(t)
expression : MINUS expression %prec UMINUS
expression : MINUS expression %prec UMINUS
expression : MINUS expression %prec UMINUS
def p_expression_uminus(t):
    'expression : MINUS expression %prec UMINUS'
    t[0] = -t[2]
def p_expression_uminus ( t ) : t [ 0 ] = - t [ 2 ]