(p)
for_or_if :  for_loop expression %prec THEN
                |   IF "(" expression ")" expression opt_else
for_or_if :  for_loop expression %prec THEN
                |   IF "(" expression ")" expression opt_else
for_or_if : for_loop expression %prec THEN | IF ( expression ) expression opt_else
def p_for_or_if(p):
    '''for_or_if :  for_loop expression %prec THEN
                |   IF "(" expression ")" expression opt_else
       '''
def p_for_or_if ( p ) :