case scanner.Int:
		return p.atoi(tok.String())
	case scanner.Char:
		str, err := strconv.Unquote(tok.String())
		if err != nil {
			p.errorf("%s", err)
		}
		r, w := utf8.DecodeRuneInString(str)
		if w == 1 && r == utf8.RuneError {
			p.errorf("illegal UTF-8 encoding for character constant")
		}
		return uint64(r)
	case '+':
		return +p.factor()
	case '-':
		return -p.factor()