为什么当v立即在s之后的V位置时，程序上存在语法错误？ （lex yacc）

Question

LEX代码 ...

%option noyywrap
%{
    #include<stdio.h>
    #include"y.tab.h"
%}

%%
I|you|we|they|he|she|it                 return SUBJECT;
will                                    return AUX1;
did                                     return AUX2;
not                                     return NOT;
eat|drink|run|play                      return VERB1;
ate|drank|ran|played                    return VERB2;
\. return DOT;
\? return QUE;
%%

...

YACC代码 ...

%{
    #include<stdio.h>
    #include<stdlib.h>
    void yyerror(char *msg);
%}

%token  SUBJECT VERB1 DOT QUE VERB2 AUX1 AUX2 NOT

%% 
sentence:
    past DOT                {printf(" Sentence Approved "); exit(0);}
    | pastneg DOT           {printf(" Sentence Approved "); exit(0);}
    | pastint QUE           {printf(" Sentence Approved "); exit(0);}
    | fut DOT               {printf(" Sentence Approved "); exit(0);}
    | futneg DOT            {printf(" Sentence Approved "); exit(0);}
    | futint QUE            {printf(" Sentence Approved "); exit(0);}
    ;
present:
    s v          {printf(" Simple Present Tense");}
    ;
past:
    s p         {printf(" Simple Past Tense");}
    ;
pastneg:
    s x2 neg v  {printf(" Negative Simple Past Tense");}
    ;
pastint:
    x2 present  {printf(" Interrogative Simple Past Tense");}
    ;
fut:
    s x1 v      {printf(" Simple Future Tense");}
    ;
futneg:
    s x1 neg v  {printf(" Negative Simple Future Tense");}
    ;
futint:
    x1 present  {printf(" Interrogative Simple Future Tense");}
    ;
s:
    SUBJECT     {printf("Subject");}
    ;
p:
    VERB2       {printf("Verb2");}
    ;
x1:
    AUX1        {printf("will");}
    ;
x2:
    AUX2        {printf("did");}
    ;
v:
    VERB1       {printf("Verb");}
    ;
neg:
    NOT         {printf("Negative");}
    ;

%%
void yyerror(char *msg){
    fprintf(stderr, "%s\n", msg);
    exit(1);
}

int main()
{
    yyparse();
    return 0;
}

每当我尝试运行过去和futint时，似乎都会出现语法错误。现在也是一个错误，因为在受试者后立即遵循动词（v）。我期望如果我输入“他会吃吗？”或“你跑了吗？”输出将是“接受的辅助主题动词Verb1简单的过去/将来时态句子接受”。但是我目前得到的输出是“辅助主题语法错误”。谁能帮我解决这个问题？