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"
43 #include "libguile/validate.h"
44 #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
)
131 /* Select median value from among LO, MID, and HI. Rearrange
132 LO and HI so the three values are sorted. This lowers the
133 probability of picking a pathological pivot value and
134 skips a comparison for both the left and right. */
136 size_t mid
= lo
+ (hi
- lo
) / 2;
138 if (scm_is_true ((*cmp
) (less
, base_ptr
[mid
], base_ptr
[lo
])))
139 SWAP (base_ptr
[mid
], base_ptr
[lo
]);
140 if (scm_is_true ((*cmp
) (less
, base_ptr
[hi
], base_ptr
[mid
])))
141 SWAP (base_ptr
[mid
], base_ptr
[hi
]);
144 if (scm_is_true ((*cmp
) (less
, base_ptr
[mid
], base_ptr
[lo
])))
145 SWAP (base_ptr
[mid
], base_ptr
[lo
]);
151 /* Here's the famous ``collapse the walls'' section of quicksort.
152 Gotta like those tight inner loops! They are the main reason
153 that this algorithm runs much faster than others. */
156 while (scm_is_true ((*cmp
) (less
, base_ptr
[left
], base_ptr
[mid
])))
159 /* The comparison predicate may be buggy */
161 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
164 while (scm_is_true ((*cmp
) (less
, base_ptr
[mid
], base_ptr
[right
])))
167 /* The comparison predicate may be buggy */
169 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
174 SWAP (base_ptr
[left
], base_ptr
[right
]);
178 else if (left
== right
)
185 while (left
<= right
);
187 /* Set up pointers for next iteration. First determine whether
188 left and right partitions are below the threshold size. If so,
189 ignore one or both. Otherwise, push the larger partition's
190 bounds on the stack and continue sorting the smaller one. */
192 if ((size_t) (right
- lo
) <= MAX_THRESH
)
194 if ((size_t) (hi
- left
) <= MAX_THRESH
)
195 /* Ignore both small partitions. */
198 /* Ignore small left partition. */
201 else if ((size_t) (hi
- left
) <= MAX_THRESH
)
202 /* Ignore small right partition. */
204 else if ((right
- lo
) > (hi
- left
))
206 /* Push larger left partition indices. */
212 /* Push larger right partition indices. */
219 /* Once the BASE_PTR array is partially sorted by quicksort the rest is
220 completely sorted using insertion sort, since this is efficient for
221 partitions below MAX_THRESH size. BASE_PTR points to the beginning of the
222 array to sort, and END idexes the very last element in the array (*not*
227 size_t end
= nr_elems
- 1;
228 size_t thresh
= min (end
, MAX_THRESH
);
231 /* Find smallest element in first threshold and place it at the
232 array's beginning. This is the smallest array element,
233 and the operation speeds up insertion sort's inner loop. */
235 for (run
= tmp
+ 1; run
<= thresh
; run
++)
236 if (scm_is_true ((*cmp
) (less
, base_ptr
[run
], base_ptr
[tmp
])))
240 SWAP (base_ptr
[tmp
], base_ptr
[0]);
242 /* Insertion sort, running from left-hand-side up to right-hand-side. */
248 while (scm_is_true ((*cmp
) (less
, base_ptr
[run
], base_ptr
[tmp
])))
250 /* The comparison predicate may be buggy */
252 scm_misc_error (NULL
, s_buggy_less
, SCM_EOL
);
260 SCM to_insert
= base_ptr
[run
];
263 for (hi
= lo
= run
; --lo
>= tmp
; hi
= lo
)
264 base_ptr
[hi
] = base_ptr
[lo
];
265 base_ptr
[hi
] = to_insert
;
272 static scm_t_trampoline_2
273 compare_function (SCM less
, unsigned int arg_nr
, const char* fname
)
275 const scm_t_trampoline_2 cmp
= scm_trampoline_2 (less
);
276 SCM_ASSERT_TYPE (cmp
!= NULL
, less
, arg_nr
, fname
, "less predicate");
281 /* Question: Is there any need to make this a more general array sort?
282 It is probably enough to manage the vector type. */
283 /* endpos equal as for substring, i.e. endpos is not included. */
284 /* More natural with length? */
286 SCM_DEFINE (scm_restricted_vector_sort_x
, "restricted-vector-sort!", 4, 0, 0,
287 (SCM vec
, SCM less
, SCM startpos
, SCM endpos
),
288 "Sort the vector @var{vec}, using @var{less} for comparing\n"
289 "the vector elements. @var{startpos} and @var{endpos} delimit\n"
290 "the range of the vector which gets sorted. The return value\n"
292 #define FUNC_NAME s_scm_restricted_vector_sort_x
294 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
295 size_t vlen
, spos
, len
;
298 SCM_VALIDATE_VECTOR (1, vec
);
299 vp
= SCM_WRITABLE_VELTS (vec
); /* vector pointer */
300 vlen
= SCM_VECTOR_LENGTH (vec
);
302 spos
= scm_to_unsigned_integer (startpos
, 0, vlen
);
303 len
= scm_to_unsigned_integer (endpos
, 0, vlen
) - spos
;
305 quicksort (&vp
[spos
], len
, cmp
, less
);
306 scm_remember_upto_here_1 (vec
);
308 return SCM_UNSPECIFIED
;
313 /* (sorted? sequence less?)
314 * is true when sequence is a list (x0 x1 ... xm) or a vector #(x0 ... xm)
315 * such that for all 1 <= i <= m,
316 * (not (less? (list-ref list i) (list-ref list (- i 1)))). */
317 SCM_DEFINE (scm_sorted_p
, "sorted?", 2, 0, 0,
318 (SCM items
, SCM less
),
319 "Return @code{#t} iff @var{items} is a list or a vector such that\n"
320 "for all 1 <= i <= m, the predicate @var{less} returns true when\n"
321 "applied to all elements i - 1 and i")
322 #define FUNC_NAME s_scm_sorted_p
324 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
325 long len
, j
; /* list/vector length, temp j */
326 SCM item
, rest
; /* rest of items loop variable */
329 if (SCM_NULL_OR_NIL_P (items
))
332 if (SCM_CONSP (items
))
334 len
= scm_ilength (items
); /* also checks that it's a pure list */
335 SCM_ASSERT_RANGE (1, items
, len
>= 0);
339 item
= SCM_CAR (items
);
340 rest
= SCM_CDR (items
);
344 if (scm_is_true ((*cmp
) (less
, SCM_CAR (rest
), item
)))
348 item
= SCM_CAR (rest
);
349 rest
= SCM_CDR (rest
);
357 SCM_VALIDATE_VECTOR (1, items
);
359 vp
= SCM_VELTS (items
); /* vector pointer */
360 len
= SCM_VECTOR_LENGTH (items
);
364 if (scm_is_true ((*cmp
) (less
, vp
[1], vp
[0])))
381 takes two lists a and b such that (sorted? a less?) and (sorted? b less?)
382 and returns a new list in which the elements of a and b have been stably
383 interleaved so that (sorted? (merge a b less?) less?).
384 Note: this does _not_ accept vectors. */
385 SCM_DEFINE (scm_merge
, "merge", 3, 0, 0,
386 (SCM alist
, SCM blist
, SCM less
),
387 "Merge two already sorted lists into one.\n"
388 "Given two lists @var{alist} and @var{blist}, such that\n"
389 "@code{(sorted? alist less?)} and @code{(sorted? blist less?)},\n"
390 "return a new list in which the elements of @var{alist} and\n"
391 "@var{blist} have been stably interleaved so that\n"
392 "@code{(sorted? (merge alist blist less?) less?)}.\n"
393 "Note: this does _not_ accept vectors.")
394 #define FUNC_NAME s_scm_merge
398 if (SCM_NULL_OR_NIL_P (alist
))
400 else if (SCM_NULL_OR_NIL_P (blist
))
404 const scm_t_trampoline_2 cmp
= compare_function (less
, 3, FUNC_NAME
);
405 long alen
, blen
; /* list lengths */
408 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (1, alist
, alen
);
409 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, blist
, blen
);
410 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
412 build
= scm_cons (SCM_CAR (blist
), SCM_EOL
);
413 blist
= SCM_CDR (blist
);
418 build
= scm_cons (SCM_CAR (alist
), SCM_EOL
);
419 alist
= SCM_CDR (alist
);
423 while ((alen
> 0) && (blen
> 0))
425 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
427 SCM_SETCDR (last
, scm_cons (SCM_CAR (blist
), SCM_EOL
));
428 blist
= SCM_CDR (blist
);
433 SCM_SETCDR (last
, scm_cons (SCM_CAR (alist
), SCM_EOL
));
434 alist
= SCM_CDR (alist
);
437 last
= SCM_CDR (last
);
439 if ((alen
> 0) && (blen
== 0))
440 SCM_SETCDR (last
, alist
);
441 else if ((alen
== 0) && (blen
> 0))
442 SCM_SETCDR (last
, blist
);
450 scm_merge_list_x (SCM alist
, SCM blist
,
451 long alen
, long blen
,
452 scm_t_trampoline_2 cmp
, SCM less
)
456 if (SCM_NULL_OR_NIL_P (alist
))
458 else if (SCM_NULL_OR_NIL_P (blist
))
462 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
465 blist
= SCM_CDR (blist
);
471 alist
= SCM_CDR (alist
);
475 while ((alen
> 0) && (blen
> 0))
477 if (scm_is_true ((*cmp
) (less
, SCM_CAR (blist
), SCM_CAR (alist
))))
479 SCM_SETCDR (last
, blist
);
480 blist
= SCM_CDR (blist
);
485 SCM_SETCDR (last
, alist
);
486 alist
= SCM_CDR (alist
);
489 last
= SCM_CDR (last
);
491 if ((alen
> 0) && (blen
== 0))
492 SCM_SETCDR (last
, alist
);
493 else if ((alen
== 0) && (blen
> 0))
494 SCM_SETCDR (last
, blist
);
497 } /* scm_merge_list_x */
500 SCM_DEFINE (scm_merge_x
, "merge!", 3, 0, 0,
501 (SCM alist
, SCM blist
, SCM less
),
502 "Takes two lists @var{alist} and @var{blist} such that\n"
503 "@code{(sorted? alist less?)} and @code{(sorted? blist less?)} and\n"
504 "returns a new list in which the elements of @var{alist} and\n"
505 "@var{blist} have been stably interleaved so that\n"
506 " @code{(sorted? (merge alist blist less?) less?)}.\n"
507 "This is the destructive variant of @code{merge}\n"
508 "Note: this does _not_ accept vectors.")
509 #define FUNC_NAME s_scm_merge_x
511 if (SCM_NULL_OR_NIL_P (alist
))
513 else if (SCM_NULL_OR_NIL_P (blist
))
517 const scm_t_trampoline_2 cmp
= compare_function (less
, 3, FUNC_NAME
);
518 long alen
, blen
; /* list lengths */
519 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (1, alist
, alen
);
520 SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, blist
, blen
);
521 return scm_merge_list_x (alist
, blist
, alen
, blen
, cmp
, less
);
527 /* This merge sort algorithm is same as slib's by Richard A. O'Keefe.
528 The algorithm is stable. We also tried to use the algorithm used by
529 scsh's merge-sort but that algorithm showed to not be stable, even
530 though it claimed to be.
533 scm_merge_list_step (SCM
* seq
, scm_t_trampoline_2 cmp
, SCM less
, long n
)
540 a
= scm_merge_list_step (seq
, cmp
, less
, mid
);
541 b
= scm_merge_list_step (seq
, cmp
, less
, n
- mid
);
542 return scm_merge_list_x (a
, b
, mid
, n
- mid
, cmp
, less
);
547 SCM rest
= SCM_CDR (*seq
);
548 SCM x
= SCM_CAR (*seq
);
549 SCM y
= SCM_CAR (SCM_CDR (*seq
));
550 *seq
= SCM_CDR (rest
);
551 SCM_SETCDR (rest
, SCM_EOL
);
552 if (scm_is_true ((*cmp
) (less
, y
, x
)))
555 SCM_SETCAR (rest
, x
);
563 SCM_SETCDR (p
, SCM_EOL
);
568 } /* scm_merge_list_step */
571 SCM_DEFINE (scm_sort_x
, "sort!", 2, 0, 0,
572 (SCM items
, SCM less
),
573 "Sort the sequence @var{items}, which may be a list or a\n"
574 "vector. @var{less} is used for comparing the sequence\n"
575 "elements. The sorting is destructive, that means that the\n"
576 "input sequence is modified to produce the sorted result.\n"
577 "This is not a stable sort.")
578 #define FUNC_NAME s_scm_sort_x
580 long len
; /* list/vector length */
581 if (SCM_NULL_OR_NIL_P (items
))
584 if (SCM_CONSP (items
))
586 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
587 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
588 return scm_merge_list_step (&items
, cmp
, less
, len
);
590 else if (SCM_VECTORP (items
))
592 len
= SCM_VECTOR_LENGTH (items
);
593 scm_restricted_vector_sort_x (items
,
596 SCM_I_MAKINUM (len
));
600 SCM_WRONG_TYPE_ARG (1, items
);
605 SCM_DEFINE (scm_sort
, "sort", 2, 0, 0,
606 (SCM items
, SCM less
),
607 "Sort the sequence @var{items}, which may be a list or a\n"
608 "vector. @var{less} is used for comparing the sequence\n"
609 "elements. This is not a stable sort.")
610 #define FUNC_NAME s_scm_sort
612 if (SCM_NULL_OR_NIL_P (items
))
615 if (SCM_CONSP (items
))
617 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
620 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
621 items
= scm_list_copy (items
);
622 return scm_merge_list_step (&items
, cmp
, less
, len
);
625 /* support ordinary vectors even if arrays not available? */
626 else if (SCM_VECTORP (items
))
628 long len
= SCM_VECTOR_LENGTH (items
);
629 SCM sortvec
= scm_make_uve (len
, scm_array_prototype (items
));
631 scm_array_copy_x (items
, sortvec
);
632 scm_restricted_vector_sort_x (sortvec
,
635 SCM_I_MAKINUM (len
));
640 SCM_WRONG_TYPE_ARG (1, items
);
646 scm_merge_vector_x (SCM vec
,
648 scm_t_trampoline_2 cmp
,
654 long it
; /* Index for temp vector */
655 long i1
= low
; /* Index for lower vector segment */
656 long i2
= mid
+ 1; /* Index for upper vector segment */
658 /* Copy while both segments contain more characters */
659 for (it
= low
; (i1
<= mid
) && (i2
<= high
); ++it
)
662 Every call of LESS might invoke GC. For full correctness, we
663 should reset the generation of vecbase and tempbase between
667 register SCM
*vp
= SCM_WRITABLE_VELTS(vec
);
669 if (scm_is_true ((*cmp
) (less
, vp
[i2
], vp
[i1
])))
676 register SCM
*vp
= SCM_WRITABLE_VELTS(vec
);
678 /* Copy while first segment contains more characters */
680 temp
[it
++] = vp
[i1
++];
682 /* Copy while second segment contains more characters */
684 temp
[it
++] = vp
[i2
++];
686 /* Copy back from temp to vp */
687 for (it
= low
; it
<= high
; ++it
)
690 } /* scm_merge_vector_x */
694 scm_merge_vector_step (SCM vp
,
696 scm_t_trampoline_2 cmp
,
703 long mid
= (low
+ high
) / 2;
704 scm_merge_vector_step (vp
, temp
, cmp
, less
, low
, mid
);
705 scm_merge_vector_step (vp
, temp
, cmp
, less
, mid
+1, high
);
706 scm_merge_vector_x (vp
, temp
, cmp
, less
, low
, mid
, high
);
708 } /* scm_merge_vector_step */
711 SCM_DEFINE (scm_stable_sort_x
, "stable-sort!", 2, 0, 0,
712 (SCM items
, SCM less
),
713 "Sort the sequence @var{items}, which may be a list or a\n"
714 "vector. @var{less} is used for comparing the sequence elements.\n"
715 "The sorting is destructive, that means that the input sequence\n"
716 "is modified to produce the sorted result.\n"
717 "This is a stable sort.")
718 #define FUNC_NAME s_scm_stable_sort_x
720 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
721 long len
; /* list/vector length */
723 if (SCM_NULL_OR_NIL_P (items
))
726 if (SCM_CONSP (items
))
728 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
729 return scm_merge_list_step (&items
, cmp
, less
, len
);
731 else if (SCM_VECTORP (items
))
734 len
= SCM_VECTOR_LENGTH (items
);
737 the following array does not contain any new references to
738 SCM objects, so we can get away with allocing it on the heap.
740 temp
= scm_malloc (len
* sizeof(SCM
));
742 scm_merge_vector_step (items
, temp
, cmp
, less
, 0, len
- 1);
747 SCM_WRONG_TYPE_ARG (1, items
);
752 SCM_DEFINE (scm_stable_sort
, "stable-sort", 2, 0, 0,
753 (SCM items
, SCM less
),
754 "Sort the sequence @var{items}, which may be a list or a\n"
755 "vector. @var{less} is used for comparing the sequence elements.\n"
756 "This is a stable sort.")
757 #define FUNC_NAME s_scm_stable_sort
759 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
761 if (SCM_NULL_OR_NIL_P (items
))
764 if (SCM_CONSP (items
))
766 long len
; /* list/vector length */
768 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
769 items
= scm_list_copy (items
);
770 return scm_merge_list_step (&items
, cmp
, less
, len
);
773 /* support ordinary vectors even if arrays not available? */
774 else if (SCM_VECTORP (items
))
776 long len
= SCM_VECTOR_LENGTH (items
);
777 SCM
*temp
= scm_malloc (len
* sizeof (SCM
));
778 SCM retvec
= scm_make_uve (len
, scm_array_prototype (items
));
779 scm_array_copy_x (items
, retvec
);
781 scm_merge_vector_step (retvec
, temp
, cmp
, less
, 0, len
- 1);
787 SCM_WRONG_TYPE_ARG (1, items
);
792 SCM_DEFINE (scm_sort_list_x
, "sort-list!", 2, 0, 0,
793 (SCM items
, SCM less
),
794 "Sort the list @var{items}, using @var{less} for comparing the\n"
795 "list elements. The sorting is destructive, that means that the\n"
796 "input list is modified to produce the sorted result.\n"
797 "This is a stable sort.")
798 #define FUNC_NAME s_scm_sort_list_x
800 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
803 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
804 return scm_merge_list_step (&items
, cmp
, less
, len
);
809 SCM_DEFINE (scm_sort_list
, "sort-list", 2, 0, 0,
810 (SCM items
, SCM less
),
811 "Sort the list @var{items}, using @var{less} for comparing the\n"
812 "list elements. This is a stable sort.")
813 #define FUNC_NAME s_scm_sort_list
815 const scm_t_trampoline_2 cmp
= compare_function (less
, 2, FUNC_NAME
);
818 SCM_VALIDATE_LIST_COPYLEN (1, items
, len
);
819 items
= scm_list_copy (items
);
820 return scm_merge_list_step (&items
, cmp
, less
, len
);
828 #include "libguile/sort.x"
830 scm_add_feature ("sort");