Question

我的lex文件文件中出现以下错误我不知道为什么会发生这种错误关于返回解析器的每个标记

      lexical.l: In function âyylexâ:
lexical.l:29: error: expected expression before â;â token
lexical.l:30: error: âCALLâ undeclared (first use in this function)
lexical.l:30: error: (Each undeclared identifier is reported only once
lexical.l:30: error: for each function it appears in.)
lexical.l:31: error: âIDâ undeclared (first use in this function)
lexical.l:32: error: âNUMâ undeclared (first use in this function)
lexical.l:36: error: âRELOPâ undeclared (first use in this function)
lexical.l:37: error: âADDOPâ undeclared (first use in this function)
lexical.l:38: error: âMULOPâ undeclared (first use in this function)
lexical.l:39: error: âASSIGNâ undeclared (first use in this function)
lexical.l:40: error: âANDâ undeclared (first use in this function)
lexical.l:41: error: âORâ undeclared (first use in this function)
lexical.l:42: error: âNOTâ undeclared (first use in this function)

这是我的lex文件，用于将令牌发送到解析器

%{
#include <stdio.h>
#include"bison.tab.h"
void showToken(char*);
%}

%option yylineno
%option noyywrap
digit [0-9]
letter [a-zA-Z]
whitespace [ \t]

%%
"else"                      {return ELSE;}
"real"                      {return REAL;}
"integer"                   {return INTEGER;}
"write"                     {return XWRITE;}
"while"                     {return WHILE;}
"end"                       {return END;}
"do"                        {return DO;}
"if"                        {return IF;}
"then"                      {return THEN;}
"program"                   {return XPROGRAM;}
"function"                  {return FUNCTION;}
"return"                    {return XRETURN;}
"read"                      {return XREAD;}
"var"                       {return VAR;}
"for"                       {return FOR;}
"begin"                     {return BEGIN;}
"call"                      {return CALL;}
{letter}({letter}|{digit})*         {return ID;}
{digit}{digit}*(("."{digit}{digit}*)?)      {return NUM;}
{digit}{digit}*({letter}|{digit})*      printf("Lexical Error");
[(),:;.]                return yytext[0]; 
^[\t ]+                 ;
(==|<>|<|<=|>|>=)           {return RELOP;}
(\+|-)                  {return ADDOP;}
(\*|\/)                 {return MULOP;}
(=)                 {return ASSIGN;}
(&&)                    {return AND;}
(\|\|)                  {return OR;}
(!)                 {return NOT;}
{whitespace}+               ;
"/*".*"*/"              ;
.                   {   
                    printf("Lexical Error");
                    exit(0);
                    }

%%
void showToken(char* name){
    printf("<%s,%s>",name,yytext);
}

如果返回的代币是大写字母还是无关紧要？我应该在这里包含解析器文件还是只包含tab.c文件？

Answer 1

您不能使用名称BEGIN作为令牌名称，因为BEGIN已经#define作为flex的其他内容。我不知道为什么会产生第一个错误（第29行），但你应该先尝试修复它，如果没有帮助，请粘贴bison.tab.h。

Answer 2

错误告诉您，您尝试返回的各种令牌（CALL，ID，NUM，RELOP等）尚未定义。您要包含bison.tab.h文件，这意味着您在%token文件中缺少.y这些令牌的声明。

野牛解析器错误

2 个答案: