1 /* Copyright (C) 1995,1996,1997,2000,2001,2003,2004,2008,2009,2010,2011
2 * Free Software Foundation, Inc.
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public License
6 * as published by the Free Software Foundation; either version 3 of
7 * the License, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
26 #include "libguile/_scm.h"
27 #include "libguile/eq.h"
29 #include "libguile/validate.h"
30 #include "libguile/list.h"
31 #include "libguile/eval.h"
38 #define SCM_I_CONS(cell, x, y) \
40 cell = scm_cell ((scm_t_bits)x, (scm_t_bits)y); \
47 SCM_I_CONS (c1
, e1
, SCM_EOL
);
52 scm_list_2 (SCM e1
, SCM e2
)
55 SCM_I_CONS (c2
, e2
, SCM_EOL
);
56 SCM_I_CONS (c1
, e1
, c2
);
61 scm_list_3 (SCM e1
, SCM e2
, SCM e3
)
64 SCM_I_CONS (c3
, e3
, SCM_EOL
);
65 SCM_I_CONS (c2
, e2
, c3
);
66 SCM_I_CONS (c1
, e1
, c2
);
71 scm_list_4 (SCM e1
, SCM e2
, SCM e3
, SCM e4
)
73 return scm_cons2 (e1
, e2
, scm_list_2 (e3
, e4
));
77 scm_list_5 (SCM e1
, SCM e2
, SCM e3
, SCM e4
, SCM e5
)
79 return scm_cons2 (e1
, e2
, scm_list_3 (e3
, e4
, e5
));
83 scm_list_n (SCM elt
, ...)
90 while (! SCM_UNBNDP (elt
))
92 #if (SCM_DEBUG_CELL_ACCESSES == 1)
94 SCM_VALIDATE_CELL(elt
, 0);
96 *pos
= scm_cons (elt
, SCM_EOL
);
97 pos
= SCM_CDRLOC (*pos
);
98 elt
= va_arg (foo
, SCM
);
105 SCM_DEFINE (scm_make_list
, "make-list", 1, 1, 0,
107 "Create a list containing of @var{n} elements, where each\n"
108 "element is initialized to @var{init}. @var{init} defaults to\n"
109 "the empty list @code{()} if not given.")
110 #define FUNC_NAME s_scm_make_list
112 unsigned nn
= scm_to_uint (n
);
116 if (SCM_UNBNDP (init
))
119 for (i
= 0; i
< nn
; i
++)
120 ret
= scm_cons (init
, ret
);
126 SCM_DEFINE (scm_cons_star
, "cons*", 1, 0, 1,
128 "Like @code{list}, but the last arg provides the tail of the\n"
129 "constructed list, returning @code{(cons @var{arg1} (cons\n"
130 "@var{arg2} (cons @dots{} @var{argn})))}. Requires at least one\n"
131 "argument. If given one argument, that argument is returned as\n"
132 "result. This function is called @code{list*} in some other\n"
133 "Schemes and in Common LISP.")
134 #define FUNC_NAME s_scm_cons_star
139 SCM_VALIDATE_REST_ARGUMENT (rest
);
141 for ( ; scm_is_pair (rest
); rest
= SCM_CDR (rest
))
143 *p
= scm_cons (arg
, SCM_EOL
);
145 arg
= SCM_CAR (rest
);
155 /* general questions about lists --- null?, list?, length, etc. */
157 SCM_DEFINE (scm_null_p
, "null?", 1, 0, 0,
159 "Return @code{#t} iff @var{x} is the empty list, else @code{#f}.")
160 #define FUNC_NAME s_scm_null_p
162 return scm_from_bool (SCM_NULL_OR_NIL_P (x
));
167 SCM_DEFINE (scm_list_p
, "list?", 1, 0, 0,
169 "Return @code{#t} iff @var{x} is a proper list, else @code{#f}.")
170 #define FUNC_NAME s_scm_list_p
172 return scm_from_bool (scm_ilength (x
) >= 0);
177 /* Return the length of SX, or -1 if it's not a proper list.
178 This uses the "tortoise and hare" algorithm to detect "infinitely
179 long" lists (i.e. lists with cycles in their cdrs), and returns -1
180 if it does find one. */
189 if (SCM_NULL_OR_NIL_P(hare
)) return i
;
190 if (!scm_is_pair (hare
)) return -1;
191 hare
= SCM_CDR(hare
);
193 if (SCM_NULL_OR_NIL_P(hare
)) return i
;
194 if (!scm_is_pair (hare
)) return -1;
195 hare
= SCM_CDR(hare
);
197 /* For every two steps the hare takes, the tortoise takes one. */
198 tortoise
= SCM_CDR(tortoise
);
200 while (!scm_is_eq (hare
, tortoise
));
202 /* If the tortoise ever catches the hare, then the list must contain
208 SCM_DEFINE (scm_length
, "length", 1, 0, 0,
210 "Return the number of elements in list @var{lst}.")
211 #define FUNC_NAME s_scm_length
214 SCM_VALIDATE_LIST_COPYLEN (1, lst
, i
);
215 return scm_from_long (i
);
221 /* appending lists */
223 SCM_DEFINE (scm_append
, "append", 0, 0, 1,
225 "Return a list consisting of the elements the lists passed as\n"
228 "(append '(x) '(y)) @result{} (x y)\n"
229 "(append '(a) '(b c d)) @result{} (a b c d)\n"
230 "(append '(a (b)) '((c))) @result{} (a (b) (c))\n"
232 "The resulting list is always newly allocated, except that it\n"
233 "shares structure with the last list argument. The last\n"
234 "argument may actually be any object; an improper list results\n"
235 "if the last argument is not a proper list.\n"
237 "(append '(a b) '(c . d)) @result{} (a b c . d)\n"
238 "(append '() 'a) @result{} a\n"
240 #define FUNC_NAME s_scm_append
242 SCM_VALIDATE_REST_ARGUMENT (args
);
243 if (scm_is_null (args
)) {
248 SCM arg
= SCM_CAR (args
);
250 args
= SCM_CDR (args
);
251 while (!scm_is_null (args
)) {
252 while (scm_is_pair (arg
)) {
253 *lloc
= scm_cons (SCM_CAR (arg
), SCM_EOL
);
254 lloc
= SCM_CDRLOC (*lloc
);
257 SCM_VALIDATE_NULL_OR_NIL (argnum
, arg
);
258 arg
= SCM_CAR (args
);
259 args
= SCM_CDR (args
);
269 SCM_DEFINE (scm_append_x
, "append!", 0, 0, 1,
271 "A destructive version of @code{append} (@pxref{Pairs and\n"
272 "Lists,,,r5rs, The Revised^5 Report on Scheme}). The cdr field\n"
273 "of each list's final pair is changed to point to the head of\n"
274 "the next list, so no consing is performed. Return\n"
276 #define FUNC_NAME s_scm_append_x
279 SCM_VALIDATE_REST_ARGUMENT (lists
);
281 if (scm_is_null (lists
))
287 SCM arg
= SCM_CAR (lists
);
290 lists
= SCM_CDR (lists
);
291 if (scm_is_null (lists
))
294 if (!SCM_NULL_OR_NIL_P (arg
))
296 SCM_VALIDATE_CONS (SCM_ARG1
, arg
);
297 loc
= SCM_CDRLOC (scm_last_pair (arg
));
304 SCM_DEFINE (scm_last_pair
, "last-pair", 1, 0, 0,
306 "Return the last pair in @var{lst}, signalling an error if\n"
307 "@var{lst} is circular.")
308 #define FUNC_NAME s_scm_last_pair
313 if (SCM_NULL_OR_NIL_P (lst
))
316 SCM_VALIDATE_CONS (SCM_ARG1
, lst
);
318 SCM ahead
= SCM_CDR(hare
);
319 if (!scm_is_pair (ahead
)) return hare
;
321 ahead
= SCM_CDR(hare
);
322 if (!scm_is_pair (ahead
)) return hare
;
324 tortoise
= SCM_CDR(tortoise
);
326 while (!scm_is_eq (hare
, tortoise
));
327 SCM_MISC_ERROR ("Circular structure in position 1: ~S", scm_list_1 (lst
));
332 /* reversing lists */
334 SCM_DEFINE (scm_reverse
, "reverse", 1, 0, 0,
336 "Return a new list that contains the elements of @var{lst} but\n"
338 #define FUNC_NAME s_scm_reverse
340 SCM result
= SCM_EOL
;
345 if (SCM_NULL_OR_NIL_P(hare
)) return result
;
346 SCM_ASSERT(scm_is_pair(hare
), lst
, 1, FUNC_NAME
);
347 result
= scm_cons (SCM_CAR (hare
), result
);
348 hare
= SCM_CDR (hare
);
349 if (SCM_NULL_OR_NIL_P(hare
)) return result
;
350 SCM_ASSERT(scm_is_pair(hare
), lst
, 1, FUNC_NAME
);
351 result
= scm_cons (SCM_CAR (hare
), result
);
352 hare
= SCM_CDR (hare
);
353 tortoise
= SCM_CDR (tortoise
);
355 while (!scm_is_eq (hare
, tortoise
));
356 SCM_MISC_ERROR ("Circular structure in position 1: ~S", scm_list_1 (lst
));
360 SCM_DEFINE (scm_reverse_x
, "reverse!", 1, 1, 0,
361 (SCM lst
, SCM new_tail
),
362 "A destructive version of @code{reverse} (@pxref{Pairs and Lists,,,r5rs,\n"
363 "The Revised^5 Report on Scheme}). The cdr of each cell in @var{lst} is\n"
364 "modified to point to the previous list element. Return the\n"
366 "Caveat: because the list is modified in place, the tail of the original\n"
367 "list now becomes its head, and the head of the original list now becomes\n"
368 "the tail. Therefore, the @var{lst} symbol to which the head of the\n"
369 "original list was bound now points to the tail. To ensure that the head\n"
370 "of the modified list is not lost, it is wise to save the return value of\n"
372 #define FUNC_NAME s_scm_reverse_x
374 SCM_VALIDATE_LIST (1, lst
);
375 if (SCM_UNBNDP (new_tail
))
378 SCM_VALIDATE_LIST (2, new_tail
);
380 while (!SCM_NULL_OR_NIL_P (lst
))
382 SCM old_tail
= SCM_CDR (lst
);
383 SCM_SETCDR (lst
, new_tail
);
393 /* indexing lists by element number */
395 SCM_DEFINE (scm_list_ref
, "list-ref", 2, 0, 0,
397 "Return the @var{k}th element from @var{list}.")
398 #define FUNC_NAME s_scm_list_ref
402 i
= scm_to_ulong (k
);
403 while (scm_is_pair (lst
)) {
405 return SCM_CAR (lst
);
411 if (SCM_NULL_OR_NIL_P (lst
))
412 SCM_OUT_OF_RANGE (2, k
);
414 SCM_WRONG_TYPE_ARG (1, list
);
419 SCM_DEFINE (scm_list_set_x
, "list-set!", 3, 0, 0,
420 (SCM list
, SCM k
, SCM val
),
421 "Set the @var{k}th element of @var{list} to @var{val}.")
422 #define FUNC_NAME s_scm_list_set_x
425 unsigned long int i
= scm_to_ulong (k
);
426 while (scm_is_pair (lst
)) {
428 SCM_SETCAR (lst
, val
);
435 if (SCM_NULL_OR_NIL_P (lst
))
436 SCM_OUT_OF_RANGE (2, k
);
438 SCM_WRONG_TYPE_ARG (1, list
);
443 SCM_REGISTER_PROC(s_list_cdr_ref
, "list-cdr-ref", 2, 0, 0, scm_list_tail
);
445 SCM_DEFINE (scm_list_tail
, "list-tail", 2, 0, 0,
447 "@deffnx {Scheme Procedure} list-cdr-ref lst k\n"
448 "Return the \"tail\" of @var{lst} beginning with its @var{k}th element.\n"
449 "The first element of the list is considered to be element 0.\n\n"
450 "@code{list-tail} and @code{list-cdr-ref} are identical. It may help to\n"
451 "think of @code{list-cdr-ref} as accessing the @var{k}th cdr of the list,\n"
452 "or returning the results of cdring @var{k} times down @var{lst}.")
453 #define FUNC_NAME s_scm_list_tail
455 size_t i
= scm_to_size_t (k
);
457 SCM_VALIDATE_CONS (1, lst
);
465 SCM_DEFINE (scm_list_cdr_set_x
, "list-cdr-set!", 3, 0, 0,
466 (SCM list
, SCM k
, SCM val
),
467 "Set the @var{k}th cdr of @var{list} to @var{val}.")
468 #define FUNC_NAME s_scm_list_cdr_set_x
471 size_t i
= scm_to_size_t (k
);
472 while (scm_is_pair (lst
)) {
474 SCM_SETCDR (lst
, val
);
481 if (SCM_NULL_OR_NIL_P (lst
))
482 SCM_OUT_OF_RANGE (2, k
);
484 SCM_WRONG_TYPE_ARG (1, list
);
490 /* copying lists, perhaps partially */
492 SCM_DEFINE (scm_list_head
, "list-head", 2, 0, 0,
494 "Copy the first @var{k} elements from @var{lst} into a new list, and\n"
496 #define FUNC_NAME s_scm_list_head
500 size_t i
= scm_to_size_t (k
);
506 SCM_VALIDATE_CONS (1, lst
);
507 *pos
= scm_cons (SCM_CAR (lst
), SCM_EOL
);
508 pos
= SCM_CDRLOC (*pos
);
516 /* Copy a list which is known to be finite. The last pair may or may not have
517 * a '() in its cdr. That is, improper lists are accepted. */
519 scm_i_finite_list_copy (SCM list
)
521 if (!scm_is_pair (list
))
528 const SCM result
= tail
= scm_list_1 (SCM_CAR (list
));
529 list
= SCM_CDR (list
);
530 while (scm_is_pair (list
))
532 const SCM new_tail
= scm_list_1 (SCM_CAR (list
));
533 SCM_SETCDR (tail
, new_tail
);
535 list
= SCM_CDR (list
);
537 SCM_SETCDR (tail
, list
);
544 SCM_DEFINE (scm_list_copy
, "list-copy", 1, 0, 0,
546 "Return a (newly-created) copy of @var{lst}.")
547 #define FUNC_NAME s_scm_list_copy
553 SCM_VALIDATE_LIST (1, lst
);
559 while (scm_is_pair (from_here
))
562 c
= scm_cons (SCM_CAR (from_here
), SCM_CDR (from_here
));
564 fill_here
= SCM_CDRLOC (c
);
565 from_here
= SCM_CDR (from_here
);
572 SCM_PROC (s_list
, "list", 0, 0, 1, scm_list_copy
);
573 SCM_SNARF_DOCS (primitive
, scm_list_copy
, "list", (SCM objs
), 0, 0, 1,
574 "Return a list containing @var{objs}, the arguments to\n"
577 /* This used to be the code for "list", but it's wrong when used via apply
578 (it should copy the list). It seems pretty unlikely anyone would have
579 been using this from C code, since it's a no-op, but keep it for strict
580 binary compatibility. */
589 /* membership tests (memq, memv, etc.) */
591 /* The function scm_c_memq returns the first sublist of list whose car is
592 * 'eq?' obj, where the sublists of list are the non-empty lists returned by
593 * (list-tail list k) for k less than the length of list. If obj does not
594 * occur in list, then #f (not the empty list) is returned.
595 * List must be a proper list, otherwise scm_c_memq may crash or loop
599 scm_c_memq (SCM obj
, SCM list
)
601 for (; !SCM_NULL_OR_NIL_P (list
); list
= SCM_CDR (list
))
603 if (scm_is_eq (SCM_CAR (list
), obj
))
610 SCM_DEFINE (scm_memq
, "memq", 2, 0, 0,
612 "Return the first sublist of @var{lst} whose car is @code{eq?}\n"
613 "to @var{x} where the sublists of @var{lst} are the non-empty\n"
614 "lists returned by @code{(list-tail @var{lst} @var{k})} for\n"
615 "@var{k} less than the length of @var{lst}. If @var{x} does not\n"
616 "occur in @var{lst}, then @code{#f} (not the empty list) is\n"
618 #define FUNC_NAME s_scm_memq
620 SCM hare
= lst
, tortoise
= lst
;
622 while (scm_is_pair (hare
))
624 if (scm_is_eq (SCM_CAR (hare
), x
))
627 hare
= SCM_CDR (hare
);
629 if (!scm_is_pair (hare
))
632 if (scm_is_eq (SCM_CAR (hare
), x
))
635 hare
= SCM_CDR (hare
);
637 tortoise
= SCM_CDR (tortoise
);
638 if (SCM_UNLIKELY (scm_is_eq (hare
, tortoise
)))
642 if (SCM_LIKELY (scm_is_null (hare
)))
645 scm_wrong_type_arg_msg (FUNC_NAME
, 2, lst
, "list");
650 SCM_DEFINE (scm_memv
, "memv", 2, 0, 0,
652 "Return the first sublist of @var{lst} whose car is @code{eqv?}\n"
653 "to @var{x} where the sublists of @var{lst} are the non-empty\n"
654 "lists returned by @code{(list-tail @var{lst} @var{k})} for\n"
655 "@var{k} less than the length of @var{lst}. If @var{x} does not\n"
656 "occur in @var{lst}, then @code{#f} (not the empty list) is\n"
658 #define FUNC_NAME s_scm_memv
660 SCM hare
= lst
, tortoise
= lst
;
662 while (scm_is_pair (hare
))
664 if (scm_is_true (scm_eqv_p (SCM_CAR (hare
), x
)))
667 hare
= SCM_CDR (hare
);
669 if (!scm_is_pair (hare
))
672 if (scm_is_true (scm_eqv_p (SCM_CAR (hare
), x
)))
675 hare
= SCM_CDR (hare
);
677 tortoise
= SCM_CDR (tortoise
);
678 if (SCM_UNLIKELY (scm_is_eq (hare
, tortoise
)))
682 if (SCM_LIKELY (scm_is_null (hare
)))
685 scm_wrong_type_arg_msg (FUNC_NAME
, 2, lst
, "list");
690 SCM_DEFINE (scm_member
, "member", 2, 0, 0,
692 "Return the first sublist of @var{lst} whose car is\n"
693 "@code{equal?} to @var{x} where the sublists of @var{lst} are\n"
694 "the non-empty lists returned by @code{(list-tail @var{lst}\n"
695 "@var{k})} for @var{k} less than the length of @var{lst}. If\n"
696 "@var{x} does not occur in @var{lst}, then @code{#f} (not the\n"
697 "empty list) is returned.")
698 #define FUNC_NAME s_scm_member
700 SCM_VALIDATE_LIST (2, lst
);
701 for (; !SCM_NULL_OR_NIL_P (lst
); lst
= SCM_CDR (lst
))
703 if (! scm_is_false (scm_equal_p (SCM_CAR (lst
), x
)))
711 /* deleting elements from a list (delq, etc.) */
713 SCM_DEFINE (scm_delq_x
, "delq!", 2, 0, 0,
715 "@deffnx {Scheme Procedure} delv! item lst\n"
716 "@deffnx {Scheme Procedure} delete! item lst\n"
717 "These procedures are destructive versions of @code{delq}, @code{delv}\n"
718 "and @code{delete}: they modify the existing @var{lst}\n"
719 "rather than creating a new list. Caveat evaluator: Like other\n"
720 "destructive list functions, these functions cannot modify the binding of\n"
721 "@var{lst}, and so cannot be used to delete the first element of\n"
722 "@var{lst} destructively.")
723 #define FUNC_NAME s_scm_delq_x
728 for (prev
= &lst
, walk
= lst
;
730 walk
= SCM_CDR (walk
))
732 if (scm_is_eq (SCM_CAR (walk
), item
))
733 *prev
= SCM_CDR (walk
);
735 prev
= SCM_CDRLOC (walk
);
743 SCM_DEFINE (scm_delv_x
, "delv!", 2, 0, 0,
745 "Destructively remove all elements from @var{lst} that are\n"
746 "@code{eqv?} to @var{item}.")
747 #define FUNC_NAME s_scm_delv_x
752 for (prev
= &lst
, walk
= lst
;
754 walk
= SCM_CDR (walk
))
756 if (! scm_is_false (scm_eqv_p (SCM_CAR (walk
), item
)))
757 *prev
= SCM_CDR (walk
);
759 prev
= SCM_CDRLOC (walk
);
768 SCM_DEFINE (scm_delete_x
, "delete!", 2, 0, 0,
770 "Destructively remove all elements from @var{lst} that are\n"
771 "@code{equal?} to @var{item}.")
772 #define FUNC_NAME s_scm_delete_x
777 for (prev
= &lst
, walk
= lst
;
779 walk
= SCM_CDR (walk
))
781 if (! scm_is_false (scm_equal_p (SCM_CAR (walk
), item
)))
782 *prev
= SCM_CDR (walk
);
784 prev
= SCM_CDRLOC (walk
);
795 SCM_DEFINE (scm_delq
, "delq", 2, 0, 0,
797 "Return a newly-created copy of @var{lst} with elements\n"
798 "@code{eq?} to @var{item} removed. This procedure mirrors\n"
799 "@code{memq}: @code{delq} compares elements of @var{lst} against\n"
800 "@var{item} with @code{eq?}.")
801 #define FUNC_NAME s_scm_delq
803 SCM copy
= scm_list_copy (lst
);
804 return scm_delq_x (item
, copy
);
808 SCM_DEFINE (scm_delv
, "delv", 2, 0, 0,
810 "Return a newly-created copy of @var{lst} with elements\n"
811 "@code{eqv?} to @var{item} removed. This procedure mirrors\n"
812 "@code{memv}: @code{delv} compares elements of @var{lst} against\n"
813 "@var{item} with @code{eqv?}.")
814 #define FUNC_NAME s_scm_delv
816 SCM copy
= scm_list_copy (lst
);
817 return scm_delv_x (item
, copy
);
821 SCM_DEFINE (scm_delete
, "delete", 2, 0, 0,
823 "Return a newly-created copy of @var{lst} with elements\n"
824 "@code{equal?} to @var{item} removed. This procedure mirrors\n"
825 "@code{member}: @code{delete} compares elements of @var{lst}\n"
826 "against @var{item} with @code{equal?}.")
827 #define FUNC_NAME s_scm_delete
829 SCM copy
= scm_list_copy (lst
);
830 return scm_delete_x (item
, copy
);
835 SCM_DEFINE (scm_delq1_x
, "delq1!", 2, 0, 0,
837 "Like @code{delq!}, but only deletes the first occurrence of\n"
838 "@var{item} from @var{lst}. Tests for equality using\n"
839 "@code{eq?}. See also @code{delv1!} and @code{delete1!}.")
840 #define FUNC_NAME s_scm_delq1_x
845 for (prev
= &lst
, walk
= lst
;
847 walk
= SCM_CDR (walk
))
849 if (scm_is_eq (SCM_CAR (walk
), item
))
851 *prev
= SCM_CDR (walk
);
855 prev
= SCM_CDRLOC (walk
);
863 SCM_DEFINE (scm_delv1_x
, "delv1!", 2, 0, 0,
865 "Like @code{delv!}, but only deletes the first occurrence of\n"
866 "@var{item} from @var{lst}. Tests for equality using\n"
867 "@code{eqv?}. See also @code{delq1!} and @code{delete1!}.")
868 #define FUNC_NAME s_scm_delv1_x
873 for (prev
= &lst
, walk
= lst
;
875 walk
= SCM_CDR (walk
))
877 if (! scm_is_false (scm_eqv_p (SCM_CAR (walk
), item
)))
879 *prev
= SCM_CDR (walk
);
883 prev
= SCM_CDRLOC (walk
);
891 SCM_DEFINE (scm_delete1_x
, "delete1!", 2, 0, 0,
893 "Like @code{delete!}, but only deletes the first occurrence of\n"
894 "@var{item} from @var{lst}. Tests for equality using\n"
895 "@code{equal?}. See also @code{delq1!} and @code{delv1!}.")
896 #define FUNC_NAME s_scm_delete1_x
901 for (prev
= &lst
, walk
= lst
;
903 walk
= SCM_CDR (walk
))
905 if (! scm_is_false (scm_equal_p (SCM_CAR (walk
), item
)))
907 *prev
= SCM_CDR (walk
);
911 prev
= SCM_CDRLOC (walk
);
918 SCM_DEFINE (scm_filter
, "filter", 2, 0, 0,
919 (SCM pred
, SCM list
),
920 "Return all the elements of 2nd arg @var{list} that satisfy predicate @var{pred}.\n"
921 "The list is not disordered -- elements that appear in the result list occur\n"
922 "in the same order as they occur in the argument list. The returned list may\n"
923 "share a common tail with the argument list. The dynamic order in which the\n"
924 "various applications of pred are made is not specified.\n\n"
926 "(filter even? '(0 7 8 8 43 -4)) => (0 8 8 -4)\n"
928 #define FUNC_NAME s_scm_filter
933 SCM_ASSERT (scm_is_true (scm_procedure_p (pred
)), pred
, 1, FUNC_NAME
);
934 SCM_VALIDATE_LIST (2, list
);
936 for (prev
= &res
, walk
= list
;
938 walk
= SCM_CDR (walk
))
940 if (scm_is_true (scm_call_1 (pred
, SCM_CAR (walk
))))
942 *prev
= scm_cons (SCM_CAR (walk
), SCM_EOL
);
943 prev
= SCM_CDRLOC (*prev
);
951 SCM_DEFINE (scm_filter_x
, "filter!", 2, 0, 0,
952 (SCM pred
, SCM list
),
953 "Linear-update variant of @code{filter}.")
954 #define FUNC_NAME s_scm_filter_x
958 SCM_ASSERT (scm_is_true (scm_procedure_p (pred
)), pred
, 1, FUNC_NAME
);
959 SCM_VALIDATE_LIST (2, list
);
961 for (prev
= &list
, walk
= list
;
963 walk
= SCM_CDR (walk
))
965 if (scm_is_true (scm_call_1 (pred
, SCM_CAR (walk
))))
966 prev
= SCM_CDRLOC (walk
);
968 *prev
= SCM_CDR (walk
);
979 #include "libguile/list.x"