in.Error("mod files must use // comments (not /* */ comments)")
		}
		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:

	if c.errStart > 0 {
		for i := 1; i < c.errStart; i++ {
			c.link[i].p, c.link[i].n = 0, 0
		}
		err, c.errStart, c.err = c.err, 0, nil
	}
	return dstL.n, srcL.p, err
}

// Deprecated: Use runes.Remove instead.
func RemoveFunc(f func(r rune) bool) Transformer {
	return removeF(f)
}

type removeF func(r rune) bool

func (removeF) Reset() {}

// Transform implements the Transformer interface.

	s := strconv.Quote(x.string())
	if utf8.RuneCountInString(s) > maxLen {
		// The string without the enclosing quotes is greater than maxLen-2 runes
		// long. Remove the last 3 runes (including the closing '"') by keeping
		// only the first maxLen-3 runes; then add "...".
		i := 0
		for n := 0; n < maxLen-3; n++ {
			_, size := utf8.DecodeRuneInString(s[i:])
			i += size
		}
		s = s[:i] + "..."
	}

// But there are at least two subtle considerations.
//
// First, note that not all case-fold equivalent distinct runes
// form an upper/lower pair.
// For example, U+004B ('K'), U+006B ('k'), and U+212A ('K' for Kelvin)
// are three distinct runes that case-fold to each other.
// When we do add Unicode letters, we must not assume that upper/lower
// are the only case-equivalent pairs.

		Data:  Data{off + entryLen, size},
	})
}

// exactly16Bytes truncates the string if necessary so it is at most 16 bytes long,
// then pads the result with spaces to be exactly 16 bytes.
// Fmt uses runes for its width calculation, but we need bytes in the entry header.
func exactly16Bytes(s string) string {
	for len(s) > 16 {
		_, wid := utf8.DecodeLastRuneInString(s)
		s = s[:len(s)-wid]
	}

	return s
}

// replace replaces each rune r of s with replacementTable[r], provided that
// r < len(replacementTable). If replacementTable[r] is the empty string then
// no replacement is made.
// It also replaces runes U+2028 and U+2029 with the raw strings `\u2028` and
// `\u2029`.
func replace(s string, replacementTable []string) string {
	var b strings.Builder
	r, w, written := rune(0), 0, 0
	for i := 0; i < len(s); i += w {

<li>
Converting a value of a string type to a slice of runes type
yields a slice containing the individual Unicode code points of the string.

<pre>
[]rune(myString("白鵬翔"))   // []rune{0x767d, 0x9d6c, 0x7fd4}
[]rune("")                  // []rune{}

runes("白鵬翔")              // []rune{0x767d, 0x9d6c, 0x7fd4}

[]myRune("♫♬")              // []myRune{0x266b, 0x266c}
[]myRune(myString("🌐"))    // []myRune{0x1f310}
</pre>

// the start of the field with the given index in the slice most recently
// returned by [Reader.Read]. Numbering of lines and columns starts at 1;
// columns are counted in bytes, not runes.
//
// If this is called with an out-of-bounds index, it panics.
func (r *Reader) FieldPos(field int) (line, column int) {
	if field < 0 || field >= len(r.fieldPositions) {
		panic("out of range index passed to FieldPos")

	"(" + strings.Repeat("(xx?)", 1000) + "){1000}",          // too long
	strings.Repeat("(xx?){1000}", 1000),                      // too long
	strings.Repeat(`\pL`, 27000),                             // too many runes
}

var onlyPerl = []string{
	`[a-b-c]`,
	`\Qabc\E`,
	`\Q*+?{[\E`,
	`\Q\\E`,
	`\Q\\\E`,
	`\Q\\\\E`,
	`\Q\\\\\E`,
	`(?:a)`,
	`(?P<name>a)`,
}

var onlyPOSIX = []string{

		r, wid := utf8.DecodeRuneInString(s)
		s = s[wid:]
		if wid > 1 {
			if r == '\ufeff' {
				return false // BOMs are invisible and should not be quoted.
			}
			continue // All other multibyte runes are correctly encoded and assumed printable.
		}
		if r == utf8.RuneError {
			return false
		}
		if (r < ' ' && r != '\t') || r == '`' || r == '\u007F' {
			return false
		}
	}
	return true
}