Merge pull request #17 from FranklinChen/add-tau

Add tau.

Author: paf31

src/Math.js

@@ -74,6 +74,8 @@ exports.log10e = Math.LOG10E;
 
 exports.pi = Math.PI;
 
+exports.tau = 2 * Math.PI;
+
 exports.sqrt1_2 = Math.SQRT1_2;
 
 exports.sqrt2 = Math.SQRT2;

src/Math.purs

@@ -87,6 +87,9 @@ foreign import log10e :: Number
 -- | The ratio of the circumference of a circle to its diameter, around 3.14159.
 foreign import pi :: Number
 
+-- | The ratio of the circumference of a circle to its radius, around 6.283185.
+foreign import tau :: Number
+
 -- | The Square root of one half, around 0.707107.
 foreign import sqrt1_2 :: Number