%{
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include "lex.yy.c"
extern int yylval;
 int symcount=0;
 int stk[1000];
 int sptr=1;
 int temp;
typedef int YYSTYPE;
 %}
%token IF
%token ELSE
%token ENDIF
%token ID
%token ASSIGN
%token NUM
%token PRINT
%left '<' '>' GE LE EQ NE
%left '+' '-'
%left '*' '/'
%left UMINUS
%token THEN


%start stmtlist

%%
stmtlist: stmtlist  stmt  
| stmt 
;
stmt: ID ASSIGN expr ';' { if (top() >=1) sym_tbl[$1].value=$3;}
| PRINT expr ';' { if (top() >=1 ) printf("%d\n", $2); }
| IF expr { if (top() >=1) push ($2 != 0); else push(0);}THEN stmtlist {pop();} ELSE {if (top() >=1) push ($2 ==0); else push(0);} stmtlist {pop();} ENDIF;
   ;
expr : expr '+' expr  { if (top() >= 1)$$=$1+$3;}
    | expr '-' expr { if (top() >= 1) $$ =$1-$3; }
     | expr '/' expr  { if (top() >=1 )$$ = $1/$3;}
| expr '*' expr { if (top() >=1) $$ = $1*$3; }
| expr '>' expr { if (top()>=1) {if ($1 > $3) $$=1; else $$=0;}}
| expr '<' expr { if (top() >=1 ){if ($1 < $3) $$=1; else $$=0;}}
| expr GE expr  { if (top() >=1 ) {if ($1 >= $3) $$=1; else $$=0;}}
| expr LE expr { if (top() >=1 ) { if ($1 <= $3) $$=1; else $$=0;}}
 | expr EQ expr { if (top() >=1 ) {if ($1 == $3) $$=1; else $$=0;}}
 | expr NE expr { if (top() >=1) { if($1 != $3) $$=1; else $$=0;}}
| '(' expr ')' { $$ =  $2;}
       | ID { $$=sym_tbl[$1].value;}
       | NUM {$$ = sym_tbl[$1].value;}
       ;

%%

void main()
{
  do 
    {
      stk[0]=1;
      sptr=1;
      yyparse();
    }
  while(!feof(stdin));
}

void yyerror(char *msg)
{
 printf("%s\n",msg);
}

void push(int x)
{
  stk[sptr++]=x;
}
void pop(void)
{
  sptr--;
  
}

int top(void)
{ return stk[sptr-1];}