java ANTLR 4 $channel = 隐藏和选项
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ANTLR 4 $channel = HIDDEN and options
提问by user2055330
I need help with my ANTLR 4 grammar after deciding to switch to v4 from v3. I am not very experienced with ANTLR so I am really sorry if my question is dumb ;)
在决定从 v3 切换到 v4 后，我需要有关 ANTLR 4 语法的帮助。我对 ANTLR 不是很有经验，所以如果我的问题很愚蠢，我真的很抱歉；)
In v3 I used the following code to detect Java-style comments:
在 v3 中，我使用以下代码来检测 Java 风格的注释：
COMMENT
: '//' ~('\n'|'\r')* '\r'? '\n' {$channel=HIDDEN;}
| '/*' ( options {greedy=false;} : . )* '*/' {$channel=HIDDEN;}
;
In v4 there are no rule-specific options. The actions (move to hidden channel) are also invalid.
在 v4 中没有特定于规则的选项。动作（移动到隐藏频道）也无效。
Could somebody please give me a hint how to do it in ANTLR v4?
有人可以给我一个提示如何在 ANTLR v4 中做到这一点吗？
回答by Bart Kiers
The v4 equivalent would look like:
v4 等效项如下所示：
COMMENT
: ( '//' ~[\r\n]* '\r'? '\n'
| '/*' .*? '*/'
) -> channel(HIDDEN)
;
which will put all single- and multi line comment on the HIDDENchannel. However, if you're not doing anything with these HIDDEN-tokens, you could also skipthese tokens, which would look like this:
这会将所有单行和多行评论放在HIDDEN频道上。但是，如果您没有对这些HIDDEN-token做任何事情，您也可以使用skip这些令牌，如下所示：
COMMENT
: ( '//' ~[\r\n]* '\r'? '\n'
| '/*' .*? '*/'
) -> skip
;
Note that to tell the lexer or parser to match ungreedy, you don't use options {greedy=false;}anymore, but append a ?, similar to many regex implementations.
请注意，要告诉词法分析器或解析器匹配 ungreedy，您不再使用options {greedy=false;}，而是附加 a ?，类似于许多正则表达式实现。
