reduction.rb

#!/usr/bin/env ruby

if (ARGV.count != 2)
  puts 'Invalid number of arguments.'
  exit
end

a, b = ARGV.map { |s| s.to_i }

get_gcd = -> (m, n) do
  m, n = n, m if m < n
  return m if n == 0
  get_gcd[n, m % n]
end

gcd = get_gcd[a, b]

puts "#{a} : #{b} = #{a / gcd} : #{b / gcd}"