// processing. A [Reader] that does not implement  ByteReader
// can be wrapped using bufio.NewReader to add this method.
type ByteReader interface {
	ReadByte() (byte, error)
}

// ByteScanner is the interface that adds the UnreadByte method to the
// basic ReadByte method.
//
// UnreadByte causes the next call to ReadByte to return the last byte read.

//	sign     = "+" | "-" .
//	digits   = digit { [ '_' ] digit } .
//	digit    = "0" ... "9" .
//
// A base 2 exponent is only permitted if base2ok is set.
func scanExponent(r io.ByteScanner, base2ok, sepOk bool) (exp int64, base int, err error) {
	// one char look-ahead
	ch, err := r.ReadByte()
	if err != nil {
		if err == io.EOF {
			err = nil
		}
		return 0, 10, err
	}

// is set, only), and -count is the number of fractional digits found.
// In this case, the actual value of the scanned number is res * b**count.
func (z nat) scan(r io.ByteScanner, base int, fracOk bool) (res nat, b, count int, err error) {
	// reject invalid bases
	baseOk := base == 0 ||
		!fracOk && 2 <= base && base <= MaxBase ||
		fracOk && (base == 2 || base == 8 || base == 10 || base == 16)

func (z *Int) SetString(s string, base int) (*Int, bool) {
	return z.setFromScanner(strings.NewReader(s), base)
}

// setFromScanner implements SetString given an io.ByteScanner.
// For documentation see comments of SetString.
func (z *Int) setFromScanner(r io.ByteScanner, base int) (*Int, bool) {
	if _, _, err := z.scan(r, base); err != nil {
		return nil, false
	}
	// entire content must have been consumed