From b064377679c8e9cc702ab21db61b5f9024289900 Mon Sep 17 00:00:00 2001
From: Kevin Ryde <user42@zip.com.au>
Date: Fri, 11 Feb 2005 21:37:08 +0000
Subject: [PATCH] (reduce, reduce-right): Don't call f with ridentity, use it
 only if lst is empty, per srfi and intended optimization reduce represents
 over fold.

---
 srfi/srfi-1.scm | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/srfi/srfi-1.scm b/srfi/srfi-1.scm
index 1004cd51e..8d8a21d72 100644
--- a/srfi/srfi-1.scm
+++ b/srfi/srfi-1.scm
@@ -511,10 +511,14 @@
 	  (uf (g seed) (cons (f seed) lis))))))
 
 (define (reduce f ridentity lst)
-  (fold f ridentity lst))
+  (if (null? lst)
+      ridentity
+      (fold f (car lst) (cdr lst))))
 
 (define (reduce-right f ridentity lst)
-  (fold-right f ridentity lst))
+  (if (null? lst)
+      ridentity
+      (fold-right f (last lst) (drop-right lst 1))))
 
 
 ;; Internal helper procedure.  Map `f' over the single list `ls'.