Could the following make its way into unstable/list? It adds remf for
symmetry with findf and memf.
David
>From 15ed53550163a652d02b71eb1145db2da83f75a2 Mon Sep 17 00:00:00 2001
From: dvanhorn <dvanh...@ccs.neu.edu>
Date: Tue, 25 May 2010 20:24:21 -0400
Subject: [PATCH] Added remf to unstable/list.
---
collects/tests/unstable/list.rkt | 9 +++++++++
collects/unstable/list.rkt | 10 ++++++++++
collects/unstable/scribblings/list.scrbl | 15 +++++++++++++++
3 files changed, 34 insertions(+), 0 deletions(-)
create mode 100644 collects/tests/unstable/list.rkt
diff --git a/collects/tests/unstable/list.rkt b/collects/tests/unstable/list.rkt
new file mode 100644
index 0000000..fedd410
--- /dev/null
+++ b/collects/tests/unstable/list.rkt
@@ -0,0 +1,9 @@
+#lang scheme
+(require unstable/list)
+(require tests/eli-tester)
+(test
+ (remf positive? '()) => '()
+ (remf positive? '(1 -2 3 4 -5)) => '(-2 3 4 -5)
+ (remf even? '(1 -2 3 4 -5)) => '(1 3 4 -5)
+ (remf (λ (x) #f) '(1 -2 3 4 -5)) => '(1 -2 3 4 -5))
+
diff --git a/collects/unstable/list.rkt b/collects/unstable/list.rkt
index ab35a6f..f8b964d 100644
--- a/collects/unstable/list.rkt
+++ b/collects/unstable/list.rkt
@@ -112,3 +112,13 @@
(provide map/values)
+;; dvanhorn added:
+
+(define (remf f ls)
+ (cond [(null? ls) '()]
+ [(f (car ls)) (cdr ls)]
+ [else
+ (cons (car ls)
+ (remf f (cdr ls)))]))
+
+(provide/contract [remf (-> procedure? list? list?)])
diff --git a/collects/unstable/scribblings/list.scrbl
b/collects/unstable/scribblings/list.scrbl
index 76509f6..3bc0a26 100644
--- a/collects/unstable/scribblings/list.scrbl
+++ b/collects/unstable/scribblings/list.scrbl
@@ -103,3 +103,18 @@ Produces lists of the respective values of @racket[f]
applied to the elements in
}
+...@addition{david Van Horn}
+
+...@defproc[(remf [pred procedure?]
+ [lst list?])
+ list?]{
+Returns a list that is like @racket[lst], omitting the first element of
@racket[lst]
+for which @racket[pred] produces a true value.
+
+...@defexamples[
+#:eval the-eval
+(remf negative? '(1 -2 3 4 -5))
+]
+
+}
+
--
1.7.1
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