Implementation of pidigits using GMP

pidigits.rb

# The Computer Language Benchmarks Game
# http://shootout.alioth.debian.org/

# transliterated from Mario Pernici's Python program
# contributed by Rick Branson

require "rubygems"
require "gmp"

def gmpz(n)
  GMP::Z.new(n)
end

N = gmpz((ARGV[0] || 100).to_i)

i = k = ns = gmpz(0)
k1 = gmpz(1)
n,a,d,t,u = [1,0,1,0,0].map { |n| gmpz(n) }

g_zero  = gmpz(0)
g_one   = gmpz(1)
g_two   = gmpz(2)
g_three = gmpz(3)
g_ten   = gmpz(10)

loop do
  k += g_one
  t = n << g_one
  n *= k
  a += t
  k1 += g_two
  a *= k1
  d *= k1
  if a >= n
    q = (n*g_three +a)
    t = q.fdiv(d)
    u = q.fmod(d)
    u += n
    if d > u
      ns = ns * g_ten + t
      i += g_one
      if i % g_ten == g_zero
        puts "#{ns.to_s.rjust(10, '0')}\t:#{i.to_s}"
        ns = g_zero
      end
      break if i >= N
   
      a -= d * t
      a *= g_ten
      n *= g_ten
    end
  end
end