Playing around with calculating π

pi.rb

# Using a simple Gregory-Leibniz series we can calculate π
# to, theoretically, any degree of accuracy. The series converges very
# slowly however, so it'll take 500,000 iterations to get the first five
# digits of π.
#
# This series can be expressed algebraically like so:
#
#  ∞
#  Σ  (-1)^i * ( 4 / 2i + 1 )
# i=0
#

i = 0
pi = 0

while true
  term = Rational(4, ((2 * i) + 1))

  pi += (((-1) ** i) * term)

  print "π = #{pi.to_f}\r"
  $stdout.flush

  i += 1 
end