From: Mark H Weaver <mhw@netris.org>
To: David Kastrup <dak@gnu.org>
Cc: 17485@debbugs.gnu.org
Subject: bug#17485: [PATCH 3/3] Reimplement reduce-right in srfi-1
Date: Tue, 03 Jun 2014 23:30:25 -0400 [thread overview]
Message-ID: <871tv5uzam.fsf@yeeloong.lan> (raw)
In-Reply-To: <1401821778-19972-3-git-send-email-dak@gnu.org> (David Kastrup's message of "Tue, 3 Jun 2014 20:56:18 +0200")
David Kastrup <dak@gnu.org> writes:
> * module/srfi/srfi-1.scm (reduce-right): Avoid use of drop-right in
> connection with last as a single upfront reverse is more efficient and
> simpler to understand.
>
> Signed-off-by: David Kastrup <dak@gnu.org>
> ---
> module/srfi/srfi-1.scm | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/module/srfi/srfi-1.scm b/module/srfi/srfi-1.scm
> index 73d164a..6aa249a 100644
> --- a/module/srfi/srfi-1.scm
> +++ b/module/srfi/srfi-1.scm
> @@ -573,10 +573,7 @@ then that's the return value."
> F is on two elements from LST, rather than one element and a given
> initial value. If LST is empty, RIDENTITY is returned. If LST
> has just one element then that's the return value."
> - (check-arg procedure? f reduce)
> - (if (null? lst)
> - ridentity
> - (fold-right f (last lst) (drop-right lst 1))))
> + (reduce f ridentity (reverse lst)))
>
> (define map
> (case-lambda
Looks good to me.
Mark
next prev parent reply other threads:[~2014-06-04 3:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-13 10:47 bug#17485: (srfi srfi-1) reduce-right does not scale, version 2.0.9 David Kastrup
2014-06-01 23:41 ` Mark H Weaver
2014-06-02 7:59 ` David Kastrup
2014-06-03 18:56 ` bug#17485: [PATCH 1/3] Let length+ return the length of dotted lists rather than #f David Kastrup
2014-06-03 18:56 ` bug#17485: [PATCH 2/3] Rewrite take-right, drop-right, drop-right! David Kastrup
2014-06-04 3:29 ` Mark H Weaver
2014-06-04 3:45 ` Mark H Weaver
2014-09-20 14:56 ` Mark H Weaver
2014-09-20 15:15 ` David Kastrup
2014-09-22 17:15 ` Mark H Weaver
2014-09-22 18:40 ` David Kastrup
2014-06-03 18:56 ` bug#17485: [PATCH 3/3] Reimplement reduce-right in srfi-1 David Kastrup
2014-06-04 3:30 ` Mark H Weaver [this message]
2014-06-04 3:42 ` bug#17485: [PATCH 1/3] Let length+ return the length of dotted lists rather than #f Mark H Weaver
2014-06-04 4:57 ` David Kastrup
2014-06-04 10:09 ` David Kastrup
2014-06-05 13:57 ` David Kastrup
2016-06-21 14:42 ` bug#17485: (srfi srfi-1) reduce-right does not scale, version 2.0.9 Andy Wingo
2016-06-21 15:31 ` David Kastrup
2016-07-12 7:07 ` Andy Wingo
2016-07-12 7:43 ` bug#17485: Ugh, well David Kastrup
2016-07-12 13:54 ` Andy Wingo
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