yacc and lex code for three address code statements

here is my lex code: three.l

%{
#include "y.tab.h"
#include "string.h"
%}
%%
[a-zA-Z]+ { yylval.a_var=(char *)malloc(sizeof(char *));
         strcpy(yylval.a_var,yytext);
         return var;}
[-+/*,]   {return yytext[0];}

[\t\n] return开发者_如何学编程 0;

%%

my yacc is

three.y

%{

#include "stdio.h"

#include "string.h"

int yywrap()

{


return 1;
}

static int i;


int d;

char temp();

%}

%left '+' '-'

%left '*' '/'

%union{char *a_var;}

%token id

%token <a_var>var

%start line


%%
line:var '=' exp {printf("%c=t%c\n",$1,$3);}

;
exp:exp '+' exp   {$$=temp();if(i<=1){printf("t%c=%c+%c\n",$$,$1,$3);}  else{printf("t%c=t%c+%c\n",$$,$1,$3);} }

|exp '-' exp       {$$=temp();if(i<=1){printf("t%c=%c-%c\n",$$,$1,$3); } else{printf("t%c=t%c-%c\n",$$,$1,$3);} }

|exp '*' exp        {$$=temp();if(i<=1){printf("t%c=%c*%c\n",$$,$1,$3); } else{printf("t%c=t%c*%c\n",$$,$1,$3);} }

|exp '/' exp       {$$=temp();if(i<=1){printf("t%c=%c/%c\n",$$,$1,$3); } else {printf("t%c=t%c/%c\n",$$,$1,$3);} }

|var    {$$=$1;}

;

%%

main()

{

yyparse();

return 0;

}

int yyerror(char *s)

{



fprintf(stderr,"%s\n",s);

}

char temp()

{

return('1'+ i++);

}

but when i compile this

three.y:19.40-41: $3 of `line' has no declared type

three.y:21.20-21: $$ of `exp' has no declared type

three.y:21.60-61: $$ of `exp' has no declared type

three.y:21.63-64: $1 of `exp' has no declared type

three.y:21.66-67: $3 of `exp' has no declared type

three.y:21.100-101: $$ of `exp' has no declared type

three.y:21.103-104: $1 of `exp' has no declared type

three.y:21.106-107: $3 of `exp' has no declared type

three.y:22.21-22: $$ of `exp' has no declared type

three.y:22.61-62: $$ of `exp' has no declared type

three.y:22.64-65: $1 of `exp' has no declared type

three.y:22.67-68: $3 of `exp' has no declared type

three.y:22.104-105: $1 of `exp' has no declared type

three.y:22.107-108: $3 of `exp' has no declared type

three.y:23.22-23: $$ of `exp' has no declared type

three.y:23.62-63: $$ of `exp' has no declared type

three.y:23.65-66: $1 of `exp' has no declared type

three.y:23.68-69: $3 of `exp' has no declared type

three.y:23.102-103: $$ of `exp' has no declared type

three.y:23.105-106: $1 of `exp' has no declared type

three.y:23.108-109: $3 of `exp' has no declared type

three.y:24.21-22: $$ of `exp' has no declared type

three.y:24.61-62: $$ of `exp' has no declared type

three.y:24.64-65: $1 of `exp' has no declared type

three.y:24.67-68: $3 of `exp' has no declared type

three.y:24.102-103: $$ of `exp' has no declared type

three.y:24.105-106: $1 of `exp' has no declared type

three.y:24.108-109: $3 of `exp' has no declared type

three.y:25.10-11: $$ of `exp' has no declared type

pla help me to solve this..

add the line

%type <a_var> exp

to your code, you need to define the exp.

When you use a %union for your yystype, then when you refer to yylval you have to say which member of the union to use. So with your union

%union{char *a_var;}

when you say

line:var '=' exp {printf("%c=t%c\n",$1,$3);}

you should say instead something like $1.a_var:

line:var '=' exp {printf("%c=t%c\n",$1.a_var,$3.a_var);}

As far as I see, the types of the semantic values of line and exp seem not to be specified in your code.
So, I think specifying the types like %type <a_var> line exp will solve the error.
Hope this helps