From 8ac70ff3cef2963c460ce5382e37946eb0a4914e Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Mon, 9 Mar 2015 08:46:43 -0400
Subject: signals: Add signal-timer.

* sly/signal.scm (signal-timer): New procedure.
* doc/api/signals.texi: Document it.
---
 doc/api/signals.texi | 5 +++++
 sly/signal.scm       | 7 ++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/doc/api/signals.texi b/doc/api/signals.texi
index a4e2c01..9f674e1 100644
--- a/doc/api/signals.texi
+++ b/doc/api/signals.texi
@@ -191,6 +191,11 @@ Create a new signal that takes on the value of @var{signal} every
 Create a new signal that emits @var{step} every @var{step} ticks.
 @end deffn
 
+@deffn {Scheme Procedure} signal-timer [@var{step}]
+Create a new signal that emits the total time elapsed since its
+creation every @var{step} (1 by default) ticks.
+@end deffn
+
 @deffn {Scheme Procedure} signal-since @var{step} @var{signal}
 Create a new signal that emits the time since @var{signal} was updated
 ever @var{step} ticks.
diff --git a/sly/signal.scm b/sly/signal.scm
index 788bb25..83f1ea5 100644
--- a/sly/signal.scm
+++ b/sly/signal.scm
@@ -50,7 +50,7 @@
             signal-tap
             signal-timestamp signal-time
             signal-sample
-            signal-every signal-since
+            signal-every signal-timer signal-since
             signal-delay
             signal-throttle
             signal-generator))
@@ -366,6 +366,11 @@ ticks."
   "Create a new signal that emits STEP every STEP ticks."
   (signal-sample step (make-signal step)))
 
+(define* (signal-timer #:optional (step 1))
+  "Create a new signal that emits the total time elapsed since its
+creation every STEP ticks."
+  (signal-fold + 0 (signal-every step)))
+
 (define (signal-since step signal)
   "Create a new signal that emits the time since SIGNAL was updated
 every STEP ticks."
-- 
cgit v1.2.3