text: /**
   * 2017-09-16 Stanley Chen
   */
  
  var divide = function (x){
      return function (y) {
          return x / y ;
      };
  }; // This is "closure".
  
  var m = divide(2); // function(x),x = 2
  
  console.log(m(4)); // return 2 / y <--> function(y),y = 4
  
  
  var add = function(){
      return function(a,b){
          return a + b;
      };
  };
  
  var s = mu()(2,3); // *****
  console.log(s);