Очень приятный язык.
https://github.com/ip1981/GCD/blob/mast
#!/usr/bin/env ruby
def gcd2 a, b
if b == 0
a
else
gcd2 b, a % b
end
end
# http://railspikes.com/2008/8/11/understanding-map-and-reduce
def gcdn ns
ns.reduce{ |a, b| gcd2 a, b }
end
puts gcdn ARGV.collect{ |s| s.to_i }
# ./gcd.rb 121 363 33 11