From de99fc7a0c67d8193d693fec1d7a32dd2713b2f8 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Wed, 27 Aug 2014 17:49:04 -0400
Subject: signal: Add signal-negate.

* sly/signal.scm (signal-negate): New procedure.
---
 sly/signal.scm | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sly/signal.scm b/sly/signal.scm
index 8ecc58d..543f4d0 100644
--- a/sly/signal.scm
+++ b/sly/signal.scm
@@ -39,6 +39,7 @@
             signal-merge
             signal-zip
             signal-map
+            signal-negate
             signal-fold
             signal-filter
             signal-reject
@@ -226,6 +227,11 @@ or more SIGNALS."
                          (%signal-set! self (current-value)))
                        inputs)))
 
+(define (signal-negate signal)
+  "Create a new signal whose value is the 'not' of the value of
+SIGNAL."
+  (signal-map not signal))
+
 (define (signal-fold proc init signal . rest)
   "Create a new signal that applies PROC to the values stored in
 SIGNAL. PROC is applied with the current value of SIGNAL and the
-- 
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