Exclamation Factorial

exclamation.rb

require "mathn"
class Integer
  def !
    (1..self).inject(:*)
  end
end

f1 = ->a,b,c{  a - b  / c }
f2 = ->a,b,c{ (a - b) / c }

pp = ->abc{
  print "(%i - %i) / %i = %i\n"         % [*abc, f2[*abc]]
  print " %i - %i  / %i = %i! = %i\n\n" % [*abc, f2[*abc], f1[*abc]]
}

[*2..1000].repeated_permutation(3)
          .select { |abc| f1[*abc] == f2[*abc].! }
          .each { |abc| pp[abc] }