code: function(type) {
        if (~keywords.indexOf(type)) {
          return this;
        }
        var stack = [];
        keywords.push(type);
        regInvalid = true;
        map[type] = {
          wrap: function(value) {
            return this.ld + slice.call(arguments, 0).join(delim) + this.rd;
          }
        };
  
        // 定义map.ld
        Object.defineProperty(map[type], 'ld', {
          get: function() {
            var depth = stack.length;
            stack.push(depth);
            return delim + type + depth + delim;
          }
        });
  
        // 定义map.rd
        Object.defineProperty(map[type], 'rd', {
          get: function() {
            return delim + stack.pop() + type + delim;
          }
        });
      }
docs: 添加其他中间码类型。
  @param {String} type 类型
  @function add
  @memberOf fis.compile.lang