From 90addf3281a3df6b2e249ea124d68dff9bdb9727 Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Sun, 7 Mar 2021 09:15:14 +0100
Subject: Add 'sinewave' effect

---
 guile/starlet/effects.scm | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

(limited to 'guile/starlet/effects.scm')

diff --git a/guile/starlet/effects.scm b/guile/starlet/effects.scm
index d908a52..73b19eb 100644
--- a/guile/starlet/effects.scm
+++ b/guile/starlet/effects.scm
@@ -1,6 +1,7 @@
 (define-module (starlet effects)
   #:use-module (starlet base)
-  #:export (flash))
+  #:export (flash
+             sinewave))
 
 
 (define pi (* 2 (acos 0)))
@@ -14,3 +15,10 @@
 (define (flash hz)
   (lambda (time)
     (square-wave time hz)))
+
+
+(define (sinewave hz range-min range-max)
+  (lambda (time)
+    (+ range-min
+       (* (/ (- range-max range-min) 2)
+          (+ 1 (sin (* 2 pi hz time)))))))
-- 
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