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srfi-1: Rewrite 'find' in Scheme.

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This halves the wall-clock time of:

  guile -c '(use-modules (srfi srfi-1)) (define lst (make-list 100000000 1)) (find zero? lst)'

and yields an 18% speedup on:

  guile -c '(use-modules (srfi srfi-1)) (define lst (make-list 100000000 1)) (find (lambda (x) (= 2 x)) lst)'

* libguile/srfi-1.c (scm_srfi1_find): Remove.
* libguile/srfi-1.h (scm_srfi1_find): Likewise.
* module/srfi/srfi-1.scm (find): New procedure.
* doc/ref/srfi-modules.texi (SRFI-1 Searching): Adjust docstring.
This commit is contained in:
Ludovic Courtès 2020-06-17 16:59:50 +02:00
parent 2e2e13c40a
commit 0360843ace
4 changed files with 16 additions and 29 deletions
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4
doc/ref/srfi-modules.texi
View file

@ -1,6 +1,6 @@
@c -*-texinfo-*-
@c This is part of the GNU Guile Reference Manual.
@c Copyright (C) 1996, 1997, 2000-2004, 2006, 2007-2014, 2017, 2018, 2019
@c Copyright (C) 1996, 1997, 2000-2004, 2006, 2007-2014, 2017, 2018, 2019, 2020
@c Free Software Foundation, Inc.
@c See the file guile.texi for copying conditions.
@ -824,7 +824,7 @@ predicate or a comparison object for determining which elements are to
be searched.
@deffn {Scheme Procedure} find pred lst
Return the first element of @var{lst} which satisfies the predicate
Return the first element of @var{lst} that satisfies the predicate
@var{pred} and @code{#f} if no such element is found.
@end deffn

25
libguile/srfi-1.c
View file

@ -1,6 +1,6 @@
/* srfi-1.c --- SRFI-1 procedures for Guile
Copyright 1995-1997,2000-2003,2005-2006,2008-2011,2013-2014,2018
Copyright 1995-1997,2000-2003,2005-2006,2008-2011,2013-2014,2018,2020
Free Software Foundation, Inc.
This file is part of Guile.
@ -575,29 +575,6 @@ SCM_DEFINE (scm_srfi1_delete_duplicates_x, "delete-duplicates!", 1, 1, 0,
}
#undef FUNC_NAME
SCM_DEFINE (scm_srfi1_find, "find", 2, 0, 0,
(SCM pred, SCM lst),
"Return the first element of @var{lst} which satisfies the\n"
"predicate @var{pred}, or return @code{#f} if no such element is\n"
"found.")
#define FUNC_NAME s_scm_srfi1_find
{
SCM_VALIDATE_PROC (SCM_ARG1, pred);
for ( ; scm_is_pair (lst); lst = SCM_CDR (lst))
{
SCM elem = SCM_CAR (lst);
if (scm_is_true (scm_call_1 (pred, elem)))
return elem;
}
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_find_tail, "find-tail", 2, 0, 0,
(SCM pred, SCM lst),
"Return the first pair of @var{lst} whose @sc{car} satisfies the\n"

3
libguile/srfi-1.h
View file

@ -1,5 +1,5 @@
/* srfi-1.h --- SRFI-1 procedures for Guile
Copyright 2002-2003,2005-2006,2010-2011,2018
Copyright 2002-2003,2005-2006,2010-2011,2018,2020
Free Software Foundation, Inc.
This file is part of Guile.
@ -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 (SCM pred, SCM lst);
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);

13
module/srfi/srfi-1.scm
View file

@ -1,6 +1,6 @@
;;; srfi-1.scm --- List Library
;; Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2010, 2011, 2014 Free Software Foundation, Inc.
;; Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2009, 2010, 2011, 2014, 2020 Free Software Foundation, Inc.
;;
;; This library is free software; you can redistribute it and/or
;; modify it under the terms of the GNU Lesser General Public
@ -720,6 +720,17 @@ the list returned."
;;; Searching
(define (find pred lst)
"Return the first element of @var{lst} that 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)
head
(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."