class StrawpigScript
  attr_accessor :script

  TOKENS = ["+", "-", "*", "/", "x", "integer", "float"]


  def initialize(length)
    intermediate = length.times.inject("") {|program, i| program + " #{TOKENS.sample}"}
    with_ints = intermediate.gsub(/integer/) {rand(21)-10}
    @script = with_ints.gsub(/float/) {(rand*20.0-10.0).round(2)}
  end


  def evaluate(x)
      stack = []
      @script.split.each do |token|
        begin
          case token
          when /([-+]?[0-9]*\.?[0-9]+)/ # float
            stack.push($1.to_f)
          when /[-+]?[0-9]+/ # integer
            stack.push($1.to_i)
          when "+", "-", "*"
            raise ArgumentError, "short stack" if stack.length < 2
            arg1, arg2 = stack.pop(2)
            result = arg1.send(token.intern, arg2)
            stack.push(result)
          when "/"
            raise ArgumentError, "short stack" if stack.length < 2
            arg1, arg2 = stack.pop(2)
            result = (arg2 == 0) ? 0 : arg1.send(token.intern, arg2)
            stack.push(result)
          when "x"
            stack.push x
          else
            # ignore unrecognized tokens
          end
        rescue ArgumentError => e
          # don't pop items from the stack
        end
      end
      return stack[-1] || 1000000 # the top stack item, or a huge value if it's missing
  end
end