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srfi-1: Rewrite 'find-tail' in Scheme.

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* libguile/srfi-1.c (scm_srfi1_find_tail): Remove.
* libguile/srfi-1.h (scm_srfi1_find_tail): Likewise.
* module/srfi/srfi-1.scm (find-tail): New procedure.
This commit is contained in:
Ludovic Courtès 2020-06-17 17:33:28 +02:00
parent 0360843ace
commit cd4c747fb8
3 changed files with 11 additions and 19 deletions
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18
libguile/srfi-1.c
View file

@ -575,24 +575,6 @@ SCM_DEFINE (scm_srfi1_delete_duplicates_x, "delete-duplicates!", 1, 1, 0,
}
#undef FUNC_NAME
SCM_DEFINE (scm_srfi1_find_tail, "find-tail", 2, 0, 0,
(SCM pred, SCM lst),
"Return the first pair of @var{lst} whose @sc{car} satisfies the\n"
"predicate @var{pred}, or return @code{#f} if no such element is\n"
"found.")
#define FUNC_NAME s_scm_srfi1_find_tail
{
SCM_VALIDATE_PROC (SCM_ARG1, pred);
for ( ; scm_is_pair (lst); lst = SCM_CDR (lst))
if (scm_is_true (scm_call_1 (pred, SCM_CAR (lst))))
return lst;
SCM_ASSERT_TYPE (SCM_NULL_OR_NIL_P (lst), lst, SCM_ARG2, FUNC_NAME, "list");
return SCM_BOOL_F;
}
#undef FUNC_NAME
SCM_DEFINE (scm_srfi1_length_plus, "length+", 1, 0, 0,
(SCM lst),
"Return the length of @var{lst}, or @code{#f} if @var{lst} is\n"

1
libguile/srfi-1.h
View file

@ -33,7 +33,6 @@ SCM_INTERNAL SCM scm_srfi1_delete (SCM x, SCM lst, SCM pred);
SCM_INTERNAL SCM scm_srfi1_delete_x (SCM x, SCM lst, SCM pred);
SCM_INTERNAL SCM scm_srfi1_delete_duplicates (SCM lst, SCM pred);
SCM_INTERNAL SCM scm_srfi1_delete_duplicates_x (SCM lst, SCM pred);
SCM_INTERNAL SCM scm_srfi1_find_tail (SCM pred, SCM lst);
SCM_INTERNAL SCM scm_srfi1_length_plus (SCM lst);
SCM_INTERNAL SCM scm_srfi1_lset_difference_x (SCM equal, SCM lst, SCM rest);
SCM_INTERNAL SCM scm_srfi1_list_copy (SCM lst);

11
module/srfi/srfi-1.scm
View file

@ -731,6 +731,17 @@ the list returned."
head
(loop (cdr lst)))))))
(define (find-tail pred lst)
"Return the first pair of @var{lst} whose @sc{car} satisfies the
predicate @var{pred}, or return @code{#f} if no such element is found."
(check-arg procedure? pred find)
(let loop ((lst lst))
(and (not (null? lst))
(let ((head (car lst)))
(if (pred head)
lst
(loop (cdr lst)))))))
(define (take-while pred ls)
"Return a new list which is the longest initial prefix of LS whose
elements all satisfy the predicate PRED."