[英]Flex (lexical analyzer) not recognizing or operator
I have a problem with flex. 我对flex有问题。 It doesn't recognize the or operator in this rule:
它在此规则中无法识别or运算符:
[0-9A-Za-z]+{CORRECT} | {CORRECT}[0-9A-Za-z]+ [0-9A-Za-z]+{CORRECT}[0-9A-Za-z]+ {...}
If I split it into three rules then it is recognized: 如果我将其划分为三个规则,那么它将被识别:
[0-9A-Za-z]+{CORRECT} {...}
{CORRECT}[0-9A-Za-z]+ { ...}
[0-9A-Za-z]+{CORRECT}[0-9A-Za-z]+ {...}
To explain myself better the pattern I am trying to recognize is: 为了更好地说明自己,我尝试识别的模式是:
CORRECT [1-9]*_[1-9]*0
And in order for flex to recognize the CORRECT pattern only when it is not surrounded by other characters I have to add these three rules. 为了使flex仅在不被其他字符包围时才识别正确的模式,我必须添加这三个规则。
Full flex code: 完整的弹性代码:
%option noyywrap
%{
#include <stdio.h>
int num_lines=1;
%}
CORRECT [1-9]*_[1-9]*0
%%
{CORRECT} { printf("CORRECT TOKEN:%s\n",yytext); }
[0-9A-Za-z]+{CORRECT} { printf("ERROR %d:Unidentified symbol: %s\n",num_lines,yytext);}
{CORRECT}[0-9A-Za-z]+ { printf("ERROR %d:Unidentified symbol: %s \n",num_lines,yytext);}
[0-9A-Za-z]+{CORRECT}[0-9A-Za-z]+ { printf("ERROR %d:Unidentified symbol: %s \n",num_lines,yytext); }
"\n" { num_lines++; }
" "
"\t"
"\r"
. { printf("ERROR %d:Unidentified symbol: %s \n",num_lines,yytext);}
%%
int main(int argc,char **argv)
{
++argv,--argc;
if(argc>0)
yyin=fopen(argv[0],"r");
else
yyin=stdin;
yylex();
}
Whitespace is significant in a lex pattern. 空格在lex模式中很重要。
a | b
a | b
is not the same as a|b
. a | b
与a|b
。 In the troublesome pattern, you have whitespace that I don't think you intended. 在麻烦的模式中,您有空白,我认为您不是故意的。
That said, in my opinion, your 3-pattern solution is easier to read and maintain. 也就是说,我认为,您的3模式解决方案更易于阅读和维护。
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