parsing - 如何使用 BNFC 定义 INI 文件语法？

Question

http://www.cs.chalmers.se/Cs/Research/Language-technology/BNFC/

我应该如何编写带标签的 BNF 以让 BNFC 为我生成 INI 解析器？

我只到了这么远o__O!

entrypoints File ;

comment "#" ;

token ID ( letter | digit | ["-_'"] )+ ;

Ini. File ::= [Section] ;
Sect. Section ::= "[" ID "]" [Statement] ;
Bind. Statement ::= ID "=" ID ;

separator Statement "\n" ;
terminator Section "" ;

[name]
#x = 10
y = 20

Parse Successful!

[Abstract Syntax]

Ini [Sect (ID "name") [Bind (ID "y") (ID "20")]]

[Linearized tree]

[name]y = 20

[name]
x = 10
#y = 20

Parse Successful!

[Abstract Syntax]

Ini [Sect (ID "name") [Bind (ID "x") (ID "10")]]

[Linearized tree]

[name]x = 10

o__O我被困住了......

Answer 1

我询问了一位 BNFC 开发人员并在此引用他的回复:

Space characters such as newlines are not well supported in tokens, because BNFC has a hard-wired lexer type "space". The idea is that spaces can't carry meaning in "well-behaved" languages. One of those restrictions that has made BNFC so simple... but you should be able solve this by using a preprocessor, e.g. parse input line by line.

例如:

entrypoints File ;

comment "#" ;

token ID ( letter | digit | ["-_'"] )+ ;

Ini. File ::= [Section] ;
Sect. Section ::= "[" ID "]" [Statement] ;
Bind. Statement ::= ID "=" ID ;

separator Statement "//" ;
terminator Section "//" ;

读:

[name]
x = 10
y = 20

预处理:

[name]//
x = 10//
y = 20//

解析:

Ini [Sect (ID "name") [Bind (ID "x") (ID "10"), Bind (ID "y") (ID "20")]]

转换:

                                          ↓                       ↓
Ini [Sect (ID "name") [Bind (ID "x") (ID "0"), Bind (ID "y") (ID "0")]]

写:

[name]//
x = 0//
y = 0//

后期处理:

[name]
x = 0
y = 0

(没查过，不知道有没有用，只是给个思路!!)