Ruby Factorial

#!/usr/local/bin/ruby -wKU # encoding: utf-8 # factorial # 10.fact class Integer   def !     if self <= 1       1     else       self * (self-1).!     end   end   def fact     (1..self).inject(:*)   end   def fact_inside     "#{(1..self).to_a.reverse.join('×')} = #{self.fact}"        end   def progress     (1..self).inject(:+)   end end p 10.! p 10.fact_inside p 10.progress