cal2.mirah

import java.util.HashMap

interface IOperator do
  def run(x:int, y:int)
    returns int
  end 
end

class Operators
  def add
    IOperator(@ops[:add])
  end
  
  def sub
    IOperator(@ops[:sub])
  end
  
  def add_op(name:string, op:IOperator)
      @ops ||= HashMap.new
      @ops[name] = op
  end
end

def calculate(op:IOperator)
  op.run(4, 20)
end

op = Operators.new

op.add_op :add { |x, y| x + y }
op.add_op :sub { |x, y| x - y }

puts calculate op.add

puts calculate op.sub