syntax.ebnf

(* Copyright 2023 SJTU X-Lance Lab
   
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at
   
       http://www.apache.org/licenses/LICENSE-2.0
   
   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

   Created by Danyang Zhang @X-Lance.
*)

slot = "<" [ modifier { "," modifier } ":" ] identifier ">" ;

modifier = ( list-modifier
           | regex-modifier
           | url-modifier
           | common-modifier
           | other-modifier
           | "no_quote"
           ) , [ "'" ] ;
(* "'"指该修饰器应应用于列表每个元素上
   "no_quote"是保留关键字，应用作最后的修饰词，表示该串不需要对引号等自动转义
   多个修饰符按从右到左的顺序依次作用
*)

list-modifier = "to_list"
              | "regex_list" ;
regex-modifier = "regex_esc" ;
url-modifier = "url_path"
             | "url_query"
             | "url_title" ;
common-modifier = "lower"
                | "upper" ;
other-modifier = "filter_comma"
               | "remove_howto" ;

identifier = ( alphadigit-symbol | "_" ), { alphadigit-symbol | "_" } ;