1 /* Copyright (C) 1999,2000,2001,2002, 2004 Free Software Foundation, Inc.
2 * This library is free software; you can redistribute it and/or
3 * modify it under the terms of the GNU Lesser General Public
4 * License as published by the Free Software Foundation; either
5 * version 2.1 of the License, or (at your option) any later version.
7 * This library is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
10 * Lesser General Public License for more details.
12 * You should have received a copy of the GNU Lesser General Public
13 * License along with this library; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19 /* Written in December 1998 by Roland Orre <orre@nada.kth.se>
20 * This implements the same sort interface as slib/sort.scm
21 * for lists and vectors where slib defines:
22 * sorted?, merge, merge!, sort, sort!
23 * For scsh compatibility sort-list and sort-list! are also defined.
24 * In cases where a stable-sort is required use stable-sort or
25 * stable-sort!. An additional feature is
26 * (restricted-vector-sort! vector less? startpos endpos)
27 * which allows you to sort part of a vector.
28 * Thanks to Aubrey Jaffer for the slib/sort.scm library.
29 * Thanks to Richard A. O'Keefe (based on Prolog code by D.H.D.Warren)
30 * for the merge sort inspiration.
31 * Thanks to Douglas C. Schmidt (schmidt@ics.uci.edu) for the
35 #include "libguile/_scm.h"
36 #include "libguile/eval.h"
37 #include "libguile/unif.h"
38 #include "libguile/ramap.h"
39 #include "libguile/feature.h"
40 #include "libguile/vectors.h"
41 #include "libguile/lang.h"
42 #include "libguile/async.h"
44 #include "libguile/validate.h"
45 #include "libguile/sort.h"
47 /* The routine quicksort was extracted from the GNU C Library qsort.c
48 written by Douglas C. Schmidt (schmidt@ics.uci.edu)
49 and adapted to guile by adding an extra pointer less
50 to quicksort by Roland Orre <orre@nada.kth.se>.
52 The reason to do this instead of using the library function qsort
53 was to avoid dependency of the ANSI-C extensions for local functions
54 and also to avoid obscure pool based solutions.
56 This sorting routine is not much more efficient than the stable
57 version but doesn't consume extra memory.
60 #define SWAP(a, b) do { const SCM _tmp = a; a = b; b = _tmp; } while (0)
63 /* Order size using quicksort. This implementation incorporates
64 four optimizations discussed in Sedgewick:
66 1. Non-recursive, using an explicit stack of pointer that store the next
67 array partition to sort. To save time, this maximum amount of space
68 required to store an array of MAX_SIZE_T is allocated on the stack.
69 Assuming a bit width of 32 bits for size_t, this needs only
70 32 * sizeof (stack_node) == 128 bytes. Pretty cheap, actually.
72 2. Chose the pivot element using a median-of-three decision tree. This
73 reduces the probability of selecting a bad pivot value and eliminates
74 certain extraneous comparisons.
76 3. Only quicksorts NR_ELEMS / MAX_THRESH partitions, leaving insertion sort
77 to order the MAX_THRESH items within each partition. This is a big win,
78 since insertion sort is faster for small, mostly sorted array segments.
80 4. The larger of the two sub-partitions is always pushed onto the
81 stack first, with the algorithm then concentrating on the
82 smaller partition. This *guarantees* no more than log (n)
83 stack size is needed (actually O(1) in this case)! */
86 /* Discontinue quicksort algorithm when partition gets below this size.
87 * This particular magic number was chosen to work best on a Sun 4/260. */
91 /* Inline stack abstraction: The stack size for quicksorting at most as many
92 * elements as can be given by a value of type size_t is, as described above,
93 * log (MAX_SIZE_T), which is the number of bits of size_t. More accurately,
94 * we would only need ceil (log (MAX_SIZE_T / MAX_THRESH)), but this is
97 /* Stack node declarations used to store unfulfilled partition obligations. */
103 #define STACK_SIZE (8 * sizeof (size_t)) /* assume 8 bit char */
104 #define PUSH(low, high) ((void) ((top->lo = (low)), (top->hi = (high)), ++top))
105 #define POP(low, high) ((void) (--top, (low = top->lo), (high = top->hi)))
106 #define STACK_NOT_EMPTY (stack < top)
110 quicksort (SCM
*const base_ptr
, size_t nr_elems
, scm_t_trampoline_2 cmp
, SCM less
)
112 static const char s_buggy_less
[] = "buggy less predicate used when sorting";
115 /* Avoid lossage with unsigned arithmetic below. */
118 if (nr_elems
> MAX_THRESH
)
121 size_t hi
= nr_elems
- 1;
123 stack_node stack
[STACK_SIZE
];
124 stack_node
*top
= stack
+ 1;
126 while (STACK_NOT_EMPTY
)
130 size_t mid
= lo
+ (hi
- lo
) / 2;
133 /* Select median value from among LO, MID, and HI. Rearrange
134 LO and HI so the three values are sorted. This lowers the
135 probability of picking a pathological pivot value and
136 skips a comparison for both the left and right. */
140 if (scm_is_true ((*cmp
) (less
, base_ptr
[mid
], base_ptr
[lo
])))
141 SWAP (base_ptr
[mid
], base_ptr
[lo
]);
142 if (scm_is_true ((*cmp
) (less
, base_ptr
[hi
], base_ptr
[mid
])))
143 SWAP (base_ptr
[mid
], base_ptr
[hi
]);
146 if (scm_is_true ((*cmp
) (less
, base_ptr
[mid
], base_ptr
[lo
])))
147 SWAP (base_ptr
[mid
], base_ptr
[lo
]);
150 pivot
= base_ptr
[mid
];
154 /* Here's the famous ``collapse the walls'' section of quicksort.
155 Gotta like those tight inner loops! They are the main reason
156 that this algorithm runs much faster than others. */
159 while (scm_is_true ((*cmp
) (less
, base_ptr
[left
], pivot
)))
162 /* The comparison predicate may be buggy */
164 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
167 while (scm_is_true ((*cmp
) (less
, pivot
, base_ptr
[right
])))
170 /* The comparison predicate may be buggy */
172 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
177 SWAP (base_ptr
[left
], base_ptr
[right
]);
181 else if (left
== right
)
188 while (left
<= right
);
190 /* Set up pointers for next iteration. First determine whether
191 left and right partitions are below the threshold size. If so,
192 ignore one or both. Otherwise, push the larger partition's
193 bounds on the stack and continue sorting the smaller one. */
195 if ((size_t) (right
- lo
) <= MAX_THRESH
)
197 if ((size_t) (hi
- left
) <= MAX_THRESH
)
198 /* Ignore both small partitions. */
201 /* Ignore small left partition. */
204 else if ((size_t) (hi
- left
) <= MAX_THRESH
)
205 /* Ignore small right partition. */
207 else if ((right
- lo
) > (hi
- left
))
209 /* Push larger left partition indices. */
215 /* Push larger right partition indices. */
222 /* Once the BASE_PTR array is partially sorted by quicksort the rest is
223 completely sorted using insertion sort, since this is efficient for
224 partitions below MAX_THRESH size. BASE_PTR points to the beginning of the
225 array to sort, and END idexes the very last element in the array (*not*
230 size_t end
= nr_elems
- 1;
231 size_t thresh
= min (end
, MAX_THRESH
);
234 /* Find smallest element in first threshold and place it at the
235 array's beginning. This is the smallest array element,
236 and the operation speeds up insertion sort's inner loop. */
238 for (run
= tmp
+ 1; run
<= thresh
; run
++)
239 if (scm_is_true ((*cmp
) (less
, base_ptr
[run
], base_ptr
[tmp
])))
243 SWAP (base_ptr
[tmp
], base_ptr
[0]);
245 /* Insertion sort, running from left-hand-side up to right-hand-side. */
253 while (scm_is_true ((*cmp
) (less
, base_ptr
[run
], base_ptr
[tmp
])))
255 /* The comparison predicate may be buggy */
257 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
265 SCM to_insert
= base_ptr
[run
];
268 for (hi
= lo
= run
; --lo
>= tmp
; hi
= lo
)
269 base_ptr
[hi
] = base_ptr
[lo
];
270 base_ptr
[hi
] = to_insert
;
277 static scm_t_trampoline_2
278 compare_function (SCM less
, unsigned int arg_nr
, const char* fname
)
280 const scm_t_trampoline_2 cmp
= scm_trampoline_2 (less
);
281 SCM_ASSERT_TYPE (cmp
!= NULL
, less
, arg_nr
, fname
, "less predicate");
286 /* Question: Is there any need to make this a more general array sort?
287 It is probably enough to manage the vector type. */
288 /* endpos equal as for substring, i.e. endpos is not included. */
289 /* More natural with length? */
291 SCM_DEFINE (scm_restricted_vector_sort_x
, "restricted-vector-sort!", 4, 0, 0,
292 (SCM vec
, SCM less
, SCM startpos
, SCM endpos
),
293 "Sort the vector @var{vec}, using @var{less} for comparing\n"
294 "the vector elements. @var{startpos} (inclusively) and\n"
295 "@var{endpos} (exclusively) delimit\n"
296 "the range of the vector which gets sorted. The return value\n"
298 #define FUNC_NAME s_scm_restricted_vector_sort_x
300 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
301 size_t vlen
, spos
, len
;
304 SCM_VALIDATE_VECTOR (1, vec
);
305 vp
= SCM_WRITABLE_VELTS (vec
); /* vector pointer */
306 vlen
= SCM_VECTOR_LENGTH (vec
);
308 spos
= scm_to_unsigned_integer (startpos
, 0, vlen
);
309 len
= scm_to_unsigned_integer (endpos
, spos
, vlen
) - spos
;
311 quicksort (&vp
[spos
], len
, cmp
, less
);
312 scm_remember_upto_here_1 (vec
);
314 return SCM_UNSPECIFIED
;
319 /* (sorted? sequence less?)
320 * is true when sequence is a list (x0 x1 ... xm) or a vector #(x0 ... xm)
321 * such that for all 1 <= i <= m,
322 * (not (less? (list-ref list i) (list-ref list (- i 1)))). */
323 SCM_DEFINE (scm_sorted_p
, "sorted?", 2, 0, 0,
324 (SCM items
, SCM less
),
325 "Return @code{#t} iff @var{items} is a list or a vector such that\n"
326 "for all 1 <= i <= m, the predicate @var{less} returns true when\n"
327 "applied to all elements i - 1 and i")
328 #define FUNC_NAME s_scm_sorted_p
330 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
331 long len
, j
; /* list/vector length, temp j */
332 SCM item
, rest
; /* rest of items loop variable */
335 if (SCM_NULL_OR_NIL_P (items
))
338 if (scm_is_pair (items
))
340 len
= scm_ilength (items
); /* also checks that it's a pure list */
341 SCM_ASSERT_RANGE (1, items
, len
>= 0);
345 item
= SCM_CAR (items
);
346 rest
= SCM_CDR (items
);
350 if (scm_is_true ((*cmp
) (less
, SCM_CAR (rest
), item
)))
354 item
= SCM_CAR (rest
);
355 rest
= SCM_CDR (rest
);
363 SCM_VALIDATE_VECTOR (1, items
);
365 vp
= SCM_VELTS (items
); /* vector pointer */
366 len
= SCM_VECTOR_LENGTH (items
);
370 if (scm_is_true ((*cmp
) (less
, vp
[1], vp
[0])))
387 takes two lists a and b such that (sorted? a less?) and (sorted? b less?)
388 and returns a new list in which the elements of a and b have been stably
389 interleaved so that (sorted? (merge a b less?) less?).
390 Note: this does _not_ accept vectors. */
391 SCM_DEFINE (scm_merge
, "merge", 3, 0, 0,
392 (SCM alist
, SCM blist
, SCM less
),
393 "Merge two already sorted lists into one.\n"
394 "Given two lists @var{alist} and @var{blist}, such that\n"
395 "@code{(sorted? alist less?)} and @code{(sorted? blist less?)},\n"
396 "return a new list in which the elements of @var{alist} and\n"
397 "@var{blist} have been stably interleaved so that\n"
398 "@code{(sorted? (merge alist blist less?) less?)}.\n"
399 "Note: this does _not_ accept vectors.")
400 #define FUNC_NAME s_scm_merge
404 if (SCM_NULL_OR_NIL_P (alist
))
406 else if (SCM_NULL_OR_NIL_P (blist
))
410 const scm_t_trampoline_2 cmp
= compare_function (less
, 3, FUNC_NAME
);
411 long alen
, blen
; /* list lengths */
414 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (1, alist
, alen
);
415 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, blist
, blen
);
416 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
418 build
= scm_cons (SCM_CAR (blist
), SCM_EOL
);
419 blist
= SCM_CDR (blist
);
424 build
= scm_cons (SCM_CAR (alist
), SCM_EOL
);
425 alist
= SCM_CDR (alist
);
429 while ((alen
> 0) && (blen
> 0))
432 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
434 SCM_SETCDR (last
, scm_cons (SCM_CAR (blist
), SCM_EOL
));
435 blist
= SCM_CDR (blist
);
440 SCM_SETCDR (last
, scm_cons (SCM_CAR (alist
), SCM_EOL
));
441 alist
= SCM_CDR (alist
);
444 last
= SCM_CDR (last
);
446 if ((alen
> 0) && (blen
== 0))
447 SCM_SETCDR (last
, alist
);
448 else if ((alen
== 0) && (blen
> 0))
449 SCM_SETCDR (last
, blist
);
457 scm_merge_list_x (SCM alist
, SCM blist
,
458 long alen
, long blen
,
459 scm_t_trampoline_2 cmp
, SCM less
)
463 if (SCM_NULL_OR_NIL_P (alist
))
465 else if (SCM_NULL_OR_NIL_P (blist
))
469 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
472 blist
= SCM_CDR (blist
);
478 alist
= SCM_CDR (alist
);
482 while ((alen
> 0) && (blen
> 0))
485 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
487 SCM_SETCDR (last
, blist
);
488 blist
= SCM_CDR (blist
);
493 SCM_SETCDR (last
, alist
);
494 alist
= SCM_CDR (alist
);
497 last
= SCM_CDR (last
);
499 if ((alen
> 0) && (blen
== 0))
500 SCM_SETCDR (last
, alist
);
501 else if ((alen
== 0) && (blen
> 0))
502 SCM_SETCDR (last
, blist
);
505 } /* scm_merge_list_x */
508 SCM_DEFINE (scm_merge_x
, "merge!", 3, 0, 0,
509 (SCM alist
, SCM blist
, SCM less
),
510 "Takes two lists @var{alist} and @var{blist} such that\n"
511 "@code{(sorted? alist less?)} and @code{(sorted? blist less?)} and\n"
512 "returns a new list in which the elements of @var{alist} and\n"
513 "@var{blist} have been stably interleaved so that\n"
514 " @code{(sorted? (merge alist blist less?) less?)}.\n"
515 "This is the destructive variant of @code{merge}\n"
516 "Note: this does _not_ accept vectors.")
517 #define FUNC_NAME s_scm_merge_x
519 if (SCM_NULL_OR_NIL_P (alist
))
521 else if (SCM_NULL_OR_NIL_P (blist
))
525 const scm_t_trampoline_2 cmp
= compare_function (less
, 3, FUNC_NAME
);
526 long alen
, blen
; /* list lengths */
527 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (1, alist
, alen
);
528 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, blist
, blen
);
529 return scm_merge_list_x (alist
, blist
, alen
, blen
, cmp
, less
);
535 /* This merge sort algorithm is same as slib's by Richard A. O'Keefe.
536 The algorithm is stable. We also tried to use the algorithm used by
537 scsh's merge-sort but that algorithm showed to not be stable, even
538 though it claimed to be.
541 scm_merge_list_step (SCM
* seq
, scm_t_trampoline_2 cmp
, SCM less
, long n
)
549 a
= scm_merge_list_step (seq
, cmp
, less
, mid
);
550 b
= scm_merge_list_step (seq
, cmp
, less
, n
- mid
);
551 return scm_merge_list_x (a
, b
, mid
, n
- mid
, cmp
, less
);
556 SCM rest
= SCM_CDR (*seq
);
557 SCM x
= SCM_CAR (*seq
);
558 SCM y
= SCM_CAR (SCM_CDR (*seq
));
559 *seq
= SCM_CDR (rest
);
560 SCM_SETCDR (rest
, SCM_EOL
);
561 if (scm_is_true ((*cmp
) (less
, y
, x
)))
564 SCM_SETCAR (rest
, x
);
572 SCM_SETCDR (p
, SCM_EOL
);
577 } /* scm_merge_list_step */
580 SCM_DEFINE (scm_sort_x
, "sort!", 2, 0, 0,
581 (SCM items
, SCM less
),
582 "Sort the sequence @var{items}, which may be a list or a\n"
583 "vector. @var{less} is used for comparing the sequence\n"
584 "elements. The sorting is destructive, that means that the\n"
585 "input sequence is modified to produce the sorted result.\n"
586 "This is not a stable sort.")
587 #define FUNC_NAME s_scm_sort_x
589 long len
; /* list/vector length */
590 if (SCM_NULL_OR_NIL_P (items
))
593 if (scm_is_pair (items
))
595 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
596 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
597 return scm_merge_list_step (&items
, cmp
, less
, len
);
599 else if (SCM_VECTORP (items
))
601 len
= SCM_VECTOR_LENGTH (items
);
602 scm_restricted_vector_sort_x (items
,
605 scm_from_long (len
));
609 SCM_WRONG_TYPE_ARG (1, items
);
614 SCM_DEFINE (scm_sort
, "sort", 2, 0, 0,
615 (SCM items
, SCM less
),
616 "Sort the sequence @var{items}, which may be a list or a\n"
617 "vector. @var{less} is used for comparing the sequence\n"
618 "elements. This is not a stable sort.")
619 #define FUNC_NAME s_scm_sort
621 if (SCM_NULL_OR_NIL_P (items
))
624 if (scm_is_pair (items
))
626 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
629 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
630 items
= scm_list_copy (items
);
631 return scm_merge_list_step (&items
, cmp
, less
, len
);
634 /* support ordinary vectors even if arrays not available? */
635 else if (SCM_VECTORP (items
))
637 long len
= SCM_VECTOR_LENGTH (items
);
638 SCM sortvec
= scm_make_uve (len
, scm_array_prototype (items
));
640 scm_array_copy_x (items
, sortvec
);
641 scm_restricted_vector_sort_x (sortvec
,
644 scm_from_long (len
));
649 SCM_WRONG_TYPE_ARG (1, items
);
655 scm_merge_vector_x (SCM vec
,
657 scm_t_trampoline_2 cmp
,
663 long it
; /* Index for temp vector */
664 long i1
= low
; /* Index for lower vector segment */
665 long i2
= mid
+ 1; /* Index for upper vector segment */
667 /* Copy while both segments contain more characters */
668 for (it
= low
; (i1
<= mid
) && (i2
<= high
); ++it
)
671 Every call of LESS might invoke GC. For full correctness, we
672 should reset the generation of vecbase and tempbase between
676 register SCM
*vp
= SCM_WRITABLE_VELTS(vec
);
678 if (scm_is_true ((*cmp
) (less
, vp
[i2
], vp
[i1
])))
685 register SCM
*vp
= SCM_WRITABLE_VELTS(vec
);
687 /* Copy while first segment contains more characters */
689 temp
[it
++] = vp
[i1
++];
691 /* Copy while second segment contains more characters */
693 temp
[it
++] = vp
[i2
++];
695 /* Copy back from temp to vp */
696 for (it
= low
; it
<= high
; ++it
)
699 } /* scm_merge_vector_x */
703 scm_merge_vector_step (SCM vp
,
705 scm_t_trampoline_2 cmp
,
712 long mid
= (low
+ high
) / 2;
714 scm_merge_vector_step (vp
, temp
, cmp
, less
, low
, mid
);
715 scm_merge_vector_step (vp
, temp
, cmp
, less
, mid
+1, high
);
716 scm_merge_vector_x (vp
, temp
, cmp
, less
, low
, mid
, high
);
718 } /* scm_merge_vector_step */
721 SCM_DEFINE (scm_stable_sort_x
, "stable-sort!", 2, 0, 0,
722 (SCM items
, SCM less
),
723 "Sort the sequence @var{items}, which may be a list or a\n"
724 "vector. @var{less} is used for comparing the sequence elements.\n"
725 "The sorting is destructive, that means that the input sequence\n"
726 "is modified to produce the sorted result.\n"
727 "This is a stable sort.")
728 #define FUNC_NAME s_scm_stable_sort_x
730 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
731 long len
; /* list/vector length */
733 if (SCM_NULL_OR_NIL_P (items
))
736 if (scm_is_pair (items
))
738 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
739 return scm_merge_list_step (&items
, cmp
, less
, len
);
741 else if (SCM_VECTORP (items
))
744 len
= SCM_VECTOR_LENGTH (items
);
747 the following array does not contain any new references to
748 SCM objects, so we can get away with allocing it on the heap.
750 temp
= scm_malloc (len
* sizeof(SCM
));
752 scm_merge_vector_step (items
, temp
, cmp
, less
, 0, len
- 1);
757 SCM_WRONG_TYPE_ARG (1, items
);
762 SCM_DEFINE (scm_stable_sort
, "stable-sort", 2, 0, 0,
763 (SCM items
, SCM less
),
764 "Sort the sequence @var{items}, which may be a list or a\n"
765 "vector. @var{less} is used for comparing the sequence elements.\n"
766 "This is a stable sort.")
767 #define FUNC_NAME s_scm_stable_sort
769 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
771 if (SCM_NULL_OR_NIL_P (items
))
774 if (scm_is_pair (items
))
776 long len
; /* list/vector length */
778 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
779 items
= scm_list_copy (items
);
780 return scm_merge_list_step (&items
, cmp
, less
, len
);
783 /* support ordinary vectors even if arrays not available? */
784 else if (SCM_VECTORP (items
))
786 long len
= SCM_VECTOR_LENGTH (items
);
787 SCM
*temp
= scm_malloc (len
* sizeof (SCM
));
788 SCM retvec
= scm_make_uve (len
, scm_array_prototype (items
));
789 scm_array_copy_x (items
, retvec
);
791 scm_merge_vector_step (retvec
, temp
, cmp
, less
, 0, len
- 1);
797 SCM_WRONG_TYPE_ARG (1, items
);
802 SCM_DEFINE (scm_sort_list_x
, "sort-list!", 2, 0, 0,
803 (SCM items
, SCM less
),
804 "Sort the list @var{items}, using @var{less} for comparing the\n"
805 "list elements. The sorting is destructive, that means that the\n"
806 "input list is modified to produce the sorted result.\n"
807 "This is a stable sort.")
808 #define FUNC_NAME s_scm_sort_list_x
810 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
813 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
814 return scm_merge_list_step (&items
, cmp
, less
, len
);
819 SCM_DEFINE (scm_sort_list
, "sort-list", 2, 0, 0,
820 (SCM items
, SCM less
),
821 "Sort the list @var{items}, using @var{less} for comparing the\n"
822 "list elements. This is a stable sort.")
823 #define FUNC_NAME s_scm_sort_list
825 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
828 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
829 items
= scm_list_copy (items
);
830 return scm_merge_list_step (&items
, cmp
, less
, len
);
838 #include "libguile/sort.x"
840 scm_add_feature ("sort");