Associativity checker for well-known logical operations

assocchecker.rb

#!/usr/bin/env ruby

# assocchecker.rb : associativity checker for well-known logical operations
#   by takehikom

class AssociativityChecker
  def initialize
  end

  def and(*param)
    param.min
  end

  def or(*param)
    param.max
  end

  def xor(*param)
    param.inject {|result, item| result ^ item}
  end

  def nand(*param)
    1 - param.min
  end

  def nor(*param)
    1 - param.max
  end

  def start
    [:and, :or, :xor, :nand, :nor].each do |op|
      puts "[Truth table for #{op.to_s.upcase}]"
      check(op)
      puts
    end
  end

  def check(sym = :xor)
    flag_assoc = true

    puts "x|y|z|A|B|C|D|E"
    [0, 1].each do |x|
      [0, 1].each do |y|
        [0, 1].each do |z|
          x_y    = send(sym, x,   y)
          y_z    = send(sym, y,   z)
          x_y__z = send(sym, x_y, z)
          x__y_z = send(sym, x,   y_z)
          x_y_z  = send(sym, x,   y, z)
          puts [x, y, z, x_y, y_z, x_y__z, x__y_z, x_y_z].join("|")

          if x_y__z != x__y_z || x_y_z != x_y__z
            flag_assoc = false
          end
        end
      end
    end

    if $DEBUG
      puts "A := x op y"
      puts "B := y op z"
      puts "C := A op z"
      puts "D := x op B"
      puts "E := x op y op z"
    end

    if flag_assoc
      puts "This operation is associative."
    else
      puts "This operation is not associative."
    end
  end
end

if __FILE__ == $0
  AssociativityChecker.new.start
end