Function is_id

js/SCAST.js:64–66

(ch)

            return /[a-zA-Z$_]/i.test(ch);
        }
        function is_id(ch) {
            return is_id_start(ch) || "0123456789".indexOf(ch) >= 0;
        }
        function is_op_char(ch) {
            return "+-*/%=&|<>!^\\".indexOf(ch) >= 0;// \ for 正则
        }