// returning nil instead of empty slice if all spaces.
		return nil
	}
	return s[start:stop]
}

// Runes interprets s as a sequence of UTF-8-encoded code points.
// It returns a slice of runes (Unicode code points) equivalent to s.
func Runes(s []byte) []rune {
	t := make([]rune, utf8.RuneCount(s))
	i := 0
	for len(s) > 0 {
		r, l := utf8.DecodeRune(s)
		t[i] = r
		i++

	// TODO(quasilyte): improve error message (#21860).
	V4FMADDPS (AX), [Z0-Z4], K1, Z7  // ERROR "invalid instruction"
	V4FMADDPS (AX), [Z0-Z0], K1, Z7  // ERROR "invalid instruction"
	// Invalid ranges in REG_LIST (low > high).
	// TODO(quasilyte): improve error message (#21860).
	V4FMADDPS (AX), [Z4-Z0], K1, Z7  // ERROR "invalid instruction"
	V4FMADDPS (AX), [Z1-Z0], K1, Z7  // ERROR "invalid instruction"

		a.Reg = 0
		a.Index = r1
		a.Scale = int16(scale)
	}
}

// registerList parses an ARM or ARM64 register list expression, a list of
// registers in []. There may be comma-separated ranges or individual
// registers, as in [R1,R3-R5] or [V1.S4, V2.S4, V3.S4, V4.S4].
// For ARM, only R0 through R15 may appear.
// For ARM64, V0 through V31 with arrangement may appear.
//

</li>

<li>
Converting a slice of runes to a string type yields
a string that is the concatenation of the individual rune values
converted to strings.

<pre>
string([]rune{0x767d, 0x9d6c, 0x7fd4})   // "\u767d\u9d6c\u7fd4" == "白鵬翔"
string([]rune{})                         // ""
string([]rune(nil))                      // ""

type runes []rune

pkg crypto/tls, type RenegotiationSupport int
pkg crypto/x509, func SystemCertPool() (*CertPool, error)
pkg crypto/x509, type SystemRootsError struct, Err error
pkg debug/dwarf, method (*Data) Ranges(*Entry) ([][2]uint64, error)
pkg debug/dwarf, method (*Reader) SeekPC(uint64) (*Entry, error)
pkg debug/elf, const R_390_12 = 2
pkg debug/elf, const R_390_12 R_390
pkg debug/elf, const R_390_16 = 3

// UTF-8-encoded rune as a token. The sequence of runes returned is
// equivalent to that from a range loop over the input as a string, which
// means that erroneous UTF-8 encodings translate to U+FFFD = "\xef\xbf\xbd".
// Because of the Scan interface, this makes it impossible for the client to
// distinguish correctly encoded replacement runes from encoding errors.

		}
		if !Equal(actual, tc.out) {
			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' {

}

func ExampleReplaceAll() {
	fmt.Printf("%s\n", bytes.ReplaceAll([]byte("oink oink oink"), []byte("oink"), []byte("moo")))
	// Output:
	// moo moo moo
}

func ExampleRunes() {
	rs := bytes.Runes([]byte("go gopher"))
	for _, r := range rs {
		fmt.Printf("%#U\n", r)
	}
	// Output:
	// U+0067 'g'
	// U+006F 'o'
	// U+0020 ' '
	// U+0067 'g'
	// U+006F 'o'
	// U+0070 'p'
	// U+0068 'h'

	switch {
	case !utf8Valid1 || !utf8Valid2:
		// Name and Comment definitely not UTF-8.
		f.NonUTF8 = true
	case !utf8Require1 && !utf8Require2:
		// Name and Comment use only single-byte runes that overlap with UTF-8.
		f.NonUTF8 = false
	default:
		// Might be UTF-8, might be some other encoding; preserve existing flag.
		// Some ZIP writers use UTF-8 encoding without setting the UTF-8 flag.

			t.Errorf("#%d: got error %v; want EOF", rno, err)
		}
	}
}

// Test that UnreadRune fails if the preceding operation was not a ReadRune.
func TestUnreadRuneError(t *testing.T) {
	buf := make([]byte, 3) // All runes in this test are 3 bytes long
	r := NewReader(&StringReader{data: []string{"日本語日本語日本語"}})
	if r.UnreadRune() == nil {
		t.Error("expected error on UnreadRune from fresh buffer")
	}
	_, _, err := r.ReadRune()