%{
int names[26];
%}

%token NUMBER NAME PLUS MINUS STAR DIV LPAR RPAR EQUALS


%%

stmt_lst: stmt '\n'
	| stmt_lst stmt '\n'
	;

stmt	: NAME EQUALS expr	{ $$ = $3; printf("=> %d\n", $3); names[$1]=$3; }
	| expr			{ $$ = $1; printf("=> %d\n", $1); }
	;

expr	: expr PLUS term	{ $$ = $1 + $3; }
	| expr MINUS term	{ $$ = $1 - $3; }
	| term			{ $$ = $1; }
	;

term	: term STAR prim	{ $$ = $1 * $3; }
	| term DIV prim		{
				if ($3 == 0) { yyerror("divide by zero"); exit(1); }
				else         $$ = $1 / $3;
				}
	| prim			{ $$ = $1; }
	;

prim	: LPAR expr RPAR	{ $$ = $2; }
	| MINUS prim		{ $$ = - $2; }
	| NUMBER		{ $$ = $1; }
	| NAME			{ $$ = names[yylval]; }
	;

%%