partLen = c.Rand.Intn(63) + 1 // len is [1, 63]
	}

	runes := make([]rune, partLen)
	if partLen == 0 {
		return string(runes)
	}

	runes[0] = validStartEnd[c.Rand.Intn(len(validStartEnd))].choose(c.Rand)
	for i := range runes[1:] {
		runes[i+1] = validMiddle[c.Rand.Intn(len(validMiddle))].choose(c.Rand)
	}
	runes[len(runes)-1] = validStartEnd[c.Rand.Intn(len(validStartEnd))].choose(c.Rand)

	}
	// The open bracket must be preceeded by a link-adjacent rune (or by nothing).
	if t := plainText(i - 1); t != "" {
		r, _ := utf8.DecodeLastRuneInString(t)
		if !isLinkAdjacentRune(r) {
			return ""
		}
	}
	// The element after the next must be a ']'.
	if plainText(i+2) != "]" {
		return ""
	}
	// The ']' must be followed by a link-adjacent rune (or by nothing).
	if t := plainText(i + 3); t != "" {

			t.Errorf("%s(%q) = %q; want %q", funcName, tc.in, actual, tc.out)
		}
	}
}

func tenRunes(r rune) string {
	runes := make([]rune, 10)
	for i := range runes {
		runes[i] = r
	}
	return string(runes)
}

// User-defined self-inverse mapping function
func rot13(r rune) rune {
	const step = 13
	if r >= 'a' && r <= 'z' {
		return ((r - 'a' + step) % 26) + 'a'
	}

	if isComplex(Vu) && isComplex(Tu) {
		return true
	}

	// "V is an integer or a slice of bytes or runes and T is a string type"
	if (isInteger(Vu) || isBytesOrRunes(Vu)) && isString(Tu) {
		return true
	}

	// "V is a string and T is a slice of bytes or runes"
	if isString(Vu) && isBytesOrRunes(Tu) {
		return true
	}

	// package unsafe:

type Reader struct {
	// Comma is the field delimiter.
	// It is set to comma (',') by NewReader.
	// Comma must be a valid rune and must not be \r, \n,
	// or the Unicode replacement character (0xFFFD).
	Comma rune

	// Comment, if not 0, is the comment character. Lines beginning with the
	// Comment character without preceding whitespace are ignored.

	if isComplex(Vu) && isComplex(Tu) {
		return true
	}

	// "V is an integer or a slice of bytes or runes and T is a string type"
	if (isInteger(Vu) || isBytesOrRunes(Vu)) && isString(Tu) {
		return true
	}

	// "V is a string and T is a slice of bytes or runes"
	if isString(Vu) && isBytesOrRunes(Tu) {
		return true
	}

	// package unsafe:

	{"x \xc0\xc0 ", "x \xc0\xc0"},
	{"x ☺\xc0\xc0 ", "x ☺\xc0\xc0"},
	{"x ☺ ", "x ☺"},
}

func tenRunes(ch rune) string {
	r := make([]rune, 10)
	for i := range r {
		r[i] = ch
	}
	return string(r)
}

// User-defined self-inverse mapping function
func rot13(r rune) rune {
	step := rune(13)
	if r >= 'a' && r <= 'z' {
		return ((r - 'a' + step) % 26) + 'a'
	}
	if r >= 'A' && r <= 'Z' {

	// the closure once per rune.
	prev := ' '
	return Map(
		func(r rune) rune {
			if isSeparator(prev) {
				prev = r
				return unicode.ToTitle(r)
			}
			prev = r
			return r
		},
		s)
}

// TrimLeftFunc returns a slice of the string s with all leading
// Unicode code points c satisfying f(c) removed.
func TrimLeftFunc(s string, f func(rune) bool) string {
	i := indexFunc(s, f, false)

		}
		in.readRune()
	}
	in.endToken(_IDENT)
}

// isIdent reports whether c is an identifier rune.
// We treat most printable runes as identifier runes, except for a handful of
// ASCII punctuation characters.
func isIdent(c int) bool {
	switch r := rune(c); r {
	case ' ', '(', ')', '[', ']', '{', '}', ',':
		return false
	default:
		return !unicode.IsSpace(r) && unicode.IsPrint(r)
	}

The [RuneLen] function returns the number of 16-bit words in
the UTF-16 encoding of the rune. It returns -1 if the rune