语法分析器显示成功使用flex和野牛 [英] Syntax analyser to show success using flex and bison

问题描述

我想让一个语法分析器识别一个有效的语句，并打印成功。但是，在制作lex和yacc文件后，我不断收到我的yacc文件中的错误，说：

I am trying to make a syntax analyzer that will recognize a valid statement and will print success upon doing so. However, after making the lex and yacc files, I keep getting errors in my yacc file which says:

在函数'yyparse'fofo。 y：在函数'yyparse'中：

fofo.y：13：5：error：stray'\223'in program

fofo.y：13：5：error： strady'\'in program

fofo.y：13：16：error：'n'undeclared（首次在此函数中使用）

fofo.y：13：16：注意：对于在
中出现的每个函数，每个未声明的标识符只报告一次。
fofo.y：13：18：error：expected'）'before'Invalid'

fofo.y ：13：18：错误：stray'\'in program

fofo.y：13：18：error：stray'\224'in program

In function 'yyparse'fofo.y: In function 'yyparse':
fofo.y:13:5: error: stray '\223' in program
fofo.y:13:5: error: stray '\' in program
fofo.y:13:16: error: 'n' undeclared (first use in this function)
fofo.y:13:16: note: each undeclared identifier is reported only once for each function it appears in
fofo.y:13:18: error: expected ')' before 'Invalid'
fofo.y:13:18: error: stray '\' in program
fofo.y:13:18: error: stray '\224' in program

这是我的yacc文件内容：

Here's my yacc file contents:

%{
#include <stdio.h>
%}

%start Stmt_list
%token Id Num Relop Addop Mulop Assignop Not

%%
Stmt_list   : Stmt ';' '\n' {printf ("\n Success. \n"); exit(0);}
        | Stmt_list Stmt ';' '\n'   {printf ("\n Success. \n"); exit(0);}
        | error '\n'    {printf ("\n Invalid. \n"); exit(1);}
        ;

Stmt    : Variable Assignop Expression
    ;

Variable    : Id 
        | Id '['Expression']'
        ;

Expression  : Simple_expression 
        | Simple_expression Relop Simple_expression
        ;

Simple_expression   : Term 
            | Simple_expression Addop Term
            ;

Term    : Factor 
    | Term Mulop Factor
    ;

Factor  : Id 
    | Num 
    | '('Expression')' 
    | Id '['Expression']' 
    | Not Factor
    ;

%%

#include"lex.yy.c"

int main()  
{   
    yyparse();  
    yylex();

}  

yyerror(char *s)  
{  
 printf("\nError\n");  
}  

推荐答案

文本中的非ASCII字符（可能来自粘贴Word文件中的文本），第13行，错误消息指示：

The errors come from having some non ASCII characters in the text (which probably come from pasting text from a Word file), on line 13, as the error message indicated:

        | error '\n'    {printf ("\n Invalid. \n"); exit(1);}
                                 ^              ^
                                 |              |
                                 `--------------`------------   The error is here!

请注意，引号字符不同于上面的行，应编辑为：

Note the quotation characters are different to the line above, and should be edited to be:

        | error '\n'    {printf ("\n Invalid. \n"); exit(1);}

我也在你的令牌周围添加了一些空白。例如，在这些行上：

I also added some white space around your tokens. For example, on these lines:

        | Id '['Expression']'
    | '('Expression')' 
    | Id '['Expression']'

，我改为：

        | Id '[' Expression ']'
    | '(' Expression ')' 
    | Id '[' Expression ']'

我也注意到你正在呼叫 C函数'exit'，但没有正确声明。您的标题中需要以下行：

I also note you are calling the C function 'exit' but have not declared it properly. You need the following line in your header:

#include <stdlib.h>

它似乎为我构建好了。

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