From c68106172e7115ec1f69538d757144df8ca70b7b Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Wed, 8 Apr 2020 17:01:16 -0400
Subject: math: Add 2pi variable.

* chickadee/math.scm (2pi): New variable.
---
 chickadee/math.scm | 2 ++
 doc/api.texi       | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/chickadee/math.scm b/chickadee/math.scm
index 050dac1..b970526 100644
--- a/chickadee/math.scm
+++ b/chickadee/math.scm
@@ -18,6 +18,7 @@
 (define-module (chickadee math)
   #:export (pi
             pi/2
+            2pi
             cotan
             square
             clamp
@@ -30,6 +31,7 @@
 
 (define pi 3.14159265358979323846)
 (define pi/2 (/ pi 2.0))
+(define 2pi (* pi 2.0))
 
 (define-inlinable (cotan z)
   "Return the cotangent of Z."
diff --git a/doc/api.texi b/doc/api.texi
index f553f25..3992c06 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -571,6 +571,10 @@ approximation that is ``good enough.''
 Half of @var{pi}.
 @end defvar
 
+@defvar 2pi
+Twice @var{pi}.
+@end defvar
+
 @deffn {Procedure} cotan z
 Return the cotangent of @var{z}.
 @end deffn
-- 
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