signal: Add signal-negate.

* sly/signal.scm (signal-negate): New procedure.

1 files changed, 6 insertions, 0 deletions

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