docs: function(regexp, type){
      var captures;
      if (captures = regexp.exec(this.input)) {
        var len = captures[0].length;
        var val = captures[1];
        var diff = len - (val ? val.length : 0);
        var tok = this.tok(type, val);
        this.consume(len);
        this.incrementColumn(diff);
        return tok;
      }
    }