From: Chris Hanson <org/chris-hanson/cph>
Date: Fri, 23 Dec 2005 04:15:45 +0000 (+0000)
Subject: Implement FIND-UNIQUE-MATCHING-ITEM and FIND-UNIQUE-NON-MATCHING-ITEM.
X-Git-Tag: 20090517-FFI~1148
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=1e15f4c3c85f5d128e5d9d8fbe07553b9b9afef1;p=mit-scheme.git

Implement FIND-UNIQUE-MATCHING-ITEM and FIND-UNIQUE-NON-MATCHING-ITEM.
---

diff --git a/v7/src/runtime/list.scm b/v7/src/runtime/list.scm
index 7867e17d9..c7593a602 100644
--- a/v7/src/runtime/list.scm
+++ b/v7/src/runtime/list.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: list.scm,v 14.49 2005/04/28 04:33:36 cph Exp $
+$Id: list.scm,v 14.50 2005/12/23 04:15:38 cph Exp $
 
 Copyright 1986,1987,1988,1989,1990,1991 Massachusetts Institute of Technology
 Copyright 1992,1993,1994,1995,1996,2000 Massachusetts Institute of Technology
@@ -691,6 +691,32 @@ USA.
 	      (error:not-list items 'FIND-MATCHING-ITEM))
 	  #f))))
 
+(define (find-unique-matching-item items predicate)
+  (let loop ((items* items))
+    (if (pair? items*)
+	(if (predicate (car items*))
+	    (if (there-exists? (cdr items*) predicate)
+		#f
+		(car items*))
+	    (loop (cdr items*)))
+	(begin
+	  (if (not (null? items*))
+	      (error:not-list items 'FIND-UNIQUE-MATCHING-ITEM))
+	  #f))))
+
+(define (find-unique-non-matching-item items predicate)
+  (let loop ((items* items))
+    (if (pair? items*)
+	(if (predicate (car items*))
+	    (loop (cdr items*))
+	    (if (for-all? (cdr items*) predicate)
+		(car items*)
+		#f))
+	(begin
+	  (if (not (null? items*))
+	      (error:not-list items 'FIND-UNIQUE-NON-MATCHING-ITEM))
+	  #f))))
+
 (define (count-matching-items items predicate)
   (do ((items* items (cdr items*))
        (n 0 (if (predicate (car items*)) (+ n 1) n)))
diff --git a/v7/src/runtime/runtime.pkg b/v7/src/runtime/runtime.pkg
index d27a093b5..b1a743cfb 100644
--- a/v7/src/runtime/runtime.pkg
+++ b/v7/src/runtime/runtime.pkg
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: runtime.pkg,v 14.569 2005/12/18 00:20:43 cph Exp $
+$Id: runtime.pkg,v 14.570 2005/12/23 04:15:45 cph Exp $
 
 Copyright 1988,1989,1990,1991,1992,1993 Massachusetts Institute of Technology
 Copyright 1994,1995,1996,1997,1998,1999 Massachusetts Institute of Technology
@@ -2164,6 +2164,8 @@ USA.
 	  fifth
 	  find-matching-item
 	  find-non-matching-item
+	  find-unique-matching-item
+	  find-unique-non-matching-item
 	  first
 	  fold-left
 	  fold-right