小编Man*_*nos的帖子

当我在以下文件上运行parser.y时,我收到以下错误:

myanalyzer.y: warning: 14 nonterminals useless in grammar
myanalyzer.y: warning: 36 rules useless in grammar
myanalyzer.y:7.8-18: fatal error: start symbol main_struct does not derive any sentence

我无法理解代码有什么问题:

    %{
    #include <stdio.h>
    #include <string.h>
    extern int line_num;
    extern char *yytext;
%}
%start main_struct

%left PLUS

%token PUBLIC   1
...         
%token CONSTANT_CHAR    45

%%
main_struct:variables_declaration
        class_declaration
        functions_declaration
        ;  

constant:   INT
        |BOOLEAN
        |CHAR
        |STRING
        |FLOAT
        |DOUBLE 
        ;

locality:   PUBLIC
        | PRIVATE
        ;

identifier1:    IDENTIFIER
        | identifier1 COMMA IDENTIFIER
        ;

class_body: /*empty*/
        |  locality variables_declaration …