1 /* Copyright (C) 1999,2000,2001,2002 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
)
134 /* Select median value from among LO, MID, and HI. Rearrange
135 LO and HI so the three values are sorted. This lowers the
136 probability of picking a pathological pivot value and
137 skips a comparison for both the left and right. */
139 size_t mid
= lo
+ (hi
- lo
) / 2;
141 if (scm_is_true ((*cmp
) (less
, base_ptr
[mid
], base_ptr
[lo
])))
142 SWAP (base_ptr
[mid
], base_ptr
[lo
]);
143 if (scm_is_true ((*cmp
) (less
, base_ptr
[hi
], base_ptr
[mid
])))
144 SWAP (base_ptr
[mid
], base_ptr
[hi
]);
147 if (scm_is_true ((*cmp
) (less
, base_ptr
[mid
], base_ptr
[lo
])))
148 SWAP (base_ptr
[mid
], base_ptr
[lo
]);
151 pivot
= base_ptr
[mid
];
155 /* Here's the famous ``collapse the walls'' section of quicksort.
156 Gotta like those tight inner loops! They are the main reason
157 that this algorithm runs much faster than others. */
160 while (scm_is_true ((*cmp
) (less
, base_ptr
[left
], pivot
)))
163 /* The comparison predicate may be buggy */
165 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
168 while (scm_is_true ((*cmp
) (less
, pivot
, base_ptr
[right
])))
171 /* The comparison predicate may be buggy */
173 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
178 SWAP (base_ptr
[left
], base_ptr
[right
]);
182 else if (left
== right
)
189 while (left
<= right
);
191 /* Set up pointers for next iteration. First determine whether
192 left and right partitions are below the threshold size. If so,
193 ignore one or both. Otherwise, push the larger partition's
194 bounds on the stack and continue sorting the smaller one. */
196 if ((size_t) (right
- lo
) <= MAX_THRESH
)
198 if ((size_t) (hi
- left
) <= MAX_THRESH
)
199 /* Ignore both small partitions. */
202 /* Ignore small left partition. */
205 else if ((size_t) (hi
- left
) <= MAX_THRESH
)
206 /* Ignore small right partition. */
208 else if ((right
- lo
) > (hi
- left
))
210 /* Push larger left partition indices. */
216 /* Push larger right partition indices. */
223 /* Once the BASE_PTR array is partially sorted by quicksort the rest is
224 completely sorted using insertion sort, since this is efficient for
225 partitions below MAX_THRESH size. BASE_PTR points to the beginning of the
226 array to sort, and END idexes the very last element in the array (*not*
231 size_t end
= nr_elems
- 1;
232 size_t thresh
= min (end
, MAX_THRESH
);
235 /* Find smallest element in first threshold and place it at the
236 array's beginning. This is the smallest array element,
237 and the operation speeds up insertion sort's inner loop. */
239 for (run
= tmp
+ 1; run
<= thresh
; run
++)
240 if (scm_is_true ((*cmp
) (less
, base_ptr
[run
], base_ptr
[tmp
])))
244 SWAP (base_ptr
[tmp
], base_ptr
[0]);
246 /* Insertion sort, running from left-hand-side up to right-hand-side. */
254 while (scm_is_true ((*cmp
) (less
, base_ptr
[run
], base_ptr
[tmp
])))
256 /* The comparison predicate may be buggy */
258 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
266 SCM to_insert
= base_ptr
[run
];
269 for (hi
= lo
= run
; --lo
>= tmp
; hi
= lo
)
270 base_ptr
[hi
] = base_ptr
[lo
];
271 base_ptr
[hi
] = to_insert
;
278 static scm_t_trampoline_2
279 compare_function (SCM less
, unsigned int arg_nr
, const char* fname
)
281 const scm_t_trampoline_2 cmp
= scm_trampoline_2 (less
);
282 SCM_ASSERT_TYPE (cmp
!= NULL
, less
, arg_nr
, fname
, "less predicate");
287 /* Question: Is there any need to make this a more general array sort?
288 It is probably enough to manage the vector type. */
289 /* endpos equal as for substring, i.e. endpos is not included. */
290 /* More natural with length? */
292 SCM_DEFINE (scm_restricted_vector_sort_x
, "restricted-vector-sort!", 4, 0, 0,
293 (SCM vec
, SCM less
, SCM startpos
, SCM endpos
),
294 "Sort the vector @var{vec}, using @var{less} for comparing\n"
295 "the vector elements. @var{startpos} (inclusively) and\n"
296 "@var{endpos} (exclusively) delimit\n"
297 "the range of the vector which gets sorted. The return value\n"
299 #define FUNC_NAME s_scm_restricted_vector_sort_x
301 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
302 size_t vlen
, spos
, len
;
305 SCM_VALIDATE_VECTOR (1, vec
);
306 vp
= SCM_WRITABLE_VELTS (vec
); /* vector pointer */
307 vlen
= SCM_VECTOR_LENGTH (vec
);
309 spos
= scm_to_unsigned_integer (startpos
, 0, vlen
);
310 len
= scm_to_unsigned_integer (endpos
, spos
, vlen
) - spos
;
312 quicksort (&vp
[spos
], len
, cmp
, less
);
313 scm_remember_upto_here_1 (vec
);
315 return SCM_UNSPECIFIED
;
320 /* (sorted? sequence less?)
321 * is true when sequence is a list (x0 x1 ... xm) or a vector #(x0 ... xm)
322 * such that for all 1 <= i <= m,
323 * (not (less? (list-ref list i) (list-ref list (- i 1)))). */
324 SCM_DEFINE (scm_sorted_p
, "sorted?", 2, 0, 0,
325 (SCM items
, SCM less
),
326 "Return @code{#t} iff @var{items} is a list or a vector such that\n"
327 "for all 1 <= i <= m, the predicate @var{less} returns true when\n"
328 "applied to all elements i - 1 and i")
329 #define FUNC_NAME s_scm_sorted_p
331 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
332 long len
, j
; /* list/vector length, temp j */
333 SCM item
, rest
; /* rest of items loop variable */
336 if (SCM_NULL_OR_NIL_P (items
))
339 if (scm_is_pair (items
))
341 len
= scm_ilength (items
); /* also checks that it's a pure list */
342 SCM_ASSERT_RANGE (1, items
, len
>= 0);
346 item
= SCM_CAR (items
);
347 rest
= SCM_CDR (items
);
351 if (scm_is_true ((*cmp
) (less
, SCM_CAR (rest
), item
)))
355 item
= SCM_CAR (rest
);
356 rest
= SCM_CDR (rest
);
364 SCM_VALIDATE_VECTOR (1, items
);
366 vp
= SCM_VELTS (items
); /* vector pointer */
367 len
= SCM_VECTOR_LENGTH (items
);
371 if (scm_is_true ((*cmp
) (less
, vp
[1], vp
[0])))
388 takes two lists a and b such that (sorted? a less?) and (sorted? b less?)
389 and returns a new list in which the elements of a and b have been stably
390 interleaved so that (sorted? (merge a b less?) less?).
391 Note: this does _not_ accept vectors. */
392 SCM_DEFINE (scm_merge
, "merge", 3, 0, 0,
393 (SCM alist
, SCM blist
, SCM less
),
394 "Merge two already sorted lists into one.\n"
395 "Given two lists @var{alist} and @var{blist}, such that\n"
396 "@code{(sorted? alist less?)} and @code{(sorted? blist less?)},\n"
397 "return a new list in which the elements of @var{alist} and\n"
398 "@var{blist} have been stably interleaved so that\n"
399 "@code{(sorted? (merge alist blist less?) less?)}.\n"
400 "Note: this does _not_ accept vectors.")
401 #define FUNC_NAME s_scm_merge
405 if (SCM_NULL_OR_NIL_P (alist
))
407 else if (SCM_NULL_OR_NIL_P (blist
))
411 const scm_t_trampoline_2 cmp
= compare_function (less
, 3, FUNC_NAME
);
412 long alen
, blen
; /* list lengths */
415 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (1, alist
, alen
);
416 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, blist
, blen
);
417 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
419 build
= scm_cons (SCM_CAR (blist
), SCM_EOL
);
420 blist
= SCM_CDR (blist
);
425 build
= scm_cons (SCM_CAR (alist
), SCM_EOL
);
426 alist
= SCM_CDR (alist
);
430 while ((alen
> 0) && (blen
> 0))
433 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
435 SCM_SETCDR (last
, scm_cons (SCM_CAR (blist
), SCM_EOL
));
436 blist
= SCM_CDR (blist
);
441 SCM_SETCDR (last
, scm_cons (SCM_CAR (alist
), SCM_EOL
));
442 alist
= SCM_CDR (alist
);
445 last
= SCM_CDR (last
);
447 if ((alen
> 0) && (blen
== 0))
448 SCM_SETCDR (last
, alist
);
449 else if ((alen
== 0) && (blen
> 0))
450 SCM_SETCDR (last
, blist
);
458 scm_merge_list_x (SCM alist
, SCM blist
,
459 long alen
, long blen
,
460 scm_t_trampoline_2 cmp
, SCM less
)
464 if (SCM_NULL_OR_NIL_P (alist
))
466 else if (SCM_NULL_OR_NIL_P (blist
))
470 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
473 blist
= SCM_CDR (blist
);
479 alist
= SCM_CDR (alist
);
483 while ((alen
> 0) && (blen
> 0))
486 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
488 SCM_SETCDR (last
, blist
);
489 blist
= SCM_CDR (blist
);
494 SCM_SETCDR (last
, alist
);
495 alist
= SCM_CDR (alist
);
498 last
= SCM_CDR (last
);
500 if ((alen
> 0) && (blen
== 0))
501 SCM_SETCDR (last
, alist
);
502 else if ((alen
== 0) && (blen
> 0))
503 SCM_SETCDR (last
, blist
);
506 } /* scm_merge_list_x */
509 SCM_DEFINE (scm_merge_x
, "merge!", 3, 0, 0,
510 (SCM alist
, SCM blist
, SCM less
),
511 "Takes two lists @var{alist} and @var{blist} such that\n"
512 "@code{(sorted? alist less?)} and @code{(sorted? blist less?)} and\n"
513 "returns a new list in which the elements of @var{alist} and\n"
514 "@var{blist} have been stably interleaved so that\n"
515 " @code{(sorted? (merge alist blist less?) less?)}.\n"
516 "This is the destructive variant of @code{merge}\n"
517 "Note: this does _not_ accept vectors.")
518 #define FUNC_NAME s_scm_merge_x
520 if (SCM_NULL_OR_NIL_P (alist
))
522 else if (SCM_NULL_OR_NIL_P (blist
))
526 const scm_t_trampoline_2 cmp
= compare_function (less
, 3, FUNC_NAME
);
527 long alen
, blen
; /* list lengths */
528 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (1, alist
, alen
);
529 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, blist
, blen
);
530 return scm_merge_list_x (alist
, blist
, alen
, blen
, cmp
, less
);
536 /* This merge sort algorithm is same as slib's by Richard A. O'Keefe.
537 The algorithm is stable. We also tried to use the algorithm used by
538 scsh's merge-sort but that algorithm showed to not be stable, even
539 though it claimed to be.
542 scm_merge_list_step (SCM
* seq
, scm_t_trampoline_2 cmp
, SCM less
, long n
)
550 a
= scm_merge_list_step (seq
, cmp
, less
, mid
);
551 b
= scm_merge_list_step (seq
, cmp
, less
, n
- mid
);
552 return scm_merge_list_x (a
, b
, mid
, n
- mid
, cmp
, less
);
557 SCM rest
= SCM_CDR (*seq
);
558 SCM x
= SCM_CAR (*seq
);
559 SCM y
= SCM_CAR (SCM_CDR (*seq
));
560 *seq
= SCM_CDR (rest
);
561 SCM_SETCDR (rest
, SCM_EOL
);
562 if (scm_is_true ((*cmp
) (less
, y
, x
)))
565 SCM_SETCAR (rest
, x
);
573 SCM_SETCDR (p
, SCM_EOL
);
578 } /* scm_merge_list_step */
581 SCM_DEFINE (scm_sort_x
, "sort!", 2, 0, 0,
582 (SCM items
, SCM less
),
583 "Sort the sequence @var{items}, which may be a list or a\n"
584 "vector. @var{less} is used for comparing the sequence\n"
585 "elements. The sorting is destructive, that means that the\n"
586 "input sequence is modified to produce the sorted result.\n"
587 "This is not a stable sort.")
588 #define FUNC_NAME s_scm_sort_x
590 long len
; /* list/vector length */
591 if (SCM_NULL_OR_NIL_P (items
))
594 if (scm_is_pair (items
))
596 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
597 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
598 return scm_merge_list_step (&items
, cmp
, less
, len
);
600 else if (SCM_VECTORP (items
))
602 len
= SCM_VECTOR_LENGTH (items
);
603 scm_restricted_vector_sort_x (items
,
606 scm_from_long (len
));
610 SCM_WRONG_TYPE_ARG (1, items
);
615 SCM_DEFINE (scm_sort
, "sort", 2, 0, 0,
616 (SCM items
, SCM less
),
617 "Sort the sequence @var{items}, which may be a list or a\n"
618 "vector. @var{less} is used for comparing the sequence\n"
619 "elements. This is not a stable sort.")
620 #define FUNC_NAME s_scm_sort
622 if (SCM_NULL_OR_NIL_P (items
))
625 if (scm_is_pair (items
))
627 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
630 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
631 items
= scm_list_copy (items
);
632 return scm_merge_list_step (&items
, cmp
, less
, len
);
635 /* support ordinary vectors even if arrays not available? */
636 else if (SCM_VECTORP (items
))
638 long len
= SCM_VECTOR_LENGTH (items
);
639 SCM sortvec
= scm_make_uve (len
, scm_array_prototype (items
));
641 scm_array_copy_x (items
, sortvec
);
642 scm_restricted_vector_sort_x (sortvec
,
645 scm_from_long (len
));
650 SCM_WRONG_TYPE_ARG (1, items
);
656 scm_merge_vector_x (SCM vec
,
658 scm_t_trampoline_2 cmp
,
664 long it
; /* Index for temp vector */
665 long i1
= low
; /* Index for lower vector segment */
666 long i2
= mid
+ 1; /* Index for upper vector segment */
668 /* Copy while both segments contain more characters */
669 for (it
= low
; (i1
<= mid
) && (i2
<= high
); ++it
)
672 Every call of LESS might invoke GC. For full correctness, we
673 should reset the generation of vecbase and tempbase between
677 register SCM
*vp
= SCM_WRITABLE_VELTS(vec
);
679 if (scm_is_true ((*cmp
) (less
, vp
[i2
], vp
[i1
])))
686 register SCM
*vp
= SCM_WRITABLE_VELTS(vec
);
688 /* Copy while first segment contains more characters */
690 temp
[it
++] = vp
[i1
++];
692 /* Copy while second segment contains more characters */
694 temp
[it
++] = vp
[i2
++];
696 /* Copy back from temp to vp */
697 for (it
= low
; it
<= high
; ++it
)
700 } /* scm_merge_vector_x */
704 scm_merge_vector_step (SCM vp
,
706 scm_t_trampoline_2 cmp
,
713 long mid
= (low
+ high
) / 2;
715 scm_merge_vector_step (vp
, temp
, cmp
, less
, low
, mid
);
716 scm_merge_vector_step (vp
, temp
, cmp
, less
, mid
+1, high
);
717 scm_merge_vector_x (vp
, temp
, cmp
, less
, low
, mid
, high
);
719 } /* scm_merge_vector_step */
722 SCM_DEFINE (scm_stable_sort_x
, "stable-sort!", 2, 0, 0,
723 (SCM items
, SCM less
),
724 "Sort the sequence @var{items}, which may be a list or a\n"
725 "vector. @var{less} is used for comparing the sequence elements.\n"
726 "The sorting is destructive, that means that the input sequence\n"
727 "is modified to produce the sorted result.\n"
728 "This is a stable sort.")
729 #define FUNC_NAME s_scm_stable_sort_x
731 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
732 long len
; /* list/vector length */
734 if (SCM_NULL_OR_NIL_P (items
))
737 if (scm_is_pair (items
))
739 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
740 return scm_merge_list_step (&items
, cmp
, less
, len
);
742 else if (SCM_VECTORP (items
))
745 len
= SCM_VECTOR_LENGTH (items
);
748 the following array does not contain any new references to
749 SCM objects, so we can get away with allocing it on the heap.
751 temp
= scm_malloc (len
* sizeof(SCM
));
753 scm_merge_vector_step (items
, temp
, cmp
, less
, 0, len
- 1);
758 SCM_WRONG_TYPE_ARG (1, items
);
763 SCM_DEFINE (scm_stable_sort
, "stable-sort", 2, 0, 0,
764 (SCM items
, SCM less
),
765 "Sort the sequence @var{items}, which may be a list or a\n"
766 "vector. @var{less} is used for comparing the sequence elements.\n"
767 "This is a stable sort.")
768 #define FUNC_NAME s_scm_stable_sort
770 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
772 if (SCM_NULL_OR_NIL_P (items
))
775 if (scm_is_pair (items
))
777 long len
; /* list/vector length */
779 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
780 items
= scm_list_copy (items
);
781 return scm_merge_list_step (&items
, cmp
, less
, len
);
784 /* support ordinary vectors even if arrays not available? */
785 else if (SCM_VECTORP (items
))
787 long len
= SCM_VECTOR_LENGTH (items
);
788 SCM
*temp
= scm_malloc (len
* sizeof (SCM
));
789 SCM retvec
= scm_make_uve (len
, scm_array_prototype (items
));
790 scm_array_copy_x (items
, retvec
);
792 scm_merge_vector_step (retvec
, temp
, cmp
, less
, 0, len
- 1);
798 SCM_WRONG_TYPE_ARG (1, items
);
803 SCM_DEFINE (scm_sort_list_x
, "sort-list!", 2, 0, 0,
804 (SCM items
, SCM less
),
805 "Sort the list @var{items}, using @var{less} for comparing the\n"
806 "list elements. The sorting is destructive, that means that the\n"
807 "input list is modified to produce the sorted result.\n"
808 "This is a stable sort.")
809 #define FUNC_NAME s_scm_sort_list_x
811 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
814 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
815 return scm_merge_list_step (&items
, cmp
, less
, len
);
820 SCM_DEFINE (scm_sort_list
, "sort-list", 2, 0, 0,
821 (SCM items
, SCM less
),
822 "Sort the list @var{items}, using @var{less} for comparing the\n"
823 "list elements. This is a stable sort.")
824 #define FUNC_NAME s_scm_sort_list
826 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
829 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
830 items
= scm_list_copy (items
);
831 return scm_merge_list_step (&items
, cmp
, less
, len
);
839 #include "libguile/sort.x"
841 scm_add_feature ("sort");