// is odd so we take the low bit from _case.
				return rune(cr.Lo) + ((r-rune(cr.Lo))&^1 | rune(_case&1)), true
			}
			return r + delta, true
		}
		if r < rune(cr.Lo) {
			hi = m
		} else {
			lo = m + 1
		}
	}
	return r, false
}

// To maps the rune to the specified case: [UpperCase], [LowerCase], or [TitleCase].
func To(_case int, r rune) rune {
	r, _ = to(_case, r, CaseRanges)
	return r
}

	bn := rb.rune[pos].pos
	sz := utf8.EncodeRune(rb.byte[bn:], rune(r))
	rb.rune[pos] = Properties{pos: bn, size: uint8(sz)}
}

// runeAt returns the rune at position n. It is used for Hangul and recomposition.
func (rb *reorderBuffer) runeAt(n int) rune {
	inf := rb.rune[n]
	r, _ := utf8.DecodeRune(rb.byte[inf.pos : inf.pos+inf.size])
	return r
}

		return rune(p0&mask2)<<6 | rune(b1&maskx), 2
	}
	b2 := p[2]
	if b2 < locb || hicb < b2 {
		return RuneError, 1
	}
	if sz <= 3 {
		return rune(p0&mask3)<<12 | rune(b1&maskx)<<6 | rune(b2&maskx), 3
	}
	b3 := p[3]
	if b3 < locb || hicb < b3 {
		return RuneError, 1
	}
	return rune(p0&mask4)<<18 | rune(b1&maskx)<<12 | rune(b2&maskx)<<6 | rune(b3&maskx), 4
}

			if len(inst.Next) > 0 {
				break
			}
			instQueue.insert(inst.Out)
			if len(inst.Rune) == 0 {
				onePassRunes[pc] = []rune{}
				inst.Next = []uint32{inst.Out}
				break
			}
			runes := make([]rune, 0)
			if len(inst.Rune) == 1 && syntax.Flags(inst.Arg)&syntax.FoldCase != 0 {
				r0 := inst.Rune[0]
				runes = append(runes, r0, r0)

}

func appendQuotedRuneWith(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
	buf = append(buf, quote)
	if !utf8.ValidRune(r) {
		r = utf8.RuneError
	}
	buf = appendEscapedRune(buf, r, quote, ASCIIonly, graphicOnly)
	buf = append(buf, quote)
	return buf
}

func appendEscapedRune(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
	if r == rune(quote) || r == '\\' { // always backslashed

	bn := rb.rune[pos].pos
	sz := utf8.EncodeRune(rb.byte[bn:], rune(r))
	rb.rune[pos] = Properties{pos: bn, size: uint8(sz)}
}

// runeAt returns the rune at position n. It is used for Hangul and recomposition.
func (rb *reorderBuffer) runeAt(n int) rune {
	inf := rb.rune[n]
	r, _ := utf8.DecodeRune(rb.byte[inf.pos : inf.pos+inf.size])
	return r
}

	case OpLiteral:
		for _, r := range re.Rune {
			escape(b, r, false)
		}
	case OpCharClass:
		if len(re.Rune)%2 != 0 {
			b.WriteString(`[invalid char class]`)
			break
		}
		b.WriteRune('[')
		if len(re.Rune) == 0 {
			b.WriteString(`^\x00-\x{10FFFF}`)
		} else if re.Rune[0] == 0 && re.Rune[len(re.Rune)-1] == unicode.MaxRune && len(re.Rune) > 2 {
			// Contains 0 and MaxRune. Probably a negated class.

		}
	}
	return
}

func (s *Scanner) scanNumber(ch rune, seenDot bool) (rune, rune) {
	base := 10         // number base
	prefix := rune(0)  // one of 0 (decimal), '0' (0-octal), 'x', 'o', or 'b'
	digsep := 0        // bit 0: digit present, bit 1: '_' present
	invalid := rune(0) // invalid digit in literal, or 0

	// integer part
	var tok rune
	var ds int
	if !seenDot {
		tok = Int
		if ch == '0' {

// Scanners may do rune-at-a-time scanning or ask the ScanState
// to discover the next space-delimited token.
type ScanState interface {
	// ReadRune reads the next rune (Unicode code point) from the input.
	// If invoked during Scanln, Fscanln, or Sscanln, ReadRune() will
	// return EOF after returning the first '\n' or when reading beyond
	// the specified width.
	ReadRune() (r rune, size int, err error)

		sep := ""
		for i := 0; i < len(re.Rune); i += 2 {
			b.WriteString(sep)
			sep = " "
			lo, hi := re.Rune[i], re.Rune[i+1]
			if lo == hi {
				fmt.Fprintf(b, "%#x", lo)
			} else {
				fmt.Fprintf(b, "%#x-%#x", lo, hi)
			}
		}
	}
	b.WriteByte('}')
}

func mkCharClass(f func(rune) bool) string {
	re := &Regexp{Op: OpCharClass}
	lo := rune(-1)
	for i := rune(0); i <= unicode.MaxRune; i++ {