C Function} scm_f32vector (values)
1154 @deffnx {C Function} scm_f64vector (values)
1155 @deffnx {C Function} scm_c32vector (values)
1156 @deffnx {C Function} scm_c64vector (values)
1157 Return a newly allocated homogeneous numeric vector of the indicated
1158 type, holding the given parameter @var{value}s. The vector length is
1159 the number of parameters given.
1162 @deffn {Scheme Procedure} uniform-vector-length vec
1163 @deffnx {Scheme Procedure} u8vector-length vec
1164 @deffnx {Scheme Procedure} s8vector-length vec
1165 @deffnx {Scheme Procedure} u16vector-length vec
1166 @deffnx {Scheme Procedure} s16vector-length vec
1167 @deffnx {Scheme Procedure} u32vector-length vec
1168 @deffnx {Scheme Procedure} s32vector-length vec
1169 @deffnx {Scheme Procedure} u64vector-length vec
1170 @deffnx {Scheme Procedure} s64vector-length vec
1171 @deffnx {Scheme Procedure} f32vector-length vec
1172 @deffnx {Scheme Procedure} f64vector-length vec
1173 @deffnx {Scheme Procedure} c32vector-length vec
1174 @deffnx {Scheme Procedure} c64vector-length vec
1175 @deffnx {C Function} scm_uniform_vector_length (vec)
1176 @deffnx {C Function} scm_u8vector_length (vec)
1177 @deffnx {C Function} scm_s8vector_length (vec)
1178 @deffnx {C Function} scm_u16vector_length (vec)
1179 @deffnx {C Function} scm_s16vector_length (vec)
1180 @deffnx {C Function} scm_u32vector_length (vec)
1181 @deffnx {C Function} scm_s32vector_length (vec)
1182 @deffnx {C Function} scm_u64vector_length (vec)
1183 @deffnx {C Function} scm_s64vector_length (vec)
1184 @deffnx {C Function} scm_f32vector_length (vec)
1185 @deffnx {C Function} scm_f64vector_length (vec)
1186 @deffnx {C Function} scm_c32vector_length (vec)
1187 @deffnx {C Function} scm_c64vector_length (vec)
1188 Return the number of elements in @var{vec}.
1191 @deffn {Scheme Procedure} uniform-vector-ref vec i
1192 @deffnx {Scheme Procedure} u8vector-ref vec i
1193 @deffnx {Scheme Procedure} s8vector-ref vec i
1194 @deffnx {Scheme Procedure} u16vector-ref vec i
1195 @deffnx {Scheme Procedure} s16vector-ref vec i
1196 @deffnx {Scheme Procedure} u32vector-ref vec i
1197 @deffnx {Scheme Procedure} s32vector-ref vec i
1198 @deffnx {Scheme Procedure} u64vector-ref vec i
1199 @deffnx {Scheme Procedure} s64vector-ref vec i
1200 @deffnx {Scheme Procedure} f32vector-ref vec i
1201 @deffnx {Scheme Procedure} f64vector-ref vec i
1202 @deffnx {Scheme Procedure} c32vector-ref vec i
1203 @deffnx {Scheme Procedure} c64vector-ref vec i
1204 @deffnx {C Function} scm_uniform_vector_ref (vec i)
1205 @deffnx {C Function} scm_u8vector_ref (vec i)
1206 @deffnx {C Function} scm_s8vector_ref (vec i)
1207 @deffnx {C Function} scm_u16vector_ref (vec i)
1208 @deffnx {C Function} scm_s16vector_ref (vec i)
1209 @deffnx {C Function} scm_u32vector_ref (vec i)
1210 @deffnx {C Function} scm_s32vector_ref (vec i)
1211 @deffnx {C Function} scm_u64vector_ref (vec i)
1212 @deffnx {C Function} scm_s64vector_ref (vec i)
1213 @deffnx {C Function} scm_f32vector_ref (vec i)
1214 @deffnx {C Function} scm_f64vector_ref (vec i)
1215 @deffnx {C Function} scm_c32vector_ref (vec i)
1216 @deffnx {C Function} scm_c64vector_ref (vec i)
1217 Return the element at index @var{i} in @var{vec}. The first element
1218 in @var{vec} is index 0.
1221 @deffn {Scheme Procedure} uniform-vector-set! vec i value
1222 @deffnx {Scheme Procedure} u8vector-set! vec i value
1223 @deffnx {Scheme Procedure} s8vector-set! vec i value
1224 @deffnx {Scheme Procedure} u16vector-set! vec i value
1225 @deffnx {Scheme Procedure} s16vector-set! vec i value
1226 @deffnx {Scheme Procedure} u32vector-set! vec i value
1227 @deffnx {Scheme Procedure} s32vector-set! vec i value
1228 @deffnx {Scheme Procedure} u64vector-set! vec i value
1229 @deffnx {Scheme Procedure} s64vector-set! vec i value
1230 @deffnx {Scheme Procedure} f32vector-set! vec i value
1231 @deffnx {Scheme Procedure} f64vector-set! vec i value
1232 @deffnx {Scheme Procedure} c32vector-set! vec i value
1233 @deffnx {Scheme Procedure} c64vector-set! vec i value
1234 @deffnx {C Function} scm_uniform_vector_set_x (vec i value)
1235 @deffnx {C Function} scm_u8vector_set_x (vec i value)
1236 @deffnx {C Function} scm_s8vector_set_x (vec i value)
1237 @deffnx {C Function} scm_u16vector_set_x (vec i value)
1238 @deffnx {C Function} scm_s16vector_set_x (vec i value)
1239 @deffnx {C Function} scm_u32vector_set_x (vec i value)
1240 @deffnx {C Function} scm_s32vector_set_x (vec i value)
1241 @deffnx {C Function} scm_u64vector_set_x (vec i value)
1242 @deffnx {C Function} scm_s64vector_set_x (vec i value)
1243 @deffnx {C Function} scm_f32vector_set_x (vec i value)
1244 @deffnx {C Function} scm_f64vector_set_x (vec i value)
1245 @deffnx {C Function} scm_c32vector_set_x (vec i value)
1246 @deffnx {C Function} scm_c64vector_set_x (vec i value)
1247 Set the element at index @var{i} in @var{vec} to @var{value}. The
1248 first element in @var{vec} is index 0. The return value is
1252 @deffn {Scheme Procedure} uniform-vector->list vec
1253 @deffnx {Scheme Procedure} u8vector->list vec
1254 @deffnx {Scheme Procedure} s8vector->list vec
1255 @deffnx {Scheme Procedure} u16vector->list vec
1256 @deffnx {Scheme Procedure} s16vector->list vec
1257 @deffnx {Scheme Procedure} u32vector->list vec
1258 @deffnx {Scheme Procedure} s32vector->list vec
1259 @deffnx {Scheme Procedure} u64vector->list vec
1260 @deffnx {Scheme Procedure} s64vector->list vec
1261 @deffnx {Scheme Procedure} f32vector->list vec
1262 @deffnx {Scheme Procedure} f64vector->list vec
1263 @deffnx {Scheme Procedure} c32vector->list vec
1264 @deffnx {Scheme Procedure} c64vector->list vec
1265 @deffnx {C Function} scm_uniform_vector_to_list (vec)
1266 @deffnx {C Function} scm_u8vector_to_list (vec)
1267 @deffnx {C Function} scm_s8vector_to_list (vec)
1268 @deffnx {C Function} scm_u16vector_to_list (vec)
1269 @deffnx {C Function} scm_s16vector_to_list (vec)
1270 @deffnx {C Function} scm_u32vector_to_list (vec)
1271 @deffnx {C Function} scm_s32vector_to_list (vec)
1272 @deffnx {C Function} scm_u64vector_to_list (vec)
1273 @deffnx {C Function} scm_s64vector_to_list (vec)
1274 @deffnx {C Function} scm_f32vector_to_list (vec)
1275 @deffnx {C Function} scm_f64vector_to_list (vec)
1276 @deffnx {C Function} scm_c32vector_to_list (vec)
1277 @deffnx {C Function} scm_c64vector_to_list (vec)
1278 Return a newly allocated list holding all elements of @var{vec}.
1281 @deffn {Scheme Procedure} list->u8vector lst
1282 @deffnx {Scheme Procedure} list->s8vector lst
1283 @deffnx {Scheme Procedure} list->u16vector lst
1284 @deffnx {Scheme Procedure} list->s16vector lst
1285 @deffnx {Scheme Procedure} list->u32vector lst
1286 @deffnx {Scheme Procedure} list->s32vector lst
1287 @deffnx {Scheme Procedure} list->u64vector lst
1288 @deffnx {Scheme Procedure} list->s64vector lst
1289 @deffnx {Scheme Procedure} list->f32vector lst
1290 @deffnx {Scheme Procedure} list->f64vector lst
1291 @deffnx {Scheme Procedure} list->c32vector lst
1292 @deffnx {Scheme Procedure} list->c64vector lst
1293 @deffnx {C Function} scm_list_to_u8vector (lst)
1294 @deffnx {C Function} scm_list_to_s8vector (lst)
1295 @deffnx {C Function} scm_list_to_u16vector (lst)
1296 @deffnx {C Function} scm_list_to_s16vector (lst)
1297 @deffnx {C Function} scm_list_to_u32vector (lst)
1298 @deffnx {C Function} scm_list_to_s32vector (lst)
1299 @deffnx {C Function} scm_list_to_u64vector (lst)
1300 @deffnx {C Function} scm_list_to_s64vector (lst)
1301 @deffnx {C Function} scm_list_to_f32vector (lst)
1302 @deffnx {C Function} scm_list_to_f64vector (lst)
1303 @deffnx {C Function} scm_list_to_c32vector (lst)
1304 @deffnx {C Function} scm_list_to_c64vector (lst)
1305 Return a newly allocated homogeneous numeric vector of the indicated type,
1306 initialized with the elements of the list @var{lst}.
1309 @deffn {Scheme Procedure} any->u8vector obj
1310 @deffnx {Scheme Procedure} any->s8vector obj
1311 @deffnx {Scheme Procedure} any->u16vector obj
1312 @deffnx {Scheme Procedure} any->s16vector obj
1313 @deffnx {Scheme Procedure} any->u32vector obj
1314 @deffnx {Scheme Procedure} any->s32vector obj
1315 @deffnx {Scheme Procedure} any->u64vector obj
1316 @deffnx {Scheme Procedure} any->s64vector obj
1317 @deffnx {Scheme Procedure} any->f32vector obj
1318 @deffnx {Scheme Procedure} any->f64vector obj
1319 @deffnx {Scheme Procedure} any->c32vector obj
1320 @deffnx {Scheme Procedure} any->c64vector obj
1321 @deffnx {C Function} scm_any_to_u8vector (obj)
1322 @deffnx {C Function} scm_any_to_s8vector (obj)
1323 @deffnx {C Function} scm_any_to_u16vector (obj)
1324 @deffnx {C Function} scm_any_to_s16vector (obj)
1325 @deffnx {C Function} scm_any_to_u32vector (obj)
1326 @deffnx {C Function} scm_any_to_s32vector (obj)
1327 @deffnx {C Function} scm_any_to_u64vector (obj)
1328 @deffnx {C Function} scm_any_to_s64vector (obj)
1329 @deffnx {C Function} scm_any_to_f32vector (obj)
1330 @deffnx {C Function} scm_any_to_f64vector (obj)
1331 @deffnx {C Function} scm_any_to_c32vector (obj)
1332 @deffnx {C Function} scm_any_to_c64vector (obj)
1333 Return a (maybe newly allocated) uniform numeric vector of the indicated
1334 type, initialized with the elements of @var{obj}, which must be a list,
1335 a vector, or a uniform vector. When @var{obj} is already a suitable
1336 uniform numeric vector, it is returned unchanged.
1339 @deftypefn {C Function} int scm_is_uniform_vector (SCM uvec)
1340 Return non-zero when @var{uvec} is a uniform numeric vector, zero
1344 @deftypefn {C Function} SCM scm_take_u8vector (const scm_t_uint8 *data, size_t len)
1345 @deftypefnx {C Function} SCM scm_take_s8vector (const scm_t_int8 *data, size_t len)
1346 @deftypefnx {C Function} SCM scm_take_u16vector (const scm_t_uint16 *data, size_t len)
1347 @deftypefnx {C Function} SCM scm_take_s16vector (const scm_t_int16 *data, size_t len)
1348 @deftypefnx {C Function} SCM scm_take_u32vector (const scm_t_uint32 *data, size_t len)
1349 @deftypefnx {C Function} SCM scm_take_s32vector (const scm_t_int32 *data, size_t len)
1350 @deftypefnx {C Function} SCM scm_take_u64vector (const scm_t_uint64 *data, size_t len)
1351 @deftypefnx {C Function} SCM scm_take_s64vector (const scm_t_int64 *data, size_t len)
1352 @deftypefnx {C Function} SCM scm_take_f32vector (const float *data, size_t len)
1353 @deftypefnx {C Function} SCM scm_take_f64vector (const double *data, size_t len)
1354 @deftypefnx {C Function} SCM scm_take_c32vector (const float *data, size_t len)
1355 @deftypefnx {C Function} SCM scm_take_c64vector (const double *data, size_t len)
1356 Return a new uniform numeric vector of the indicated type and length
1357 that uses the memory pointed to by @var{data} to store its elements.
1358 This memory will eventually be freed with @code{free}. The argument
1359 @var{len} specifies the number of elements in @var{data}, not its size
1362 The @code{c32} and @code{c64} variants take a pointer to a C array of
1363 @code{float}s or @code{double}s. The real parts of the complex numbers
1364 are at even indices in that array, the corresponding imaginary parts are
1365 at the following odd index.
1368 @deftypefn {C Function} size_t scm_c_uniform_vector_length (SCM uvec)
1369 Return the number of elements of @var{uvec} as a @code{size_t}.
1372 @deftypefn {C Function} {const void *} scm_uniform_vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1373 @deftypefnx {C Function} {const scm_t_uint8 *} scm_u8vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1374 @deftypefnx {C Function} {const scm_t_int8 *} scm_s8vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1375 @deftypefnx {C Function} {const scm_t_uint16 *} scm_u16vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1376 @deftypefnx {C Function} {const scm_t_int16 *} scm_s16vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1377 @deftypefnx {C Function} {const scm_t_uint32 *} scm_u32vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1378 @deftypefnx {C Function} {const scm_t_int32 *} scm_s32vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1379 @deftypefnx {C Function} {const scm_t_uint64 *} scm_u64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1380 @deftypefnx {C Function} {const scm_t_int64 *} scm_s64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1381 @deftypefnx {C Function} {const float *} scm_f23vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1382 @deftypefnx {C Function} {const double *} scm_f64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1383 @deftypefnx {C Function} {const float *} scm_c32vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1384 @deftypefnx {C Function} {const double *} scm_c64vector_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1385 Like @code{scm_vector_elements} (@pxref{Vector Accessing from C}), but
1386 returns a pointer to the elements of a uniform numeric vector of the
1390 @deftypefn {C Function} {void *} scm_uniform_vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1391 @deftypefnx {C Function} {scm_t_uint8 *} scm_u8vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1392 @deftypefnx {C Function} {scm_t_int8 *} scm_s8vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1393 @deftypefnx {C Function} {scm_t_uint16 *} scm_u16vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1394 @deftypefnx {C Function} {scm_t_int16 *} scm_s16vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1395 @deftypefnx {C Function} {scm_t_uint32 *} scm_u32vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1396 @deftypefnx {C Function} {scm_t_int32 *} scm_s32vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1397 @deftypefnx {C Function} {scm_t_uint64 *} scm_u64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1398 @deftypefnx {C Function} {scm_t_int64 *} scm_s64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1399 @deftypefnx {C Function} {float *} scm_f23vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1400 @deftypefnx {C Function} {double *} scm_f64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1401 @deftypefnx {C Function} {float *} scm_c32vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1402 @deftypefnx {C Function} {double *} scm_c64vector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *lenp, ssize_t *incp)
1403 Like @code{scm_vector_writable_elements} (@pxref{Vector Accessing from
1404 C}), but returns a pointer to the elements of a uniform numeric vector
1405 of the indicated kind.
1408 Uniform numeric vectors can be written to and read from input/output
1409 ports using the procedures listed below. However, bytevectors may often
1410 be more convenient for binary input/output since they provide more
1411 flexibility in the interpretation of raw byte sequences
1412 (@pxref{Bytevectors}).
1414 @deffn {Scheme Procedure} uniform-vector-read! uvec [port_or_fd [start [end]]]
1415 @deffnx {C Function} scm_uniform_vector_read_x (uvec, port_or_fd, start, end)
1416 Fill the elements of @var{uvec} by reading
1417 raw bytes from @var{port-or-fdes}, using host byte order.
1419 The optional arguments @var{start} (inclusive) and @var{end}
1420 (exclusive) allow a specified region to be read,
1421 leaving the remainder of the vector unchanged.
1423 When @var{port-or-fdes} is a port, all specified elements
1424 of @var{uvec} are attempted to be read, potentially blocking
1425 while waiting formore input or end-of-file.
1426 When @var{port-or-fd} is an integer, a single call to
1429 An error is signalled when the last element has only
1430 been partially filled before reaching end-of-file or in
1431 the single call to read(2).
1433 @code{uniform-vector-read!} returns the number of elements
1436 @var{port-or-fdes} may be omitted, in which case it defaults
1437 to the value returned by @code{(current-input-port)}.
1440 @deffn {Scheme Procedure} uniform-vector-write uvec [port_or_fd [start [end]]]
1441 @deffnx {C Function} scm_uniform_vector_write (uvec, port_or_fd, start, end)
1442 Write the elements of @var{uvec} as raw bytes to
1443 @var{port-or-fdes}, in the host byte order.
1445 The optional arguments @var{start} (inclusive)
1446 and @var{end} (exclusive) allow
1447 a specified region to be written.
1449 When @var{port-or-fdes} is a port, all specified elements
1450 of @var{uvec} are attempted to be written, potentially blocking
1451 while waiting for more room.
1452 When @var{port-or-fd} is an integer, a single call to
1455 An error is signalled when the last element has only
1456 been partially written in the single call to write(2).
1458 The number of objects actually written is returned.
1459 @var{port-or-fdes} may be
1460 omitted, in which case it defaults to the value returned by
1461 @code{(current-output-port)}.
1466 @subsection Bit Vectors
1469 Bit vectors are zero-origin, one-dimensional arrays of booleans. They
1470 are displayed as a sequence of @code{0}s and @code{1}s prefixed by
1474 (make-bitvector 8 #f) @result{}
1478 Bit vectors are also generalized vectors, @xref{Generalized
1479 Vectors}, and can thus be used with the array procedures, @xref{Arrays}.
1480 Bit vectors are the special case of one dimensional bit arrays.
1482 @deffn {Scheme Procedure} bitvector? obj
1483 @deffnx {C Function} scm_bitvector_p (obj)
1484 Return @code{#t} when @var{obj} is a bitvector, else
1488 @deftypefn {C Function} int scm_is_bitvector (SCM obj)
1489 Return @code{1} when @var{obj} is a bitvector, else return @code{0}.
1492 @deffn {Scheme Procedure} make-bitvector len [fill]
1493 @deffnx {C Function} scm_make_bitvector (len, fill)
1494 Create a new bitvector of length @var{len} and
1495 optionally initialize all elements to @var{fill}.
1498 @deftypefn {C Function} SCM scm_c_make_bitvector (size_t len, SCM fill)
1499 Like @code{scm_make_bitvector}, but the length is given as a
1503 @deffn {Scheme Procedure} bitvector . bits
1504 @deffnx {C Function} scm_bitvector (bits)
1505 Create a new bitvector with the arguments as elements.
1508 @deffn {Scheme Procedure} bitvector-length vec
1509 @deffnx {C Function} scm_bitvector_length (vec)
1510 Return the length of the bitvector @var{vec}.
1513 @deftypefn {C Function} size_t scm_c_bitvector_length (SCM vec)
1514 Like @code{scm_bitvector_length}, but the length is returned as a
1518 @deffn {Scheme Procedure} bitvector-ref vec idx
1519 @deffnx {C Function} scm_bitvector_ref (vec, idx)
1520 Return the element at index @var{idx} of the bitvector
1524 @deftypefn {C Function} SCM scm_c_bitvector_ref (SCM obj, size_t idx)
1525 Return the element at index @var{idx} of the bitvector
1529 @deffn {Scheme Procedure} bitvector-set! vec idx val
1530 @deffnx {C Function} scm_bitvector_set_x (vec, idx, val)
1531 Set the element at index @var{idx} of the bitvector
1532 @var{vec} when @var{val} is true, else clear it.
1535 @deftypefn {C Function} SCM scm_c_bitvector_set_x (SCM obj, size_t idx, SCM val)
1536 Set the element at index @var{idx} of the bitvector
1537 @var{vec} when @var{val} is true, else clear it.
1540 @deffn {Scheme Procedure} bitvector-fill! vec val
1541 @deffnx {C Function} scm_bitvector_fill_x (vec, val)
1542 Set all elements of the bitvector
1543 @var{vec} when @var{val} is true, else clear them.
1546 @deffn {Scheme Procedure} list->bitvector list
1547 @deffnx {C Function} scm_list_to_bitvector (list)
1548 Return a new bitvector initialized with the elements
1552 @deffn {Scheme Procedure} bitvector->list vec
1553 @deffnx {C Function} scm_bitvector_to_list (vec)
1554 Return a new list initialized with the elements
1555 of the bitvector @var{vec}.
1558 @deffn {Scheme Procedure} bit-count bool bitvector
1559 @deffnx {C Function} scm_bit_count (bool, bitvector)
1560 Return a count of how many entries in @var{bitvector} are equal to
1561 @var{bool}. For example,
1564 (bit-count #f #*000111000) @result{} 6
1568 @deffn {Scheme Procedure} bit-position bool bitvector start
1569 @deffnx {C Function} scm_bit_position (bool, bitvector, start)
1570 Return the index of the first occurrence of @var{bool} in
1571 @var{bitvector}, starting from @var{start}. If there is no @var{bool}
1572 entry between @var{start} and the end of @var{bitvector}, then return
1573 @code{#f}. For example,
1576 (bit-position #t #*000101 0) @result{} 3
1577 (bit-position #f #*0001111 3) @result{} #f
1581 @deffn {Scheme Procedure} bit-invert! bitvector
1582 @deffnx {C Function} scm_bit_invert_x (bitvector)
1583 Modify @var{bitvector} by replacing each element with its negation.
1586 @deffn {Scheme Procedure} bit-set*! bitvector uvec bool
1587 @deffnx {C Function} scm_bit_set_star_x (bitvector, uvec, bool)
1588 Set entries of @var{bitvector} to @var{bool}, with @var{uvec}
1589 selecting the entries to change. The return value is unspecified.
1591 If @var{uvec} is a bit vector, then those entries where it has
1592 @code{#t} are the ones in @var{bitvector} which are set to @var{bool}.
1593 @var{uvec} and @var{bitvector} must be the same length. When
1594 @var{bool} is @code{#t} it's like @var{uvec} is OR'ed into
1595 @var{bitvector}. Or when @var{bool} is @code{#f} it can be seen as an
1599 (define bv #*01000010)
1600 (bit-set*! bv #*10010001 #t)
1602 @result{} #*11010011
1605 If @var{uvec} is a uniform vector of unsigned long integers, then
1606 they're indexes into @var{bitvector} which are set to @var{bool}.
1609 (define bv #*01000010)
1610 (bit-set*! bv #u(5 2 7) #t)
1612 @result{} #*01100111
1616 @deffn {Scheme Procedure} bit-count* bitvector uvec bool
1617 @deffnx {C Function} scm_bit_count_star (bitvector, uvec, bool)
1618 Return a count of how many entries in @var{bitvector} are equal to
1619 @var{bool}, with @var{uvec} selecting the entries to consider.
1621 @var{uvec} is interpreted in the same way as for @code{bit-set*!}
1622 above. Namely, if @var{uvec} is a bit vector then entries which have
1623 @code{#t} there are considered in @var{bitvector}. Or if @var{uvec}
1624 is a uniform vector of unsigned long integers then it's the indexes in
1625 @var{bitvector} to consider.
1630 (bit-count* #*01110111 #*11001101 #t) @result{} 3
1631 (bit-count* #*01110111 #u(7 0 4) #f) @result{} 2
1635 @deftypefn {C Function} {const scm_t_uint32 *} scm_bitvector_elements (SCM vec, scm_t_array_handle *handle, size_t *offp, size_t *lenp, ssize_t *incp)
1636 Like @code{scm_vector_elements} (@pxref{Vector Accessing from C}), but
1637 for bitvectors. The variable pointed to by @var{offp} is set to the
1638 value returned by @code{scm_array_handle_bit_elements_offset}. See
1639 @code{scm_array_handle_bit_elements} for how to use the returned
1640 pointer and the offset.
1643 @deftypefn {C Function} {scm_t_uint32 *} scm_bitvector_writable_elements (SCM vec, scm_t_array_handle *handle, size_t *offp, size_t *lenp, ssize_t *incp)
1644 Like @code{scm_bitvector_elements}, but the pointer is good for reading
1648 @node Generalized Vectors
1649 @subsection Generalized Vectors
1651 Guile has a number of data types that are generally vector-like:
1652 strings, uniform numeric vectors, bytevectors, bitvectors, and of course
1653 ordinary vectors of arbitrary Scheme values. These types are disjoint:
1654 a Scheme value belongs to at most one of the five types listed above.
1656 If you want to gloss over this distinction and want to treat all four
1657 types with common code, you can use the procedures in this section.
1658 They work with the @emph{generalized vector} type, which is the union
1659 of the five vector-like types.
1661 @deffn {Scheme Procedure} generalized-vector? obj
1662 @deffnx {C Function} scm_generalized_vector_p (obj)
1663 Return @code{#t} if @var{obj} is a vector, bytevector, string,
1664 bitvector, or uniform numeric vector.
1667 @deffn {Scheme Procedure} generalized-vector-length v
1668 @deffnx {C Function} scm_generalized_vector_length (v)
1669 Return the length of the generalized vector @var{v}.
1672 @deffn {Scheme Procedure} generalized-vector-ref v idx
1673 @deffnx {C Function} scm_generalized_vector_ref (v, idx)
1674 Return the element at index @var{idx} of the
1675 generalized vector @var{v}.
1678 @deffn {Scheme Procedure} generalized-vector-set! v idx val
1679 @deffnx {C Function} scm_generalized_vector_set_x (v, idx, val)
1680 Set the element at index @var{idx} of the
1681 generalized vector @var{v} to @var{val}.
1684 @deffn {Scheme Procedure} generalized-vector->list v
1685 @deffnx {C Function} scm_generalized_vector_to_list (v)
1686 Return a new list whose elements are the elements of the
1687 generalized vector @var{v}.
1690 @deftypefn {C Function} int scm_is_generalized_vector (SCM obj)
1691 Return @code{1} if @var{obj} is a vector, string,
1692 bitvector, or uniform numeric vector; else return @code{0}.
1695 @deftypefn {C Function} size_t scm_c_generalized_vector_length (SCM v)
1696 Return the length of the generalized vector @var{v}.
1699 @deftypefn {C Function} SCM scm_c_generalized_vector_ref (SCM v, size_t idx)
1700 Return the element at index @var{idx} of the generalized vector @var{v}.
1703 @deftypefn {C Function} void scm_c_generalized_vector_set_x (SCM v, size_t idx, SCM val)
1704 Set the element at index @var{idx} of the generalized vector @var{v}
1708 @deftypefn {C Function} void scm_generalized_vector_get_handle (SCM v, scm_t_array_handle *handle)
1709 Like @code{scm_array_get_handle} but an error is signalled when @var{v}
1710 is not of rank one. You can use @code{scm_array_handle_ref} and
1711 @code{scm_array_handle_set} to read and write the elements of @var{v},
1712 or you can use functions like @code{scm_array_handle_<foo>_elements} to
1713 deal with specific types of vectors.
1720 @dfn{Arrays} are a collection of cells organized into an arbitrary
1721 number of dimensions. Each cell can be accessed in constant time by
1722 supplying an index for each dimension.
1724 In the current implementation, an array uses a generalized vector for
1725 the actual storage of its elements. Any kind of generalized vector
1726 will do, so you can have arrays of uniform numeric values, arrays of
1727 characters, arrays of bits, and of course, arrays of arbitrary Scheme
1728 values. For example, arrays with an underlying @code{c64vector} might
1729 be nice for digital signal processing, while arrays made from a
1730 @code{u8vector} might be used to hold gray-scale images.
1732 The number of dimensions of an array is called its @dfn{rank}. Thus,
1733 a matrix is an array of rank 2, while a vector has rank 1. When
1734 accessing an array element, you have to specify one exact integer for
1735 each dimension. These integers are called the @dfn{indices} of the
1736 element. An array specifies the allowed range of indices for each
1737 dimension via an inclusive lower and upper bound. These bounds can
1738 well be negative, but the upper bound must be greater than or equal to
1739 the lower bound minus one. When all lower bounds of an array are
1740 zero, it is called a @dfn{zero-origin} array.
1742 Arrays can be of rank 0, which could be interpreted as a scalar.
1743 Thus, a zero-rank array can store exactly one object and the list of
1744 indices of this element is the empty list.
1746 Arrays contain zero elements when one of their dimensions has a zero
1747 length. These empty arrays maintain information about their shape: a
1748 matrix with zero columns and 3 rows is different from a matrix with 3
1749 columns and zero rows, which again is different from a vector of
1752 Generalized vectors, such as strings, uniform numeric vectors,
1753 bytevectors, bit vectors and ordinary vectors, are the special case of
1754 one dimensional arrays.
1758 * Array Procedures::
1760 * Accessing Arrays from C::
1764 @subsubsection Array Syntax
1766 An array is displayed as @code{#} followed by its rank, followed by a
1767 tag that describes the underlying vector, optionally followed by
1768 information about its shape, and finally followed by the cells,
1769 organized into dimensions using parentheses.
1771 In more words, the array tag is of the form
1774 #<rank><vectag><@@lower><:len><@@lower><:len>...
1777 where @code{<rank>} is a positive integer in decimal giving the rank of
1778 the array. It is omitted when the rank is 1 and the array is non-shared
1779 and has zero-origin (see below). For shared arrays and for a non-zero
1780 origin, the rank is always printed even when it is 1 to distinguish
1781 them from ordinary vectors.
1783 The @code{<vectag>} part is the tag for a uniform numeric vector, like
1784 @code{u8}, @code{s16}, etc, @code{b} for bitvectors, or @code{a} for
1785 strings. It is empty for ordinary vectors.
1787 The @code{<@@lower>} part is a @samp{@@} character followed by a signed
1788 integer in decimal giving the lower bound of a dimension. There is one
1789 @code{<@@lower>} for each dimension. When all lower bounds are zero,
1790 all @code{<@@lower>} parts are omitted.
1792 The @code{<:len>} part is a @samp{:} character followed by an unsigned
1793 integer in decimal giving the length of a dimension. Like for the lower
1794 bounds, there is one @code{<:len>} for each dimension, and the
1795 @code{<:len>} part always follows the @code{<@@lower>} part for a
1796 dimension. Lengths are only then printed when they can't be deduced
1797 from the nested lists of elements of the array literal, which can happen
1798 when at least one length is zero.
1800 As a special case, an array of rank 0 is printed as
1801 @code{#0<vectag>(<scalar>)}, where @code{<scalar>} is the result of
1802 printing the single element of the array.
1808 is an ordinary array of rank 1 with lower bound 0 in dimension 0.
1809 (I.e., a regular vector.)
1812 is an ordinary array of rank 1 with lower bound 2 in dimension 0.
1814 @item #2((1 2 3) (4 5 6))
1815 is a non-uniform array of rank 2; a 3@cross{}3 matrix with index ranges 0..2
1819 is a uniform u8 array of rank 1.
1821 @item #2u32@@2@@3((1 2) (2 3))
1822 is a uniform u8 array of rank 2 with index ranges 2..3 and 3..4.
1825 is a two-dimensional array with index ranges 0..-1 and 0..-1, i.e. both
1826 dimensions have length zero.
1829 is a two-dimensional array with index ranges 0..-1 and 0..1, i.e. the
1830 first dimension has length zero, but the second has length 2.
1833 is a rank-zero array with contents 12.
1837 In addition, bytevectors are also arrays, but use a different syntax
1838 (@pxref{Bytevectors}):
1843 is a 3-byte long bytevector, with contents 1, 2, 3.
1847 @node Array Procedures
1848 @subsubsection Array Procedures
1850 When an array is created, the range of each dimension must be
1851 specified, e.g., to create a 2@cross{}3 array with a zero-based index:
1854 (make-array 'ho 2 3) @result{} #2((ho ho ho) (ho ho ho))
1857 The range of each dimension can also be given explicitly, e.g., another
1858 way to create the same array:
1861 (make-array 'ho '(0 1) '(0 2)) @result{} #2((ho ho ho) (ho ho ho))
1864 The following procedures can be used with arrays (or vectors). An
1865 argument shown as @var{idx}@dots{} means one parameter for each
1866 dimension in the array. A @var{idxlist} argument means a list of such
1867 values, one for each dimension.
1870 @deffn {Scheme Procedure} array? obj
1871 @deffnx {C Function} scm_array_p (obj, unused)
1872 Return @code{#t} if the @var{obj} is an array, and @code{#f} if
1875 The second argument to scm_array_p is there for historical reasons,
1876 but it is not used. You should always pass @code{SCM_UNDEFINED} as
1880 @deffn {Scheme Procedure} typed-array? obj type
1881 @deffnx {C Function} scm_typed_array_p (obj, type)
1882 Return @code{#t} if the @var{obj} is an array of type @var{type}, and
1886 @deftypefn {C Function} int scm_is_array (SCM obj)
1887 Return @code{1} if the @var{obj} is an array and @code{0} if not.
1890 @deftypefn {C Function} int scm_is_typed_array (SCM obj, SCM type)
1891 Return @code{0} if the @var{obj} is an array of type @var{type}, and
1895 @deffn {Scheme Procedure} make-array fill bound @dots{}
1896 @deffnx {C Function} scm_make_array (fill, bounds)
1897 Equivalent to @code{(make-typed-array #t @var{fill} @var{bound} ...)}.
1900 @deffn {Scheme Procedure} make-typed-array type fill bound @dots{}
1901 @deffnx {C Function} scm_make_typed_array (type, fill, bounds)
1902 Create and return an array that has as many dimensions as there are
1903 @var{bound}s and (maybe) fill it with @var{fill}.
1905 The underlying storage vector is created according to @var{type},
1906 which must be a symbol whose name is the `vectag' of the array as
1907 explained above, or @code{#t} for ordinary, non-specialized arrays.
1909 For example, using the symbol @code{f64} for @var{type} will create an
1910 array that uses a @code{f64vector} for storing its elements, and
1911 @code{a} will use a string.
1913 When @var{fill} is not the special @emph{unspecified} value, the new
1914 array is filled with @var{fill}. Otherwise, the initial contents of
1915 the array is unspecified. The special @emph{unspecified} value is
1916 stored in the variable @code{*unspecified*} so that for example
1917 @code{(make-typed-array 'u32 *unspecified* 4)} creates a uninitialized
1918 @code{u32} vector of length 4.
1920 Each @var{bound} may be a positive non-zero integer @var{N}, in which
1921 case the index for that dimension can range from 0 through @var{N-1}; or
1922 an explicit index range specifier in the form @code{(LOWER UPPER)},
1923 where both @var{lower} and @var{upper} are integers, possibly less than
1924 zero, and possibly the same number (however, @var{lower} cannot be
1925 greater than @var{upper}).
1928 @deffn {Scheme Procedure} list->array dimspec list
1929 Equivalent to @code{(list->typed-array #t @var{dimspec}
1933 @deffn {Scheme Procedure} list->typed-array type dimspec list
1934 @deffnx {C Function} scm_list_to_typed_array (type, dimspec, list)
1935 Return an array of the type indicated by @var{type} with elements the
1936 same as those of @var{list}.
1938 The argument @var{dimspec} determines the number of dimensions of the
1939 array and their lower bounds. When @var{dimspec} is an exact integer,
1940 it gives the number of dimensions directly and all lower bounds are
1941 zero. When it is a list of exact integers, then each element is the
1942 lower index bound of a dimension, and there will be as many dimensions
1943 as elements in the list.
1946 @deffn {Scheme Procedure} array-type array
1947 Return the type of @var{array}. This is the `vectag' used for
1948 printing @var{array} (or @code{#t} for ordinary arrays) and can be
1949 used with @code{make-typed-array} to create an array of the same kind
1953 @deffn {Scheme Procedure} array-ref array idx @dots{}
1954 Return the element at @code{(idx @dots{})} in @var{array}.
1957 (define a (make-array 999 '(1 2) '(3 4)))
1958 (array-ref a 2 4) @result{} 999
1962 @deffn {Scheme Procedure} array-in-bounds? array idx @dots{}
1963 @deffnx {C Function} scm_array_in_bounds_p (array, idxlist)
1964 Return @code{#t} if the given index would be acceptable to
1968 (define a (make-array #f '(1 2) '(3 4)))
1969 (array-in-bounds? a 2 3) @result{} #t
1970 (array-in-bounds? a 0 0) @result{} #f
1974 @deffn {Scheme Procedure} array-set! array obj idx @dots{}
1975 @deffnx {C Function} scm_array_set_x (array, obj, idxlist)
1976 Set the element at @code{(idx @dots{})} in @var{array} to @var{obj}.
1977 The return value is unspecified.
1980 (define a (make-array #f '(0 1) '(0 1)))
1981 (array-set! a #t 1 1)
1982 a @result{} #2((#f #f) (#f #t))
1986 @deffn {Scheme Procedure} enclose-array array dim1 @dots{}
1987 @deffnx {C Function} scm_enclose_array (array, dimlist)
1988 @var{dim1}, @var{dim2} @dots{} should be nonnegative integers less than
1989 the rank of @var{array}. @code{enclose-array} returns an array
1990 resembling an array of shared arrays. The dimensions of each shared
1991 array are the same as the @var{dim}th dimensions of the original array,
1992 the dimensions of the outer array are the same as those of the original
1993 array that did not match a @var{dim}.
1995 An enclosed array is not a general Scheme array. Its elements may not
1996 be set using @code{array-set!}. Two references to the same element of
1997 an enclosed array will be @code{equal?} but will not in general be
1998 @code{eq?}. The value returned by @code{array-prototype} when given an
1999 enclosed array is unspecified.
2004 (enclose-array '#3(((a b c)
2010 #<enclosed-array (#1(a d) #1(b e) #1(c f))
2011 (#1(1 4) #1(2 5) #1(3 6))>
2013 (enclose-array '#3(((a b c)
2019 #<enclosed-array #2((a 1) (d 4))
2025 @deffn {Scheme Procedure} array-shape array
2026 @deffnx {Scheme Procedure} array-dimensions array
2027 @deffnx {C Function} scm_array_dimensions (array)
2028 Return a list of the bounds for each dimension of @var{array}.
2030 @code{array-shape} gives @code{(@var{lower} @var{upper})} for each
2031 dimension. @code{array-dimensions} instead returns just
2032 @math{@var{upper}+1} for dimensions with a 0 lower bound. Both are
2033 suitable as input to @code{make-array}.
2038 (define a (make-array 'foo '(-1 3) 5))
2039 (array-shape a) @result{} ((-1 3) (0 4))
2040 (array-dimensions a) @result{} ((-1 3) 5)
2044 @deffn {Scheme Procedure} array-rank obj
2045 @deffnx {C Function} scm_array_rank (obj)
2046 Return the rank of @var{array}.
2049 @deftypefn {C Function} size_t scm_c_array_rank (SCM array)
2050 Return the rank of @var{array} as a @code{size_t}.
2053 @deffn {Scheme Procedure} array->list array
2054 @deffnx {C Function} scm_array_to_list (array)
2055 Return a list consisting of all the elements, in order, of
2059 @c FIXME: Describe how the order affects the copying (it matters for
2060 @c shared arrays with the same underlying root vector, presumably).
2062 @deffn {Scheme Procedure} array-copy! src dst
2063 @deffnx {Scheme Procedure} array-copy-in-order! src dst
2064 @deffnx {C Function} scm_array_copy_x (src, dst)
2065 Copy every element from vector or array @var{src} to the corresponding
2066 element of @var{dst}. @var{dst} must have the same rank as @var{src},
2067 and be at least as large in each dimension. The return value is
2071 @deffn {Scheme Procedure} array-fill! array fill
2072 @deffnx {C Function} scm_array_fill_x (array, fill)
2073 Store @var{fill} in every element of @var{array}. The value returned
2077 @c begin (texi-doc-string "guile" "array-equal?")
2078 @deffn {Scheme Procedure} array-equal? array1 array2 @dots{}
2079 Return @code{#t} if all arguments are arrays with the same shape, the
2080 same type, and have corresponding elements which are either
2081 @code{equal?} or @code{array-equal?}. This function differs from
2082 @code{equal?} (@pxref{Equality}) in that a one dimensional shared
2083 array may be @code{array-equal?} but not @code{equal?} to a vector or
2087 @c FIXME: array-map! accepts no source arrays at all, and in that
2088 @c case makes calls "(proc)". Is that meant to be a documented
2091 @c FIXME: array-for-each doesn't say what happens if the sources have
2092 @c different index ranges. The code currently iterates over the
2093 @c indices of the first and expects the others to cover those. That
2094 @c at least vaguely matches array-map!, but is is meant to be a
2095 @c documented feature?
2097 @deffn {Scheme Procedure} array-map! dst proc src1 @dots{} srcN
2098 @deffnx {Scheme Procedure} array-map-in-order! dst proc src1 @dots{} srcN
2099 @deffnx {C Function} scm_array_map_x (dst, proc, srclist)
2100 Set each element of the @var{dst} array to values obtained from calls
2101 to @var{proc}. The value returned is unspecified.
2103 Each call is @code{(@var{proc} @var{elem1} @dots{} @var{elemN})},
2104 where each @var{elem} is from the corresponding @var{src} array, at
2105 the @var{dst} index. @code{array-map-in-order!} makes the calls in
2106 row-major order, @code{array-map!} makes them in an unspecified order.
2108 The @var{src} arrays must have the same number of dimensions as
2109 @var{dst}, and must have a range for each dimension which covers the
2110 range in @var{dst}. This ensures all @var{dst} indices are valid in
2114 @deffn {Scheme Procedure} array-for-each proc src1 @dots{} srcN
2115 @deffnx {C Function} scm_array_for_each (proc, src1, srclist)
2116 Apply @var{proc} to each tuple of elements of @var{src1} @dots{}
2117 @var{srcN}, in row-major order. The value returned is unspecified.
2120 @deffn {Scheme Procedure} array-index-map! dst proc
2121 @deffnx {C Function} scm_array_index_map_x (dst, proc)
2122 Set each element of the @var{dst} array to values returned by calls to
2123 @var{proc}. The value returned is unspecified.
2125 Each call is @code{(@var{proc} @var{i1} @dots{} @var{iN})}, where
2126 @var{i1}@dots{}@var{iN} is the destination index, one parameter for
2127 each dimension. The order in which the calls are made is unspecified.
2129 For example, to create a @m{4\times4, 4x4} matrix representing a
2133 \advance\leftskip by 2\lispnarrowing {
2151 (define a (make-array #f 4 4))
2152 (array-index-map! a (lambda (i j)
2153 (modulo (+ i j) 4)))
2157 @deffn {Scheme Procedure} uniform-array-read! ra [port_or_fd [start [end]]]
2158 @deffnx {C Function} scm_uniform_array_read_x (ra, port_or_fd, start, end)
2159 Attempt to read all elements of @var{ura}, in lexicographic order, as
2160 binary objects from @var{port-or-fdes}.
2161 If an end of file is encountered,
2162 the objects up to that point are put into @var{ura}
2163 (starting at the beginning) and the remainder of the array is
2166 The optional arguments @var{start} and @var{end} allow
2167 a specified region of a vector (or linearized array) to be read,
2168 leaving the remainder of the vector unchanged.
2170 @code{uniform-array-read!} returns the number of objects read.
2171 @var{port-or-fdes} may be omitted, in which case it defaults to the value
2172 returned by @code{(current-input-port)}.
2175 @deffn {Scheme Procedure} uniform-array-write v [port_or_fd [start [end]]]
2176 @deffnx {C Function} scm_uniform_array_write (v, port_or_fd, start, end)
2177 Writes all elements of @var{ura} as binary objects to
2180 The optional arguments @var{start}
2182 a specified region of a vector (or linearized array) to be written.
2184 The number of objects actually written is returned.
2185 @var{port-or-fdes} may be
2186 omitted, in which case it defaults to the value returned by
2187 @code{(current-output-port)}.
2191 @subsubsection Shared Arrays
2193 @deffn {Scheme Procedure} make-shared-array oldarray mapfunc bound @dots{}
2194 @deffnx {C Function} scm_make_shared_array (oldarray, mapfunc, boundlist)
2195 Return a new array which shares the storage of @var{oldarray}.
2196 Changes made through either affect the same underlying storage. The
2197 @var{bound@dots{}} arguments are the shape of the new array, the same
2198 as @code{make-array} (@pxref{Array Procedures}).
2200 @var{mapfunc} translates coordinates from the new array to the
2201 @var{oldarray}. It's called as @code{(@var{mapfunc} newidx1 @dots{})}
2202 with one parameter for each dimension of the new array, and should
2203 return a list of indices for @var{oldarray}, one for each dimension of
2206 @var{mapfunc} must be affine linear, meaning that each @var{oldarray}
2207 index must be formed by adding integer multiples (possibly negative)
2208 of some or all of @var{newidx1} etc, plus a possible integer offset.
2209 The multiples and offset must be the same in each call.
2212 One good use for a shared array is to restrict the range of some
2213 dimensions, so as to apply say @code{array-for-each} or
2214 @code{array-fill!} to only part of an array. The plain @code{list}
2215 function can be used for @var{mapfunc} in this case, making no changes
2216 to the index values. For example,
2219 (make-shared-array #2((a b c) (d e f) (g h i)) list 3 2)
2220 @result{} #2((a b) (d e) (g h))
2223 The new array can have fewer dimensions than @var{oldarray}, for
2224 example to take a column from an array.
2227 (make-shared-array #2((a b c) (d e f) (g h i))
2228 (lambda (i) (list i 2))
2233 A diagonal can be taken by using the single new array index for both
2234 row and column in the old array. For example,
2237 (make-shared-array #2((a b c) (d e f) (g h i))
2238 (lambda (i) (list i i))
2243 Dimensions can be increased by for instance considering portions of a
2244 one dimensional array as rows in a two dimensional array.
2245 (@code{array-contents} below can do the opposite, flattening an
2249 (make-shared-array #1(a b c d e f g h i j k l)
2250 (lambda (i j) (list (+ (* i 3) j)))
2252 @result{} #2((a b c) (d e f) (g h i) (j k l))
2255 By negating an index the order that elements appear can be reversed.
2256 The following just reverses the column order,
2259 (make-shared-array #2((a b c) (d e f) (g h i))
2260 (lambda (i j) (list i (- 2 j)))
2262 @result{} #2((c b a) (f e d) (i h g))
2265 A fixed offset on indexes allows for instance a change from a 0 based
2269 (define x #2((a b c) (d e f) (g h i)))
2270 (define y (make-shared-array x
2271 (lambda (i j) (list (1- i) (1- j)))
2273 (array-ref x 0 0) @result{} a
2274 (array-ref y 1 1) @result{} a
2277 A multiple on an index allows every Nth element of an array to be
2278 taken. The following is every third element,
2281 (make-shared-array #1(a b c d e f g h i j k l)
2282 (lambda (i) (list (* i 3)))
2284 @result{} #1(a d g j)
2287 The above examples can be combined to make weird and wonderful
2288 selections from an array, but it's important to note that because
2289 @var{mapfunc} must be affine linear, arbitrary permutations are not
2292 In the current implementation, @var{mapfunc} is not called for every
2293 access to the new array but only on some sample points to establish a
2294 base and stride for new array indices in @var{oldarray} data. A few
2295 sample points are enough because @var{mapfunc} is linear.
2298 @deffn {Scheme Procedure} shared-array-increments array
2299 @deffnx {C Function} scm_shared_array_increments (array)
2300 For each dimension, return the distance between elements in the root vector.
2303 @deffn {Scheme Procedure} shared-array-offset array
2304 @deffnx {C Function} scm_shared_array_offset (array)
2305 Return the root vector index of the first element in the array.
2308 @deffn {Scheme Procedure} shared-array-root array
2309 @deffnx {C Function} scm_shared_array_root (array)
2310 Return the root vector of a shared array.
2313 @deffn {Scheme Procedure} array-contents array [strict]
2314 @deffnx {C Function} scm_array_contents (array, strict)
2315 If @var{array} may be @dfn{unrolled} into a one dimensional shared array
2316 without changing their order (last subscript changing fastest), then
2317 @code{array-contents} returns that shared array, otherwise it returns
2318 @code{#f}. All arrays made by @code{make-array} and
2319 @code{make-typed-array} may be unrolled, some arrays made by
2320 @code{make-shared-array} may not be.
2322 If the optional argument @var{strict} is provided, a shared array will
2323 be returned only if its elements are stored internally contiguous in
2327 @deffn {Scheme Procedure} transpose-array array dim1 @dots{}
2328 @deffnx {C Function} scm_transpose_array (array, dimlist)
2329 Return an array sharing contents with @var{array}, but with
2330 dimensions arranged in a different order. There must be one
2331 @var{dim} argument for each dimension of @var{array}.
2332 @var{dim1}, @var{dim2}, @dots{} should be integers between 0
2333 and the rank of the array to be returned. Each integer in that
2334 range must appear at least once in the argument list.
2336 The values of @var{dim1}, @var{dim2}, @dots{} correspond to
2337 dimensions in the array to be returned, and their positions in the
2338 argument list to dimensions of @var{array}. Several @var{dim}s
2339 may have the same value, in which case the returned array will
2340 have smaller rank than @var{array}.
2343 (transpose-array '#2((a b) (c d)) 1 0) @result{} #2((a c) (b d))
2344 (transpose-array '#2((a b) (c d)) 0 0) @result{} #1(a d)
2345 (transpose-array '#3(((a b c) (d e f)) ((1 2 3) (4 5 6))) 1 1 0) @result{}
2346 #2((a 4) (b 5) (c 6))
2350 @node Accessing Arrays from C
2351 @subsubsection Accessing Arrays from C
2353 Arrays, especially uniform numeric arrays, are useful to efficiently
2354 represent large amounts of rectangularily organized information, such as
2355 matrices, images, or generally blobs of binary data. It is desirable to
2356 access these blobs in a C like manner so that they can be handed to
2357 external C code such as linear algebra libraries or image processing
2360 While pointers to the elements of an array are in use, the array itself
2361 must be protected so that the pointer remains valid. Such a protected
2362 array is said to be @dfn{reserved}. A reserved array can be read but
2363 modifications to it that would cause the pointer to its elements to
2364 become invalid are prevented. When you attempt such a modification, an
2367 (This is similar to locking the array while it is in use, but without
2368 the danger of a deadlock. In a multi-threaded program, you will need
2369 additional synchronization to avoid modifying reserved arrays.)
2371 You must take care to always unreserve an array after reserving it,
2372 even in the presence of non-local exits. If a non-local exit can
2373 happen between these two calls, you should install a dynwind context
2374 that releases the array when it is left (@pxref{Dynamic Wind}).
2376 In addition, array reserving and unreserving must be properly
2377 paired. For instance, when reserving two or more arrays in a certain
2378 order, you need to unreserve them in the opposite order.
2380 Once you have reserved an array and have retrieved the pointer to its
2381 elements, you must figure out the layout of the elements in memory.
2382 Guile allows slices to be taken out of arrays without actually making a
2383 copy, such as making an alias for the diagonal of a matrix that can be
2384 treated as a vector. Arrays that result from such an operation are not
2385 stored contiguously in memory and when working with their elements
2386 directly, you need to take this into account.
2388 The layout of array elements in memory can be defined via a
2389 @emph{mapping function} that computes a scalar position from a vector of
2390 indices. The scalar position then is the offset of the element with the
2391 given indices from the start of the storage block of the array.
2393 In Guile, this mapping function is restricted to be @dfn{affine}: all
2394 mapping functions of Guile arrays can be written as @code{p = b +
2395 c[0]*i[0] + c[1]*i[1] + ... + c[n-1]*i[n-1]} where @code{i[k]} is the
2396 @nicode{k}th index and @code{n} is the rank of the array. For
2397 example, a matrix of size 3x3 would have @code{b == 0}, @code{c[0] ==
2398 3} and @code{c[1] == 1}. When you transpose this matrix (with
2399 @code{transpose-array}, say), you will get an array whose mapping
2400 function has @code{b == 0}, @code{c[0] == 1} and @code{c[1] == 3}.
2402 The function @code{scm_array_handle_dims} gives you (indirect) access to
2403 the coefficients @code{c[k]}.
2406 Note that there are no functions for accessing the elements of a
2407 character array yet. Once the string implementation of Guile has been
2408 changed to use Unicode, we will provide them.
2410 @deftp {C Type} scm_t_array_handle
2411 This is a structure type that holds all information necessary to manage
2412 the reservation of arrays as explained above. Structures of this type
2413 must be allocated on the stack and must only be accessed by the
2414 functions listed below.
2417 @deftypefn {C Function} void scm_array_get_handle (SCM array, scm_t_array_handle *handle)
2418 Reserve @var{array}, which must be an array, and prepare @var{handle} to
2419 be used with the functions below. You must eventually call
2420 @code{scm_array_handle_release} on @var{handle}, and do this in a
2421 properly nested fashion, as explained above. The structure pointed to
2422 by @var{handle} does not need to be initialized before calling this
2426 @deftypefn {C Function} void scm_array_handle_release (scm_t_array_handle *handle)
2427 End the array reservation represented by @var{handle}. After a call to
2428 this function, @var{handle} might be used for another reservation.
2431 @deftypefn {C Function} size_t scm_array_handle_rank (scm_t_array_handle *handle)
2432 Return the rank of the array represented by @var{handle}.
2435 @deftp {C Type} scm_t_array_dim
2436 This structure type holds information about the layout of one dimension
2437 of an array. It includes the following fields:
2442 The lower and upper bounds (both inclusive) of the permissible index
2443 range for the given dimension. Both values can be negative, but
2444 @var{lbnd} is always less than or equal to @var{ubnd}.
2447 The distance from one element of this dimension to the next. Note, too,
2448 that this can be negative.
2452 @deftypefn {C Function} {const scm_t_array_dim *} scm_array_handle_dims (scm_t_array_handle *handle)
2453 Return a pointer to a C vector of information about the dimensions of
2454 the array represented by @var{handle}. This pointer is valid as long as
2455 the array remains reserved. As explained above, the
2456 @code{scm_t_array_dim} structures returned by this function can be used
2457 calculate the position of an element in the storage block of the array
2460 This position can then be used as an index into the C array pointer
2461 returned by the various @code{scm_array_handle_<foo>_elements}
2462 functions, or with @code{scm_array_handle_ref} and
2463 @code{scm_array_handle_set}.
2465 Here is how one can compute the position @var{pos} of an element given
2466 its indices in the vector @var{indices}:
2469 ssize_t indices[RANK];
2470 scm_t_array_dim *dims;
2475 for (i = 0; i < RANK; i++)
2477 if (indices[i] < dims[i].lbnd || indices[i] > dims[i].ubnd)
2479 pos += (indices[i] - dims[i].lbnd) * dims[i].inc;
2484 @deftypefn {C Function} ssize_t scm_array_handle_pos (scm_t_array_handle *handle, SCM indices)
2485 Compute the position corresponding to @var{indices}, a list of
2486 indices. The position is computed as described above for
2487 @code{scm_array_handle_dims}. The number of the indices and their
2488 range is checked and an appropriate error is signalled for invalid
2492 @deftypefn {C Function} SCM scm_array_handle_ref (scm_t_array_handle *handle, ssize_t pos)
2493 Return the element at position @var{pos} in the storage block of the
2494 array represented by @var{handle}. Any kind of array is acceptable. No
2495 range checking is done on @var{pos}.
2498 @deftypefn {C Function} void scm_array_handle_set (scm_t_array_handle *handle, ssize_t pos, SCM val)
2499 Set the element at position @var{pos} in the storage block of the array
2500 represented by @var{handle} to @var{val}. Any kind of array is
2501 acceptable. No range checking is done on @var{pos}. An error is
2502 signalled when the array can not store @var{val}.
2505 @deftypefn {C Function} {const SCM *} scm_array_handle_elements (scm_t_array_handle *handle)
2506 Return a pointer to the elements of a ordinary array of general Scheme
2507 values (i.e., a non-uniform array) for reading. This pointer is valid
2508 as long as the array remains reserved.
2511 @deftypefn {C Function} {SCM *} scm_array_handle_writable_elements (scm_t_array_handle *handle)
2512 Like @code{scm_array_handle_elements}, but the pointer is good for
2513 reading and writing.
2516 @deftypefn {C Function} {const void *} scm_array_handle_uniform_elements (scm_t_array_handle *handle)
2517 Return a pointer to the elements of a uniform numeric array for reading.
2518 This pointer is valid as long as the array remains reserved. The size
2519 of each element is given by @code{scm_array_handle_uniform_element_size}.
2522 @deftypefn {C Function} {void *} scm_array_handle_uniform_writable_elements (scm_t_array_handle *handle)
2523 Like @code{scm_array_handle_uniform_elements}, but the pointer is good
2524 reading and writing.
2527 @deftypefn {C Function} size_t scm_array_handle_uniform_element_size (scm_t_array_handle *handle)
2528 Return the size of one element of the uniform numeric array represented
2532 @deftypefn {C Function} {const scm_t_uint8 *} scm_array_handle_u8_elements (scm_t_array_handle *handle)
2533 @deftypefnx {C Function} {const scm_t_int8 *} scm_array_handle_s8_elements (scm_t_array_handle *handle)
2534 @deftypefnx {C Function} {const scm_t_uint16 *} scm_array_handle_u16_elements (scm_t_array_handle *handle)
2535 @deftypefnx {C Function} {const scm_t_int16 *} scm_array_handle_s16_elements (scm_t_array_handle *handle)
2536 @deftypefnx {C Function} {const scm_t_uint32 *} scm_array_handle_u32_elements (scm_t_array_handle *handle)
2537 @deftypefnx {C Function} {const scm_t_int32 *} scm_array_handle_s32_elements (scm_t_array_handle *handle)
2538 @deftypefnx {C Function} {const scm_t_uint64 *} scm_array_handle_u64_elements (scm_t_array_handle *handle)
2539 @deftypefnx {C Function} {const scm_t_int64 *} scm_array_handle_s64_elements (scm_t_array_handle *handle)
2540 @deftypefnx {C Function} {const float *} scm_array_handle_f32_elements (scm_t_array_handle *handle)
2541 @deftypefnx {C Function} {const double *} scm_array_handle_f64_elements (scm_t_array_handle *handle)
2542 @deftypefnx {C Function} {const float *} scm_array_handle_c32_elements (scm_t_array_handle *handle)
2543 @deftypefnx {C Function} {const double *} scm_array_handle_c64_elements (scm_t_array_handle *handle)
2544 Return a pointer to the elements of a uniform numeric array of the
2545 indicated kind for reading. This pointer is valid as long as the array
2548 The pointers for @code{c32} and @code{c64} uniform numeric arrays point
2549 to pairs of floating point numbers. The even index holds the real part,
2550 the odd index the imaginary part of the complex number.
2553 @deftypefn {C Function} {scm_t_uint8 *} scm_array_handle_u8_writable_elements (scm_t_array_handle *handle)
2554 @deftypefnx {C Function} {scm_t_int8 *} scm_array_handle_s8_writable_elements (scm_t_array_handle *handle)
2555 @deftypefnx {C Function} {scm_t_uint16 *} scm_array_handle_u16_writable_elements (scm_t_array_handle *handle)
2556 @deftypefnx {C Function} {scm_t_int16 *} scm_array_handle_s16_writable_elements (scm_t_array_handle *handle)
2557 @deftypefnx {C Function} {scm_t_uint32 *} scm_array_handle_u32_writable_elements (scm_t_array_handle *handle)
2558 @deftypefnx {C Function} {scm_t_int32 *} scm_array_handle_s32_writable_elements (scm_t_array_handle *handle)
2559 @deftypefnx {C Function} {scm_t_uint64 *} scm_array_handle_u64_writable_elements (scm_t_array_handle *handle)
2560 @deftypefnx {C Function} {scm_t_int64 *} scm_array_handle_s64_writable_elements (scm_t_array_handle *handle)
2561 @deftypefnx {C Function} {float *} scm_array_handle_f32_writable_elements (scm_t_array_handle *handle)
2562 @deftypefnx {C Function} {double *} scm_array_handle_f64_writable_elements (scm_t_array_handle *handle)
2563 @deftypefnx {C Function} {float *} scm_array_handle_c32_writable_elements (scm_t_array_handle *handle)
2564 @deftypefnx {C Function} {double *} scm_array_handle_c64_writable_elements (scm_t_array_handle *handle)
2565 Like @code{scm_array_handle_<kind>_elements}, but the pointer is good
2566 for reading and writing.
2569 @deftypefn {C Function} {const scm_t_uint32 *} scm_array_handle_bit_elements (scm_t_array_handle *handle)
2570 Return a pointer to the words that store the bits of the represented
2571 array, which must be a bit array.
2573 Unlike other arrays, bit arrays have an additional offset that must be
2574 figured into index calculations. That offset is returned by
2575 @code{scm_array_handle_bit_elements_offset}.
2577 To find a certain bit you first need to calculate its position as
2578 explained above for @code{scm_array_handle_dims} and then add the
2579 offset. This gives the absolute position of the bit, which is always a
2580 non-negative integer.
2582 Each word of the bit array storage block contains exactly 32 bits, with
2583 the least significant bit in that word having the lowest absolute
2584 position number. The next word contains the next 32 bits.
2586 Thus, the following code can be used to access a bit whose position
2587 according to @code{scm_array_handle_dims} is given in @var{pos}:
2591 scm_t_array_handle handle;
2595 size_t word_pos, mask;
2597 scm_array_get_handle (&bit_array, &handle);
2598 bits = scm_array_handle_bit_elements (&handle);
2601 abs_pos = pos + scm_array_handle_bit_elements_offset (&handle);
2602 word_pos = abs_pos / 32;
2603 mask = 1L << (abs_pos % 32);
2605 if (bits[word_pos] & mask)
2608 scm_array_handle_release (&handle);
2613 @deftypefn {C Function} {scm_t_uint32 *} scm_array_handle_bit_writable_elements (scm_t_array_handle *handle)
2614 Like @code{scm_array_handle_bit_elements} but the pointer is good for
2615 reading and writing. You must take care not to modify bits outside of
2616 the allowed index range of the array, even for contiguous arrays.
2622 A @dfn{record type} is a first class object representing a user-defined
2623 data type. A @dfn{record} is an instance of a record type.
2625 @deffn {Scheme Procedure} record? obj
2626 Return @code{#t} if @var{obj} is a record of any type and @code{#f}
2629 Note that @code{record?} may be true of any Scheme value; there is no
2630 promise that records are disjoint with other Scheme types.
2633 @deffn {Scheme Procedure} make-record-type type-name field-names [print]
2634 Create and return a new @dfn{record-type descriptor}.
2636 @var{type-name} is a string naming the type. Currently it's only used
2637 in the printed representation of records, and in diagnostics.
2638 @var{field-names} is a list of symbols naming the fields of a record
2639 of the type. Duplicates are not allowed among these symbols.
2642 (make-record-type "employee" '(name age salary))
2645 The optional @var{print} argument is a function used by
2646 @code{display}, @code{write}, etc, for printing a record of the new
2647 type. It's called as @code{(@var{print} record port)} and should look
2648 at @var{record} and write to @var{port}.
2651 @deffn {Scheme Procedure} record-constructor rtd [field-names]
2652 Return a procedure for constructing new members of the type represented
2653 by @var{rtd}. The returned procedure accepts exactly as many arguments
2654 as there are symbols in the given list, @var{field-names}; these are
2655 used, in order, as the initial values of those fields in a new record,
2656 which is returned by the constructor procedure. The values of any
2657 fields not named in that list are unspecified. The @var{field-names}
2658 argument defaults to the list of field names in the call to
2659 @code{make-record-type} that created the type represented by @var{rtd};
2660 if the @var{field-names} argument is provided, it is an error if it
2661 contains any duplicates or any symbols not in the default list.
2664 @deffn {Scheme Procedure} record-predicate rtd
2665 Return a procedure for testing membership in the type represented by
2666 @var{rtd}. The returned procedure accepts exactly one argument and
2667 returns a true value if the argument is a member of the indicated record
2668 type; it returns a false value otherwise.
2671 @deffn {Scheme Procedure} record-accessor rtd field-name
2672 Return a procedure for reading the value of a particular field of a
2673 member of the type represented by @var{rtd}. The returned procedure
2674 accepts exactly one argument which must be a record of the appropriate
2675 type; it returns the current value of the field named by the symbol
2676 @var{field-name} in that record. The symbol @var{field-name} must be a
2677 member of the list of field-names in the call to @code{make-record-type}
2678 that created the type represented by @var{rtd}.
2681 @deffn {Scheme Procedure} record-modifier rtd field-name
2682 Return a procedure for writing the value of a particular field of a
2683 member of the type represented by @var{rtd}. The returned procedure
2684 accepts exactly two arguments: first, a record of the appropriate type,
2685 and second, an arbitrary Scheme value; it modifies the field named by
2686 the symbol @var{field-name} in that record to contain the given value.
2687 The returned value of the modifier procedure is unspecified. The symbol
2688 @var{field-name} must be a member of the list of field-names in the call
2689 to @code{make-record-type} that created the type represented by
2693 @deffn {Scheme Procedure} record-type-descriptor record
2694 Return a record-type descriptor representing the type of the given
2695 record. That is, for example, if the returned descriptor were passed to
2696 @code{record-predicate}, the resulting predicate would return a true
2697 value when passed the given record. Note that it is not necessarily the
2698 case that the returned descriptor is the one that was passed to
2699 @code{record-constructor} in the call that created the constructor
2700 procedure that created the given record.
2703 @deffn {Scheme Procedure} record-type-name rtd
2704 Return the type-name associated with the type represented by rtd. The
2705 returned value is @code{eqv?} to the @var{type-name} argument given in
2706 the call to @code{make-record-type} that created the type represented by
2710 @deffn {Scheme Procedure} record-type-fields rtd
2711 Return a list of the symbols naming the fields in members of the type
2712 represented by @var{rtd}. The returned value is @code{equal?} to the
2713 field-names argument given in the call to @code{make-record-type} that
2714 created the type represented by @var{rtd}.
2719 @subsection Structures
2722 A @dfn{structure} is a first class data type which holds Scheme values
2723 or C words in fields numbered 0 upwards. A @dfn{vtable} represents a
2724 structure type, giving field types and permissions, and an optional
2725 print function for @code{write} etc.
2727 Structures are lower level than records (@pxref{Records}) but have
2728 some extra features. The vtable system allows sets of types be
2729 constructed, with class data. The uninterpreted words can
2730 inter-operate with C code, allowing arbitrary pointers or other values
2731 to be stored along side usual Scheme @code{SCM} values.
2735 * Structure Basics::
2740 @node Vtables, Structure Basics, Structures, Structures
2741 @subsubsection Vtables
2743 A vtable is a structure type, specifying its layout, and other
2744 information. A vtable is actually itself a structure, but there's no
2745 need to worray about that initially (@pxref{Vtable Contents}.)
2747 @deffn {Scheme Procedure} make-vtable fields [print]
2748 Create a new vtable.
2750 @var{fields} is a string describing the fields in the structures to be
2751 created. Each field is represented by two characters, a type letter
2752 and a permissions letter, for example @code{"pw"}. The types are as
2757 @code{p} -- a Scheme value. ``p'' stands for ``protected'' meaning
2758 it's protected against garbage collection.
2761 @code{u} -- an arbitrary word of data (an @code{scm_t_bits}). At the
2762 Scheme level it's read and written as an unsigned integer. ``u''
2763 stands for ``uninterpreted'' (it's not treated as a Scheme value), or
2764 ``unprotected'' (it's not marked during GC), or ``unsigned long'' (its
2765 size), or all of these things.
2768 @code{s} -- a self-reference. Such a field holds the @code{SCM} value
2769 of the structure itself (a circular reference). This can be useful in
2770 C code where you might have a pointer to the data array, and want to
2771 get the Scheme @code{SCM} handle for the structure. In Scheme code it
2775 The second letter for each field is a permission code,
2779 @code{w} -- writable, the field can be read and written.
2781 @code{r} -- read-only, the field can be read but not written.
2783 @code{o} -- opaque, the field can be neither read nor written at the
2784 Scheme level. This can be used for fields which should only be used
2787 @code{W},@code{R},@code{O} -- a tail array, with permissions for the
2788 array fields as per @code{w},@code{r},@code{o}.
2791 A tail array is further fields at the end of a structure. The last
2792 field in the layout string might be for instance @samp{pW} to have a
2793 tail of writable Scheme-valued fields. The @samp{pW} field itself
2794 holds the tail size, and the tail fields come after it.
2796 Here are some examples.
2799 (make-vtable "pw") ;; one writable field
2800 (make-vtable "prpw") ;; one read-only and one writable
2801 (make-vtable "pwuwuw") ;; one scheme and two uninterpreted
2803 (make-vtable "prpW") ;; one fixed then a tail array
2806 The optional @var{print} argument is a function called by
2807 @code{display} and @code{write} (etc) to give a printed representation
2808 of a structure created from this vtable. It's called
2809 @code{(@var{print} struct port)} and should look at @var{struct} and
2810 write to @var{port}. The default print merely gives a form like
2811 @samp{#<struct ADDR:ADDR>} with a pair of machine addresses.
2813 The following print function for example shows the two fields of its
2818 (lambda (struct port)
2820 (display (struct-ref struct 0) port)
2821 (display " and " port)
2822 (display (struct-ref struct 1) port)
2823 (display ">" port)))
2828 @node Structure Basics, Vtable Contents, Vtables, Structures
2829 @subsubsection Structure Basics
2831 This section describes the basic procedures for working with
2832 structures. @code{make-struct} creates a structure, and
2833 @code{struct-ref} and @code{struct-set!} access write fields.
2835 @deffn {Scheme Procedure} make-struct vtable tail-size [init...]
2836 @deffnx {C Function} scm_make_struct (vtable, tail_size, init_list)
2837 Create a new structure, with layout per the given @var{vtable}
2840 @var{tail-size} is the size of the tail array if @var{vtable}
2841 specifies a tail array. @var{tail-size} should be 0 when @var{vtable}
2842 doesn't specify a tail array.
2844 The optional @var{init}@dots{} arguments are initial values for the
2845 fields of the structure (and the tail array). This is the only way to
2846 put values in read-only fields. If there are fewer @var{init}
2847 arguments than fields then the defaults are @code{#f} for a Scheme
2848 field (type @code{p}) or 0 for an uninterpreted field (type @code{u}).
2850 Type @code{s} self-reference fields, permission @code{o} opaque
2851 fields, and the count field of a tail array are all ignored for the
2852 @var{init} arguments, ie.@: an argument is not consumed by such a
2853 field. An @code{s} is always set to the structure itself, an @code{o}
2854 is always set to @code{#f} or 0 (with the intention that C code will
2855 do something to it later), and the tail count is always the given
2861 (define v (make-vtable "prpwpw"))
2862 (define s (make-struct v 0 123 "abc" 456))
2863 (struct-ref s 0) @result{} 123
2864 (struct-ref s 1) @result{} "abc"
2868 (define v (make-vtable "prpW"))
2869 (define s (make-struct v 6 "fixed field" 'x 'y))
2870 (struct-ref s 0) @result{} "fixed field"
2871 (struct-ref s 1) @result{} 2 ;; tail size
2872 (struct-ref s 2) @result{} x ;; tail array ...
2873 (struct-ref s 3) @result{} y
2874 (struct-ref s 4) @result{} #f
2878 @deffn {Scheme Procedure} struct? obj
2879 @deffnx {C Function} scm_struct_p (obj)
2880 Return @code{#t} if @var{obj} is a structure, or @code{#f} if not.
2883 @deffn {Scheme Procedure} struct-ref struct n
2884 @deffnx {C Function} scm_struct_ref (struct, n)
2885 Return the contents of field number @var{n} in @var{struct}. The
2886 first field is number 0.
2888 An error is thrown if @var{n} is out of range, or if the field cannot
2889 be read because it's @code{o} opaque.
2892 @deffn {Scheme Procedure} struct-set! struct n value
2893 @deffnx {C Function} scm_struct_set_x (struct, n, value)
2894 Set field number @var{n} in @var{struct} to @var{value}. The first
2897 An error is thrown if @var{n} is out of range, or if the field cannot
2898 be written because it's @code{r} read-only or @code{o} opaque.
2901 @deffn {Scheme Procedure} struct-vtable struct
2902 @deffnx {C Function} scm_struct_vtable (struct)
2903 Return the vtable used by @var{struct}.
2905 This can be used to examine the layout of an unknown structure, see
2906 @ref{Vtable Contents}.
2910 @node Vtable Contents, Vtable Vtables, Structure Basics, Structures
2911 @subsubsection Vtable Contents
2913 A vtable is itself a structure, with particular fields that hold
2914 information about the structures to be created. These include the
2915 fields of those structures, and the print function for them. The
2916 variables below allow access to those fields.
2918 @deffn {Scheme Procedure} struct-vtable? obj
2919 @deffnx {C Function} scm_struct_vtable_p (obj)
2920 Return @code{#t} if @var{obj} is a vtable structure.
2922 Note that because vtables are simply structures with a particular
2923 layout, @code{struct-vtable?} can potentially return true on an
2924 application structure which merely happens to look like a vtable.
2927 @defvr {Scheme Variable} vtable-index-layout
2928 @defvrx {C Macro} scm_vtable_index_layout
2929 The field number of the layout specification in a vtable. The layout
2930 specification is a symbol like @code{pwpw} formed from the fields
2931 string passed to @code{make-vtable}, or created by
2932 @code{make-struct-layout} (@pxref{Vtable Vtables}).
2935 (define v (make-vtable "pwpw" 0))
2936 (struct-ref v vtable-index-layout) @result{} pwpw
2939 This field is read-only, since the layout of structures using a vtable
2943 @defvr {Scheme Variable} vtable-index-vtable
2944 @defvrx {C Macro} scm_vtable_index_vtable
2945 A self-reference to the vtable, ie.@: a type @code{s} field. This is
2946 used by C code within Guile and has no use at the Scheme level.
2949 @defvr {Scheme Variable} vtable-index-printer
2950 @defvrx {C Macro} scm_vtable_index_printer
2951 The field number of the printer function. This field contains @code{#f}
2952 if the default print function should be used.
2955 (define (my-print-func struct port)
2957 (define v (make-vtable "pwpw" my-print-func))
2958 (struct-ref v vtable-index-printer) @result{} my-print-func
2961 This field is writable, allowing the print function to be changed
2965 @deffn {Scheme Procedure} struct-vtable-name vtable
2966 @deffnx {Scheme Procedure} set-struct-vtable-name! vtable name
2967 @deffnx {C Function} scm_struct_vtable_name (vtable)
2968 @deffnx {C Function} scm_set_struct_vtable_name_x (vtable, name)
2969 Get or set the name of @var{vtable}. @var{name} is a symbol and is
2970 used in the default print function when printing structures created
2974 (define v (make-vtable "pw"))
2975 (set-struct-vtable-name! v 'my-name)
2977 (define s (make-struct v 0))
2978 (display s) @print{} #<my-name b7ab3ae0:b7ab3730>
2982 @deffn {Scheme Procedure} struct-vtable-tag vtable
2983 @deffnx {C Function} scm_struct_vtable_tag (vtable)
2984 Return the tag of the given @var{vtable}.
2986 @c FIXME: what can be said about what this means?
2991 @node Vtable Vtables, , Vtable Contents, Structures
2992 @subsubsection Vtable Vtables
2994 As noted above, a vtable is a structure and that structure is itself
2995 described by a vtable. Such a ``vtable of a vtable'' can be created
2996 with @code{make-vtable-vtable} below. This can be used to build sets
2997 of related vtables, possibly with extra application fields.
2999 This second level of vtable can be a little confusing. The ball
3000 example below is a typical use, adding a ``class data'' field to the
3001 vtables, from which instance structures are created. The current
3002 implementation of Guile's own records (@pxref{Records}) does something
3003 similar, a record type descriptor is a vtable with room to hold the
3004 field names of the records to be created from it.
3006 @deffn {Scheme Procedure} make-vtable-vtable user-fields tail-size [print]
3007 @deffnx {C Function} scm_make_vtable_vtable (user_fields, tail_size, print_and_init_list)
3008 Create a ``vtable-vtable'' which can be used to create vtables. This
3009 vtable-vtable is also a vtable, and is self-describing, meaning its
3010 vtable is itself. The following is a simple usage.
3013 (define vt-vt (make-vtable-vtable "" 0))
3014 (define vt (make-struct vt-vt 0
3015 (make-struct-layout "pwpw"))
3016 (define s (make-struct vt 0 123 456))
3018 (struct-ref s 0) @result{} 123
3021 @code{make-struct} is used to create a vtable from the vtable-vtable.
3022 The first initializer is a layout object (field
3023 @code{vtable-index-layout}), usually obtained from
3024 @code{make-struct-layout} (below). An optional second initializer is
3025 a printer function (field @code{vtable-index-printer}), used as
3026 described under @code{make-vtable} (@pxref{Vtables}).
3029 @var{user-fields} is a layout string giving extra fields to have in
3030 the vtables. A vtable starts with some base fields as per @ref{Vtable
3031 Contents}, and @var{user-fields} is appended. The @var{user-fields}
3032 start at field number @code{vtable-offset-user} (below), and exist in
3033 both the vtable-vtable and in the vtables created from it. Such
3034 fields provide space for ``class data''. For example,
3037 (define vt-of-vt (make-vtable-vtable "pw" 0))
3038 (define vt (make-struct vt-of-vt 0))
3039 (struct-set! vt vtable-offset-user "my class data")
3042 @var{tail-size} is the size of the tail array in the vtable-vtable
3043 itself, if @var{user-fields} specifies a tail array. This should be 0
3044 if nothing extra is required or the format has no tail array. The
3045 tail array field such as @samp{pW} holds the tail array size, as
3046 usual, and is followed by the extra space.
3049 (define vt-vt (make-vtable-vtable "pW" 20))
3050 (define my-vt-tail-start (1+ vtable-offset-user))
3051 (struct-set! vt-vt (+ 3 my-vt-tail-start) "data in tail")
3054 The optional @var{print} argument is used by @code{display} and
3055 @code{write} (etc) to print the vtable-vtable and any vtables created
3056 from it. It's called as @code{(@var{print} vtable port)} and should
3057 look at @var{vtable} and write to @var{port}. The default is the
3058 usual structure print function, which just gives machine addresses.
3061 @deffn {Scheme Procedure} make-struct-layout fields
3062 @deffnx {C Function} scm_make_struct_layout (fields)
3063 Return a structure layout symbol, from a @var{fields} string.
3064 @var{fields} is as described under @code{make-vtable}
3065 (@pxref{Vtables}). An invalid @var{fields} string is an error.
3068 (make-struct-layout "prpW") @result{} prpW
3069 (make-struct-layout "blah") @result{} ERROR
3073 @defvr {Scheme Variable} vtable-offset-user
3074 @defvrx {C Macro} scm_vtable_offset_user
3075 The first field in a vtable which is available for application use.
3076 Such fields only exist when specified by @var{user-fields} in
3077 @code{make-vtable-vtable} above.
3081 Here's an extended vtable-vtable example, creating classes of
3082 ``balls''. Each class has a ``colour'', which is fixed. Instances of
3083 those classes are created, and such each such ball has an ``owner'',
3084 which can be changed.
3087 (define ball-root (make-vtable-vtable "pr" 0))
3089 (define (make-ball-type ball-color)
3090 (make-struct ball-root 0
3091 (make-struct-layout "pw")
3093 (format port "#<a ~A ball owned by ~A>"
3097 (define (color ball)
3098 (struct-ref (struct-vtable ball) vtable-offset-user))
3099 (define (owner ball)
3100 (struct-ref ball 0))
3102 (define red (make-ball-type 'red))
3103 (define green (make-ball-type 'green))
3105 (define (make-ball type owner) (make-struct type 0 owner))
3107 (define ball (make-ball green 'Nisse))
3108 ball @result{} #<a green ball owned by Nisse>
3112 @node Dictionary Types
3113 @subsection Dictionary Types
3115 A @dfn{dictionary} object is a data structure used to index
3116 information in a user-defined way. In standard Scheme, the main
3117 aggregate data types are lists and vectors. Lists are not really
3118 indexed at all, and vectors are indexed only by number
3119 (e.g. @code{(vector-ref foo 5)}). Often you will find it useful
3120 to index your data on some other type; for example, in a library
3121 catalog you might want to look up a book by the name of its
3122 author. Dictionaries are used to help you organize information in
3125 An @dfn{association list} (or @dfn{alist} for short) is a list of
3126 key-value pairs. Each pair represents a single quantity or
3127 object; the @code{car} of the pair is a key which is used to
3128 identify the object, and the @code{cdr} is the object's value.
3130 A @dfn{hash table} also permits you to index objects with
3131 arbitrary keys, but in a way that makes looking up any one object
3132 extremely fast. A well-designed hash system makes hash table
3133 lookups almost as fast as conventional array or vector references.
3135 Alists are popular among Lisp programmers because they use only
3136 the language's primitive operations (lists, @dfn{car}, @dfn{cdr}
3137 and the equality primitives). No changes to the language core are
3138 necessary. Therefore, with Scheme's built-in list manipulation
3139 facilities, it is very convenient to handle data stored in an
3140 association list. Also, alists are highly portable and can be
3141 easily implemented on even the most minimal Lisp systems.
3143 However, alists are inefficient, especially for storing large
3144 quantities of data. Because we want Guile to be useful for large
3145 software systems as well as small ones, Guile provides a rich set
3146 of tools for using either association lists or hash tables.
3148 @node Association Lists
3149 @subsection Association Lists
3150 @tpindex Association Lists
3152 @cindex association List
3156 An association list is a conventional data structure that is often used
3157 to implement simple key-value databases. It consists of a list of
3158 entries in which each entry is a pair. The @dfn{key} of each entry is
3159 the @code{car} of the pair and the @dfn{value} of each entry is the
3163 ASSOCIATION LIST ::= '( (KEY1 . VALUE1)
3171 Association lists are also known, for short, as @dfn{alists}.
3173 The structure of an association list is just one example of the infinite
3174 number of possible structures that can be built using pairs and lists.
3175 As such, the keys and values in an association list can be manipulated
3176 using the general list structure procedures @code{cons}, @code{car},
3177 @code{cdr}, @code{set-car!}, @code{set-cdr!} and so on. However,
3178 because association lists are so useful, Guile also provides specific
3179 procedures for manipulating them.
3182 * Alist Key Equality::
3183 * Adding or Setting Alist Entries::
3184 * Retrieving Alist Entries::
3185 * Removing Alist Entries::
3186 * Sloppy Alist Functions::
3190 @node Alist Key Equality
3191 @subsubsection Alist Key Equality
3193 All of Guile's dedicated association list procedures, apart from
3194 @code{acons}, come in three flavours, depending on the level of equality
3195 that is required to decide whether an existing key in the association
3196 list is the same as the key that the procedure call uses to identify the
3201 Procedures with @dfn{assq} in their name use @code{eq?} to determine key
3205 Procedures with @dfn{assv} in their name use @code{eqv?} to determine
3209 Procedures with @dfn{assoc} in their name use @code{equal?} to
3210 determine key equality.
3213 @code{acons} is an exception because it is used to build association
3214 lists which do not require their entries' keys to be unique.
3216 @node Adding or Setting Alist Entries
3217 @subsubsection Adding or Setting Alist Entries
3219 @code{acons} adds a new entry to an association list and returns the
3220 combined association list. The combined alist is formed by consing the
3221 new entry onto the head of the alist specified in the @code{acons}
3222 procedure call. So the specified alist is not modified, but its
3223 contents become shared with the tail of the combined alist that
3224 @code{acons} returns.
3226 In the most common usage of @code{acons}, a variable holding the
3227 original association list is updated with the combined alist:
3230 (set! address-list (acons name address address-list))
3233 In such cases, it doesn't matter that the old and new values of
3234 @code{address-list} share some of their contents, since the old value is
3235 usually no longer independently accessible.
3237 Note that @code{acons} adds the specified new entry regardless of
3238 whether the alist may already contain entries with keys that are, in
3239 some sense, the same as that of the new entry. Thus @code{acons} is
3240 ideal for building alists where there is no concept of key uniqueness.
3243 (set! task-list (acons 3 "pay gas bill" '()))
3246 ((3 . "pay gas bill"))
3248 (set! task-list (acons 3 "tidy bedroom" task-list))
3251 ((3 . "tidy bedroom") (3 . "pay gas bill"))
3254 @code{assq-set!}, @code{assv-set!} and @code{assoc-set!} are used to add
3255 or replace an entry in an association list where there @emph{is} a
3256 concept of key uniqueness. If the specified association list already
3257 contains an entry whose key is the same as that specified in the
3258 procedure call, the existing entry is replaced by the new one.
3259 Otherwise, the new entry is consed onto the head of the old association
3260 list to create the combined alist. In all cases, these procedures
3261 return the combined alist.
3263 @code{assq-set!} and friends @emph{may} destructively modify the
3264 structure of the old association list in such a way that an existing
3265 variable is correctly updated without having to @code{set!} it to the
3271 (("mary" . "34 Elm Road") ("james" . "16 Bow Street"))
3273 (assoc-set! address-list "james" "1a London Road")
3275 (("mary" . "34 Elm Road") ("james" . "1a London Road"))
3279 (("mary" . "34 Elm Road") ("james" . "1a London Road"))
3285 (assoc-set! address-list "bob" "11 Newington Avenue")
3287 (("bob" . "11 Newington Avenue") ("mary" . "34 Elm Road")
3288 ("james" . "1a London Road"))
3292 (("mary" . "34 Elm Road") ("james" . "1a London Road"))
3295 The only safe way to update an association list variable when adding or
3296 replacing an entry like this is to @code{set!} the variable to the
3301 (assoc-set! address-list "bob" "11 Newington Avenue"))
3304 (("bob" . "11 Newington Avenue") ("mary" . "34 Elm Road")
3305 ("james" . "1a London Road"))
3308 Because of this slight inconvenience, you may find it more convenient to
3309 use hash tables to store dictionary data. If your application will not
3310 be modifying the contents of an alist very often, this may not make much
3313 If you need to keep the old value of an association list in a form
3314 independent from the list that results from modification by
3315 @code{acons}, @code{assq-set!}, @code{assv-set!} or @code{assoc-set!},
3316 use @code{list-copy} to copy the old association list before modifying
3319 @deffn {Scheme Procedure} acons key value alist
3320 @deffnx {C Function} scm_acons (key, value, alist)
3321 Add a new key-value pair to @var{alist}. A new pair is
3322 created whose car is @var{key} and whose cdr is @var{value}, and the
3323 pair is consed onto @var{alist}, and the new list is returned. This
3324 function is @emph{not} destructive; @var{alist} is not modified.
3327 @deffn {Scheme Procedure} assq-set! alist key val
3328 @deffnx {Scheme Procedure} assv-set! alist key value
3329 @deffnx {Scheme Procedure} assoc-set! alist key value
3330 @deffnx {C Function} scm_assq_set_x (alist, key, val)
3331 @deffnx {C Function} scm_assv_set_x (alist, key, val)
3332 @deffnx {C Function} scm_assoc_set_x (alist, key, val)
3333 Reassociate @var{key} in @var{alist} with @var{value}: find any existing
3334 @var{alist} entry for @var{key} and associate it with the new
3335 @var{value}. If @var{alist} does not contain an entry for @var{key},
3336 add a new one. Return the (possibly new) alist.
3338 These functions do not attempt to verify the structure of @var{alist},
3339 and so may cause unusual results if passed an object that is not an
3343 @node Retrieving Alist Entries
3344 @subsubsection Retrieving Alist Entries
3349 @code{assq}, @code{assv} and @code{assoc} find the entry in an alist
3350 for a given key, and return the @code{(@var{key} . @var{value})} pair.
3351 @code{assq-ref}, @code{assv-ref} and @code{assoc-ref} do a similar
3352 lookup, but return just the @var{value}.
3354 @deffn {Scheme Procedure} assq key alist
3355 @deffnx {Scheme Procedure} assv key alist
3356 @deffnx {Scheme Procedure} assoc key alist
3357 @deffnx {C Function} scm_assq (key, alist)
3358 @deffnx {C Function} scm_assv (key, alist)
3359 @deffnx {C Function} scm_assoc (key, alist)
3360 Return the first entry in @var{alist} with the given @var{key}. The
3361 return is the pair @code{(KEY . VALUE)} from @var{alist}. If there's
3362 no matching entry the return is @code{#f}.
3364 @code{assq} compares keys with @code{eq?}, @code{assv} uses
3365 @code{eqv?} and @code{assoc} uses @code{equal?}. See also SRFI-1
3366 which has an extended @code{assoc} (@ref{SRFI-1 Association Lists}).
3369 @deffn {Scheme Procedure} assq-ref alist key
3370 @deffnx {Scheme Procedure} assv-ref alist key
3371 @deffnx {Scheme Procedure} assoc-ref alist key
3372 @deffnx {C Function} scm_assq_ref (alist, key)
3373 @deffnx {C Function} scm_assv_ref (alist, key)
3374 @deffnx {C Function} scm_assoc_ref (alist, key)
3375 Return the value from the first entry in @var{alist} with the given
3376 @var{key}, or @code{#f} if there's no such entry.
3378 @code{assq-ref} compares keys with @code{eq?}, @code{assv-ref} uses
3379 @code{eqv?} and @code{assoc-ref} uses @code{equal?}.
3381 Notice these functions have the @var{key} argument last, like other
3382 @code{-ref} functions, but this is opposite to what @code{assq}
3385 When the return is @code{#f} it can be either @var{key} not found, or
3386 an entry which happens to have value @code{#f} in the @code{cdr}. Use
3387 @code{assq} etc above if you need to differentiate these cases.
3391 @node Removing Alist Entries
3392 @subsubsection Removing Alist Entries
3394 To remove the element from an association list whose key matches a
3395 specified key, use @code{assq-remove!}, @code{assv-remove!} or
3396 @code{assoc-remove!} (depending, as usual, on the level of equality
3397 required between the key that you specify and the keys in the
3400 As with @code{assq-set!} and friends, the specified alist may or may not
3401 be modified destructively, and the only safe way to update a variable
3402 containing the alist is to @code{set!} it to the value that
3403 @code{assq-remove!} and friends return.
3408 (("bob" . "11 Newington Avenue") ("mary" . "34 Elm Road")
3409 ("james" . "1a London Road"))
3411 (set! address-list (assoc-remove! address-list "mary"))
3414 (("bob" . "11 Newington Avenue") ("james" . "1a London Road"))
3417 Note that, when @code{assq/v/oc-remove!} is used to modify an
3418 association list that has been constructed only using the corresponding
3419 @code{assq/v/oc-set!}, there can be at most one matching entry in the
3420 alist, so the question of multiple entries being removed in one go does
3421 not arise. If @code{assq/v/oc-remove!} is applied to an association
3422 list that has been constructed using @code{acons}, or an
3423 @code{assq/v/oc-set!} with a different level of equality, or any mixture
3424 of these, it removes only the first matching entry from the alist, even
3425 if the alist might contain further matching entries. For example:
3428 (define address-list '())
3429 (set! address-list (assq-set! address-list "mary" "11 Elm Street"))
3430 (set! address-list (assq-set! address-list "mary" "57 Pine Drive"))
3433 (("mary" . "57 Pine Drive") ("mary" . "11 Elm Street"))
3435 (set! address-list (assoc-remove! address-list "mary"))
3438 (("mary" . "11 Elm Street"))
3441 In this example, the two instances of the string "mary" are not the same
3442 when compared using @code{eq?}, so the two @code{assq-set!} calls add
3443 two distinct entries to @code{address-list}. When compared using
3444 @code{equal?}, both "mary"s in @code{address-list} are the same as the
3445 "mary" in the @code{assoc-remove!} call, but @code{assoc-remove!} stops
3446 after removing the first matching entry that it finds, and so one of the
3447 "mary" entries is left in place.
3449 @deffn {Scheme Procedure} assq-remove! alist key
3450 @deffnx {Scheme Procedure} assv-remove! alist key
3451 @deffnx {Scheme Procedure} assoc-remove! alist key
3452 @deffnx {C Function} scm_assq_remove_x (alist, key)
3453 @deffnx {C Function} scm_assv_remove_x (alist, key)
3454 @deffnx {C Function} scm_assoc_remove_x (alist, key)
3455 Delete the first entry in @var{alist} associated with @var{key}, and return
3456 the resulting alist.
3459 @node Sloppy Alist Functions
3460 @subsubsection Sloppy Alist Functions
3462 @code{sloppy-assq}, @code{sloppy-assv} and @code{sloppy-assoc} behave
3463 like the corresponding non-@code{sloppy-} procedures, except that they
3464 return @code{#f} when the specified association list is not well-formed,
3465 where the non-@code{sloppy-} versions would signal an error.
3467 Specifically, there are two conditions for which the non-@code{sloppy-}
3468 procedures signal an error, which the @code{sloppy-} procedures handle
3469 instead by returning @code{#f}. Firstly, if the specified alist as a
3470 whole is not a proper list:
3473 (assoc "mary" '((1 . 2) ("key" . "door") . "open sesame"))
3475 ERROR: In procedure assoc in expression (assoc "mary" (quote #)):
3476 ERROR: Wrong type argument in position 2 (expecting
3477 association list): ((1 . 2) ("key" . "door") . "open sesame")
3479 (sloppy-assoc "mary" '((1 . 2) ("key" . "door") . "open sesame"))
3485 Secondly, if one of the entries in the specified alist is not a pair:
3488 (assoc 2 '((1 . 1) 2 (3 . 9)))
3490 ERROR: In procedure assoc in expression (assoc 2 (quote #)):
3491 ERROR: Wrong type argument in position 2 (expecting
3492 association list): ((1 . 1) 2 (3 . 9))
3494 (sloppy-assoc 2 '((1 . 1) 2 (3 . 9)))
3499 Unless you are explicitly working with badly formed association lists,
3500 it is much safer to use the non-@code{sloppy-} procedures, because they
3501 help to highlight coding and data errors that the @code{sloppy-}
3502 versions would silently cover up.
3504 @deffn {Scheme Procedure} sloppy-assq key alist
3505 @deffnx {C Function} scm_sloppy_assq (key, alist)
3506 Behaves like @code{assq} but does not do any error checking.
3507 Recommended only for use in Guile internals.
3510 @deffn {Scheme Procedure} sloppy-assv key alist
3511 @deffnx {C Function} scm_sloppy_assv (key, alist)
3512 Behaves like @code{assv} but does not do any error checking.
3513 Recommended only for use in Guile internals.
3516 @deffn {Scheme Procedure} sloppy-assoc key alist
3517 @deffnx {C Function} scm_sloppy_assoc (key, alist)
3518 Behaves like @code{assoc} but does not do any error checking.
3519 Recommended only for use in Guile internals.
3523 @subsubsection Alist Example
3525 Here is a longer example of how alists may be used in practice.
3528 (define capitals '(("New York" . "Albany")
3529 ("Oregon" . "Salem")
3530 ("Florida" . "Miami")))
3532 ;; What's the capital of Oregon?
3533 (assoc "Oregon" capitals) @result{} ("Oregon" . "Salem")
3534 (assoc-ref capitals "Oregon") @result{} "Salem"
3536 ;; We left out South Dakota.
3538 (assoc-set! capitals "South Dakota" "Pierre"))
3540 @result{} (("South Dakota" . "Pierre")
3541 ("New York" . "Albany")
3542 ("Oregon" . "Salem")
3543 ("Florida" . "Miami"))
3545 ;; And we got Florida wrong.
3547 (assoc-set! capitals "Florida" "Tallahassee"))
3549 @result{} (("South Dakota" . "Pierre")
3550 ("New York" . "Albany")
3551 ("Oregon" . "Salem")
3552 ("Florida" . "Tallahassee"))
3554 ;; After Oregon secedes, we can remove it.
3556 (assoc-remove! capitals "Oregon"))
3558 @result{} (("South Dakota" . "Pierre")
3559 ("New York" . "Albany")
3560 ("Florida" . "Tallahassee"))
3564 @subsection Hash Tables
3565 @tpindex Hash Tables
3567 Hash tables are dictionaries which offer similar functionality as
3568 association lists: They provide a mapping from keys to values. The
3569 difference is that association lists need time linear in the size of
3570 elements when searching for entries, whereas hash tables can normally
3571 search in constant time. The drawback is that hash tables require a
3572 little bit more memory, and that you can not use the normal list
3573 procedures (@pxref{Lists}) for working with them.
3575 Guile provides two types of hashtables. One is an abstract data type
3576 that can only be manipulated with the functions in this section. The
3577 other type is concrete: it uses a normal vector with alists as
3578 elements. The advantage of the abstract hash tables is that they will
3579 be automatically resized when they become too full or too empty.
3582 * Hash Table Examples:: Demonstration of hash table usage.
3583 * Hash Table Reference:: Hash table procedure descriptions.
3587 @node Hash Table Examples
3588 @subsubsection Hash Table Examples
3590 For demonstration purposes, this section gives a few usage examples of
3591 some hash table procedures, together with some explanation what they do.
3593 First we start by creating a new hash table with 31 slots, and
3594 populate it with two key/value pairs.
3597 (define h (make-hash-table 31))
3599 ;; This is an opaque object
3604 ;; We can also use a vector of alists.
3605 (define h (make-vector 7 '()))
3609 #(() () () () () () ())
3611 ;; Inserting into a hash table can be done with hashq-set!
3612 (hashq-set! h 'foo "bar")
3616 (hashq-set! h 'braz "zonk")
3620 ;; Or with hash-create-handle!
3621 (hashq-create-handle! h 'frob #f)
3625 ;; The vector now contains three elements in the alists and the frob
3626 ;; entry is at index (hashq 'frob).
3629 #(((braz . "zonk")) ((foo . "bar")) () () () () ((frob . #f)))
3637 You can get the value for a given key with the procedure
3638 @code{hashq-ref}, but the problem with this procedure is that you
3639 cannot reliably determine whether a key does exists in the table. The
3640 reason is that the procedure returns @code{#f} if the key is not in
3641 the table, but it will return the same value if the key is in the
3642 table and just happens to have the value @code{#f}, as you can see in
3643 the following examples.
3654 (hashq-ref h 'not-there)
3659 Better is to use the procedure @code{hashq-get-handle}, which makes a
3660 distinction between the two cases. Just like @code{assq}, this
3661 procedure returns a key/value-pair on success, and @code{#f} if the
3665 (hashq-get-handle h 'foo)
3669 (hashq-get-handle h 'not-there)
3674 There is no procedure for calculating the number of key/value-pairs in
3675 a hash table, but @code{hash-fold} can be used for doing exactly that.
3678 (hash-fold (lambda (key value seed) (+ 1 seed)) 0 h)
3683 @node Hash Table Reference
3684 @subsubsection Hash Table Reference
3686 @c FIXME: Describe in broad terms what happens for resizing, and what
3687 @c the initial size means for this.
3689 Like the association list functions, the hash table functions come in
3690 several varieties, according to the equality test used for the keys.
3691 Plain @code{hash-} functions use @code{equal?}, @code{hashq-}
3692 functions use @code{eq?}, @code{hashv-} functions use @code{eqv?}, and
3693 the @code{hashx-} functions use an application supplied test.
3695 A single @code{make-hash-table} creates a hash table suitable for use
3696 with any set of functions, but it's imperative that just one set is
3697 then used consistently, or results will be unpredictable.
3699 Hash tables are implemented as a vector indexed by a hash value formed
3700 from the key, with an association list of key/value pairs for each
3701 bucket in case distinct keys hash together. Direct access to the
3702 pairs in those lists is provided by the @code{-handle-} functions.
3703 The abstract kind of hash tables hide the vector in an opaque object
3704 that represents the hash table, while for the concrete kind the vector
3705 @emph{is} the hashtable.
3707 When the number of table entries in an abstract hash table goes above
3708 a threshold, the vector is made larger and the entries are rehashed,
3709 to prevent the bucket lists from becoming too long and slowing down
3710 accesses. When the number of entries goes below a threshold, the
3711 vector is shrunk to save space.
3713 A abstract hash table is created with @code{make-hash-table}. To
3714 create a vector that is suitable as a hash table, use
3715 @code{(make-vector @var{size} '())}, for example.
3717 For the @code{hashx-} ``extended'' routines, an application supplies a
3718 @var{hash} function producing an integer index like @code{hashq} etc
3719 below, and an @var{assoc} alist search function like @code{assq} etc
3720 (@pxref{Retrieving Alist Entries}). Here's an example of such
3721 functions implementing case-insensitive hashing of string keys,
3724 (use-modules (srfi srfi-1)
3727 (define (my-hash str size)
3728 (remainder (string-hash-ci str) size))
3729 (define (my-assoc str alist)
3730 (find (lambda (pair) (string-ci=? str (car pair))) alist))
3732 (define my-table (make-hash-table))
3733 (hashx-set! my-hash my-assoc my-table "foo" 123)
3735 (hashx-ref my-hash my-assoc my-table "FOO")
3739 In a @code{hashx-} @var{hash} function the aim is to spread keys
3740 across the vector, so bucket lists don't become long. But the actual
3741 values are arbitrary as long as they're in the range 0 to
3742 @math{@var{size}-1}. Helpful functions for forming a hash value, in
3743 addition to @code{hashq} etc below, include @code{symbol-hash}
3744 (@pxref{Symbol Keys}), @code{string-hash} and @code{string-hash-ci}
3745 (@pxref{String Comparison}), and @code{char-set-hash}
3746 (@pxref{Character Set Predicates/Comparison}).
3749 @deffn {Scheme Procedure} make-hash-table [size]
3750 Create a new abstract hash table object, with an optional minimum
3753 When @var{size} is given, the table vector will still grow and shrink
3754 automatically, as described above, but with @var{size} as a minimum.
3755 If an application knows roughly how many entries the table will hold
3756 then it can use @var{size} to avoid rehashing when initial entries are
3760 @deffn {Scheme Procedure} hash-table? obj
3761 @deffnx {C Function} scm_hash_table_p (obj)
3762 Return @code{#t} if @var{obj} is a abstract hash table object.
3765 @deffn {Scheme Procedure} hash-clear! table
3766 @deffnx {C Function} scm_hash_clear_x (table)
3767 Remove all items from @var{table} (without triggering a resize).
3770 @deffn {Scheme Procedure} hash-ref table key [dflt]
3771 @deffnx {Scheme Procedure} hashq-ref table key [dflt]
3772 @deffnx {Scheme Procedure} hashv-ref table key [dflt]
3773 @deffnx {Scheme Procedure} hashx-ref hash assoc table key [dflt]
3774 @deffnx {C Function} scm_hash_ref (table, key, dflt)
3775 @deffnx {C Function} scm_hashq_ref (table, key, dflt)
3776 @deffnx {C Function} scm_hashv_ref (table, key, dflt)
3777 @deffnx {C Function} scm_hashx_ref (hash, assoc, table, key, dflt)
3778 Lookup @var{key} in the given hash @var{table}, and return the
3779 associated value. If @var{key} is not found, return @var{dflt}, or
3780 @code{#f} if @var{dflt} is not given.
3783 @deffn {Scheme Procedure} hash-set! table key val
3784 @deffnx {Scheme Procedure} hashq-set! table key val
3785 @deffnx {Scheme Procedure} hashv-set! table key val
3786 @deffnx {Scheme Procedure} hashx-set! hash assoc table key val
3787 @deffnx {C Function} scm_hash_set_x (table, key, val)
3788 @deffnx {C Function} scm_hashq_set_x (table, key, val)
3789 @deffnx {C Function} scm_hashv_set_x (table, key, val)
3790 @deffnx {C Function} scm_hashx_set_x (hash, assoc, table, key, val)
3791 Associate @var{val} with @var{key} in the given hash @var{table}. If
3792 @var{key} is already present then it's associated value is changed.
3793 If it's not present then a new entry is created.
3796 @deffn {Scheme Procedure} hash-remove! table key
3797 @deffnx {Scheme Procedure} hashq-remove! table key
3798 @deffnx {Scheme Procedure} hashv-remove! table key
3799 @deffnx {Scheme Procedure} hashx-remove! hash assoc table key
3800 @deffnx {C Function} scm_hash_remove_x (table, key)
3801 @deffnx {C Function} scm_hashq_remove_x (table, key)
3802 @deffnx {C Function} scm_hashv_remove_x (table, key)
3803 @deffnx {C Function} scm_hashx_remove_x (hash, assoc, table, key)
3804 Remove any association for @var{key} in the given hash @var{table}.
3805 If @var{key} is not in @var{table} then nothing is done.
3808 @deffn {Scheme Procedure} hash key size
3809 @deffnx {Scheme Procedure} hashq key size
3810 @deffnx {Scheme Procedure} hashv key size
3811 @deffnx {C Function} scm_hash (key, size)
3812 @deffnx {C Function} scm_hashq (key, size)
3813 @deffnx {C Function} scm_hashv (key, size)
3814 Return a hash value for @var{key}. This is a number in the range
3815 @math{0} to @math{@var{size}-1}, which is suitable for use in a hash
3816 table of the given @var{size}.
3818 Note that @code{hashq} and @code{hashv} may use internal addresses of
3819 objects, so if an object is garbage collected and re-created it can
3820 have a different hash value, even when the two are notionally
3821 @code{eq?}. For instance with symbols,
3824 (hashq 'something 123) @result{} 19
3826 (hashq 'something 123) @result{} 62
3829 In normal use this is not a problem, since an object entered into a
3830 hash table won't be garbage collected until removed. It's only if
3831 hashing calculations are somehow separated from normal references that
3832 its lifetime needs to be considered.
3835 @deffn {Scheme Procedure} hash-get-handle table key
3836 @deffnx {Scheme Procedure} hashq-get-handle table key
3837 @deffnx {Scheme Procedure} hashv-get-handle table key
3838 @deffnx {Scheme Procedure} hashx-get-handle hash assoc table key
3839 @deffnx {C Function} scm_hash_get_handle (table, key)
3840 @deffnx {C Function} scm_hashq_get_handle (table, key)
3841 @deffnx {C Function} scm_hashv_get_handle (table, key)
3842 @deffnx {C Function} scm_hashx_get_handle (hash, assoc, table, key)
3843 Return the @code{(@var{key} . @var{value})} pair for @var{key} in the
3844 given hash @var{table}, or @code{#f} if @var{key} is not in
3848 @deffn {Scheme Procedure} hash-create-handle! table key init
3849 @deffnx {Scheme Procedure} hashq-create-handle! table key init
3850 @deffnx {Scheme Procedure} hashv-create-handle! table key init
3851 @deffnx {Scheme Procedure} hashx-create-handle! hash assoc table key init
3852 @deffnx {C Function} scm_hash_create_handle_x (table, key, init)
3853 @deffnx {C Function} scm_hashq_create_handle_x (table, key, init)
3854 @deffnx {C Function} scm_hashv_create_handle_x (table, key, init)
3855 @deffnx {C Function} scm_hashx_create_handle_x (hash, assoc, table, key, init)
3856 Return the @code{(@var{key} . @var{value})} pair for @var{key} in the
3857 given hash @var{table}. If @var{key} is not in @var{table} then
3858 create an entry for it with @var{init} as the value, and return that
3862 @deffn {Scheme Procedure} hash-map->list proc table
3863 @deffnx {Scheme Procedure} hash-for-each proc table
3864 @deffnx {C Function} scm_hash_map_to_list (proc, table)
3865 @deffnx {C Function} scm_hash_for_each (proc, table)
3866 Apply @var{proc} to the entries in the given hash @var{table}. Each
3867 call is @code{(@var{proc} @var{key} @var{value})}. @code{hash-map->list}
3868 returns a list of the results from these calls, @code{hash-for-each}
3869 discards the results and returns an unspecified value.
3871 Calls are made over the table entries in an unspecified order, and for
3872 @code{hash-map->list} the order of the values in the returned list is
3873 unspecified. Results will be unpredictable if @var{table} is modified
3876 For example the following returns a new alist comprising all the
3877 entries from @code{mytable}, in no particular order.
3880 (hash-map->list cons mytable)
3884 @deffn {Scheme Procedure} hash-for-each-handle proc table
3885 @deffnx {C Function} scm_hash_for_each_handle (proc, table)
3886 Apply @var{proc} to the entries in the given hash @var{table}. Each
3887 call is @code{(@var{proc} @var{handle})}, where @var{handle} is a
3888 @code{(@var{key} . @var{value})} pair. Return an unspecified value.
3890 @code{hash-for-each-handle} differs from @code{hash-for-each} only in
3891 the argument list of @var{proc}.
3894 @deffn {Scheme Procedure} hash-fold proc init table
3895 @deffnx {C Function} scm_hash_fold (proc, init, table)
3896 Accumulate a result by applying @var{proc} to the elements of the
3897 given hash @var{table}. Each call is @code{(@var{proc} @var{key}
3898 @var{value} @var{prior-result})}, where @var{key} and @var{value} are
3899 from the @var{table} and @var{prior-result} is the return from the
3900 previous @var{proc} call. For the first call, @var{prior-result} is
3901 the given @var{init} value.
3903 Calls are made over the table entries in an unspecified order.
3904 Results will be unpredictable if @var{table} is modified while
3905 @code{hash-fold} is running.
3907 For example, the following returns a count of how many keys in
3908 @code{mytable} are strings.
3911 (hash-fold (lambda (key value prior)
3912 (if (string? key) (1+ prior) prior))
3919 @c TeX-master: "guile.texi"