%{
#include <stdio.h>
%}

%token NAME NUMBER
%left '-' '+'
%left '*' '/'
%nonassoc UMINUS

%%
statement:	NAME '=' expression		{ printf("pretending to assign %s the value %d\n", $1, $3); }
	;
	|	expression			{ printf("= %d\n", $1); }
	;
expression:	expression '+' expression	{ $$ = $1 + $3;
						printf ("Recognized '+' expression.\n");
						}
	|	expression '-' expression	{ $$ = $1 - $3; 
						printf ("Recognized '-' expression.\n");
						}
	|	expression '*' expression	{ $$ = $1 * $3; 
						printf ("Recognized '*' expression.\n");
						}
	|	expression '/' expression	{ if ($3 == 0)
							yyerror ("divide by zero");
						else
							$$ = $1 / $3; 
						printf ("Recognized '/' expression.\n");
						}
	|	'-' expression %prec UMINUS	{ $$ = - $2; 
						printf ("Recognized negation.\n");
						}
	|	'(' expression ')'		{ $$ = $2;
						printf ("Recognized parenthesized expression.\n");
						}
	|	NUMBER				{ $$ = $1; 
						printf ("Recognized a number.\n");
						}
	;
%%
int main (void) {
	return yyparse();
	}

/* Added because panther doesn't have liby.a installed. */
int yyerror (char *msg) {
	return fprintf (stderr, "YACC: %s\n", msg);
	}