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我试图让域名有限的语法工作。语法在http://tools.ietf.org/html/rfc1035的2.3.1节定义。它的一个子集是根据域名解析器的语法
<label> ::= <letter> [ [ <ldh-str> ] <let-dig> ]
<ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>
<let-dig-hyp> ::= <let-dig> | "-"
<let-dig> ::= <letter> | <digit>
<letter> ::= any one of the 52 alphabetic characters A through Z in upper case and a through z in lower case
<digit> ::= any one of the ten digits 0 through 9
我下面的尝试。我想匹配label
grammar Domain;
domain: label NEWLINE;
label: LETDIG (LETDIGHYP+ LETDIG)?;
LETDIGHYP : (LETDIG|'-');
LDHSTR : [0-9a-zA-Z-]+;
LETDIG : [0-9a-zA-Z];
NEWLINE : [\r\n]+ ;
不过,我得到一个line 1:0 mismatched input 'abc123' expecting LETDIG
试图对阵abc123
时。我的语法有什么问题?
谢谢