GNU bug report logs - #17485
(srfi srfi-1) reduce-right does not scale, version 2.0.9

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From: Mark H Weaver <mhw <at> netris.org>
To: David Kastrup <dak <at> gnu.org>
Cc: 17485 <at> debbugs.gnu.org
Subject: bug#17485: [PATCH 3/3] Reimplement reduce-right in srfi-1
Date: Tue, 03 Jun 2014 23:30:25 -0400

David Kastrup <dak <at> 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 <at> 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

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