Reverse Polish Notation Calc by Ruby

rpncalc.rb

#!/usr/bin/env ruby
# encoding : utf-8

# Complexクラスは1.9.xでは組み込みクラスになった
# require 'complex'
include Math

ONE_ARG_FUNCS = %w(sin cos tan asin acos atan sinh cosh tanh asinh acosh atanh exp log log10 log2 sqrt)

stack = []
continue = true
fold_mode = false
while continue == true
  gets.chomp.split.each do |input|

    # 引数一個の数学関数
    if ONE_ARG_FUNCS.member?(input)
      stack.push(send(input, stack.pop))
      # eval("stack.push(#{input}(stack.pop))")
      next
    end

    # fold
    if fold_mode == true
      case input
      when '+', '-', '*', '/', '**', '^'

        # 初期値の設定
        case input
        when '+', '-'
          init = 0
        when '*', '/'
          init = 1
        when '**', '^'
          init = stack.pop
          input = '**'
        end

        until stack.empty?
          eval("init #{input}= stack.pop")
        end
        stack.push(init)
      end

      fold_mode = false
      next
    end

    case input
    when /^[\+|\-]?\d+$/
      stack.push(input.to_i)
    when /^[\+|\-]?\d+\.\d*$/
      stack.push(input.to_f)
    when /^[\+\-]?\d*\.?\d*[\+\-]?\d*\.?\d*i$/
      stack.push(input.to_c)
    when 'PI'
      stack.push(PI)
    when 'E'
      stack.push(E)
    when 'I'
      stack.push(Complex::I)
    when '+'
      stack.push(stack.pop + stack.pop)
    when '-'
      stack.push(stack.pop - stack.pop)
    when '*'
      stack.push(stack.pop * stack.pop)
    when '/'
      stack.push(stack.pop / stack.pop)
    when '%'
      stack.push(stack.pop % stack.pop)
    when '**', '^'
      stack.push(stack.pop ** stack.pop)
    when 'abs'
      stack.push((stack.pop).abs)

    when 'inverse'
      stack.reverse!
    when 'fold', 'inject'
      fold_mode = true

    # スタックの一番頭の要素をpop（削除）
    when 'pop'
      stack.pop

    when 'exit', 'q', 'quit', 'bye'
      continue = false
    end
  end
    p stack
end