#!/usr/bin/ruby
#
## See: http://en.wikipedia.org/wiki/Machin-like_formula
#
# After 黃見利 (Hwang Chien-Lih) (1997)
say(
    4 * (
             (183 * atan2(1,     239)) +
             ( 32 * atan2(1,    1023)) -
             ( 68 * atan2(1,    5832)) +
             ( 12 * atan2(1,  110443)) -
             ( 12 * atan2(1, 4841182)) -
             (100 * atan2(1, 6826318))
        )
   );
say Num.pi;