再挑戦四則演算

arith_4.rb

# -*- coding:utf-8 -*-

Inf = 1.0 / 0

class Operator
  def initialize(a, b)
    @left = a
    @right = b
  end
  attr_reader :left, :right
end

class Calculator
  def initialize(c)
    @fomula = c
    @result = calc(c)
  end

  def calc(c)
    case c
    when Plus
      return calc(c.left) + calc(c.right)
    when Minus
      return calc(c.left) - calc(c.right)
    when Mul
      return calc(c.left) * calc(c.right)
    when Div
      begin
        calc(c.left) / calc(c.right)
      rescue
        return Inf
      end
    else
      return c.to_f
    end
  end

  def to_s
    def s(c)
      case c
      when Plus
        return "(" + s(c.left) + "+" + s(c.right) + ")"
      when Minus
        return "(" + s(c.left) + "-" + s(c.right) + ")"
      when Mul
        return "(" + s(c.left) + "*" + s(c.right) + ")"
      when Div
        return "(" + s(c.left) + "/" + s(c.right) + ")"
      else
        c.to_s
      end
    end
    return s(@fomula)
  end

  attr_reader :result
end

class Plus < Operator
end

class Minus < Operator
end

class Mul < Operator
end

class Div < Operator
end

def get_numbers(arg)
  s = :a
  e = s
  (arg.length - 1).times{e = e.succ}
  a = (s..e).to_a

  ret =  a.repeated_permutation(arg.length).to_a.map(&:uniq).map{|i| if i.length == arg.length then i end}.compact
  ret.each do |unit| # => [:a, :b, ...]
    a.each_with_index do |item, j|
      unit.map!{|k| if item == k then arg[j] else k end}
    end
  end
  return ret
end

def arith(*arg)
  results = []
  operators = [Plus, Minus, Mul, Div].repeated_permutation(3).to_a
  number_permutation = get_numbers(arg).uniq
  
  number_permutation.each do |i| # i => [a, b, c, d]
    a, b, c, d = i
    operators.each do |j| # j => 3 of [Plus, Minus, Mul, Div]
      s, t, u = j
      results << s.new(t.new(a, b), u.new(c, d))
      results << s.new(a, t.new(b, u.new(c, d)))
      results << s.new(t.new(u.new(a, b), c), d)
      results << s.new(t.new(a, u.new(b, c)), d)
      results << s.new(a, t.new(u.new(b, c), d))
    end
  end

  results.each_with_index do |item, index|
    calculator = Calculator.new(item)
    begin
      printf "%5d: %s = %.3f\n", index + 1, calculator.to_s, calculator.result
    rescue
      printf "%5d: %s = %s\n", index + 1, calculator.to_s, "Infinity"
    end
  end
end

def main
  return puts "error: use ruby version > 1.8.* " if RUBY_VERSION <= "1.8.7"
  return unless ARGV.length == 4
  a, b, c, d = ARGV.map{|i| i.to_i}
  arith(a, b, c, d)

  # test 1 あとで spec で書き直したいな
  c = Calculator.new(Plus.new(2, Plus.new(3, Minus.new(2, 1))))
  p c.result # => 6
  # test 2
  p c.to_s
end

if $0 == __FILE__
  main()
end