ruby/ruby — pull request #644 by simonbaird (2014-06-28 08:33:41+00:00)
Title: Define the TAU circle constant [Feature #4897]

* Define TAU constant in math.c similar to PI.

* Define TAU method in bigdecimal/math based on existing
PI method.

* Minor change to error message about zero or negative precision in
BigMath.PI for clarity and consistency with other methods.