%{
#include <stdio.h>
#include <stdlib.h>
extern int yylex();
extern int yylval;
extern int yyparse();
%}
 
%token NUMBER
 
%%
 
expr:
    expr '+' expr { $$ = $1 + $3; }
  | expr '-' expr { $$ = $1 - $3; }
  | '+' expr      { $$ = $2; }  // Unary plus does nothing, just returns the number
  | '-' expr      { $$ = -$2; } // Unary minus negates the number
  | '*' expr      { $$ = -$2; } // Treat * as unary minus
  | '/' expr      { $$ = -$2; } // Treat / as unary minus
  | NUMBER        { $$ = $1; }
  ;
 
%%
 
int main() {
    printf("Enter an expression: ");
    yyparse();
    return 0;
}
 
int yyerror(const char *s) {
    fprintf(stderr, "%s\n", s);
    return 0;
}
 

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

MjktMTIgPSAxNwo1MCsxNiA9IDY2

29-12 = 17
50+16 = 66