我的ANTLR 4 Lexer.getCharPositionInLine的理解()函數是,它應該爲「在該令牌的第一個字符發生從零開始計數行內字符位置」返回--The定形的Antlr 4參考爲什麼antlr 4 Lexer.getCharPositionInLine()不正確地返回0?
使用以下antlr 4語法,似乎Lexer函數getCharPositionInLine()始終返回0.注意COMMENT詞法分析器規則中的Java代碼。它包含打印從getCharPositionInLine()返回的值的代碼。
grammar Expr;
compilUnit : stat+ EOF ;
stat : assign NEWLINE ;
assign : IDENT ASSIGN INT ;
// Lexer rules
ASSIGN : '=' {System.out.println(getLine() + ":" + getCharPositionInLine() + " /" + getText() + "/");} ;
APOS : '\'' {System.out.println(getLine() + ":" + getCharPositionInLine() + " /" + getText() + "/");} ;
INT : ('0' | '-'? [1-9][0-9]*) {System.out.println(getLine() + ":" + getCharPositionInLine() + " /" + getText() + "/");} ;
IDENT : [a-zA-Z][a-zA-Z0-9]* {System.out.println(getLine() + ":" + getCharPositionInLine() + " /" + getText() + "/");} ;
/* For lines that have only a comment preceeded by optional white space,
* skip the entire line including the newline. For lines that have a
* comment preceeded by other code skip the comment and return a
* NEWLINE. */
COMMENT : [ \t]* APOS NEND* END
{
int line = getLine();
int pos = getCharPositionInLine();
System.out.println("COMMENT " + line + ":" + pos + " /" + getText() + "/");
if (pos == 0) {
skip();
}
else {
setType(NEWLINE);
setText("\n");
}
}
;
NEWLINE : END+ {System.out.println(getLine() + ":" + getCharPositionInLine() + " /" + getText() + "/");} ;
WS : [ \t]+ {System.out.println(getLine() + ":" + getCharPositionInLine() + " /" + getText() + "/"); skip();} ;
fragment END : '\u000c'? '\r'? '\n' ;
fragment NEND : ~[\u000c\r\n] ;
我使用這三個命令,在命令行:
java -jar antlr/antlr-4.1-complete.jar Expr.g4
javac -cp antlr/antlr-4.1-complete.jar Expr*.java
java -cp "antlr/antlr-4.1-complete.jar;." org.antlr.v4.runtime.misc.TestRig Expr compilUnit -tokens progs/hello.laf
與此輸入:
'Yo
x = 3 'Yay
我得到這樣的輸出:
COMMENT 2:0 /'Yo
/
2:1 /x/
2:2//
2:3 /=/
2:4//
2:5 /3/
COMMENT 3:0/'Yay
/
[@0,4:4='x',<4>,2:0]
[@1,6:6='=',<1>,2:2]
[@2,8:8='3',<3>,2:4]
[@3,16:15='<EOF>',<-1>,3:0]
line 3:0 missing NEWLINE at '<EOF>'
看樣子那是因爲評論詞法分析器r ule包括匹配一個換行符,詞法分析器已經將行號加1,並將字符位置重置爲0.但是,這與「The Definitive Antlr 4 Reference」中的文檔不符。我究竟做錯了什麼?或者這是Antlr 4中的一個錯誤?