func (x *Lexer) accept(valid string) bool {
	if strings.IndexRune(valid, x.peek()) >= 0 {
		x.next()
		return true
	}
	return false
}
// accept consumes the next rune if it's from the given set of valid runes.
accept consumes the next rune if it's from the given set of valid runes.
// accept consumes the next rune if it ' s from the given set of valid runes .
func (x *Lexer) accept(valid string) bool {
	if strings.IndexRune(valid, x.peek()) >= 0 {
		x.next()
		return true
	}
	return false
}
func ( x * Lexer ) accept ( valid string ) bool { if strings . IndexRune ( valid , x . peek ( ) ) >= 0 { x . next ( ) return true } return false }
accept consumes the next rune if it's from the given set of valid runes.
accept consumes the next rune if it ' s from the given set of valid runes .