}

var errUnreadByte = errors.New("bytes.Buffer: UnreadByte: previous operation was not a successful read")

// UnreadByte unreads the last byte returned by the most recent successful
// read operation that read at least one byte. If a write has happened since
// the last read, if the last read returned an error, or if the read read zero
// bytes, UnreadByte returns an error.
func (b *Buffer) UnreadByte() error {

		q[j-1] = 1 // difference is only found on the last byte
		for i := range b {
			idx := Index(b[i:], q[:j])
			if idx != -1 {
				t.Fatalf("Index(b[%d:], q[:%d])=%d, want -1\n", i, j, idx)
			}
		}
		q[j-1] = 0
	}

	// Test differing alignments and sizes of q which always end on a page boundary.
	q[len(q)-1] = 1 // difference is only found on the last byte
	for j := 0; j < len(q); j++ {
		for i := range b {

	b := make([]byte, 0, len(s))
	for _, c := range s {
		if c < 0x80 && c != 0x00 {
			b = append(b, byte(c))
		}
	}
	return string(b)
}

type parser struct {
	err error // Last error seen
}

type formatter struct {
	err error // Last error seen
}

// parseString parses bytes as a NUL-terminated C-style string.
// If a NUL byte is not found then the whole slice is returned as a string.

//
// Scanning stops unrecoverably at EOF, the first I/O error, or a token too
// large to fit in the [Scanner.Buffer]. When a scan stops, the reader may have
// advanced arbitrarily far past the last token. Programs that need more
// control over error handling or large tokens, or must run sequential scans
// on a reader, should use [bufio.Reader] instead.
type Scanner struct {

		{"VADDPD.Z.A X0, X1, X2", `Z suffix should be the last; unknown suffix "A"`},
		{"VADDPD.Z.Z X0, X1, X2", `Z suffix should be the last; duplicate suffix "Z"`},
		{"VADDPD.SAE.BCST X0, X1, X2", `can't combine rounding/SAE and broadcast`},
		{"VADDPD.BCST.SAE X0, X1, X2", `can't combine rounding/SAE and broadcast`},
		{"VADDPD.BCST.Z.SAE X0, X1, X2", `Z suffix should be the last; can't combine rounding/SAE and broadcast`},

	// Invalid input: strconv.ParseInt: parsing "1234567901234567890": value out of range
}

// Use a Scanner with a custom split function to parse a comma-separated
// list with an empty final value.
func ExampleScanner_emptyFinalToken() {
	// Comma-separated list; last entry is empty.
	const input = "1,2,3,4,"
	scanner := bufio.NewScanner(strings.NewReader(input))
	// Define a split function that separates on commas.

[56789a].out
*~
*.orig
*.rej
*.exe
.*.swp
core
*.cgo*.go
*.cgo*.c
_cgo_*
_obj
_test
_testmain.go

/VERSION.cache
/bin/
/build.out
/doc/articles/wiki/*.bin
/goinstall.log
/last-change
/misc/cgo/life/run.out
/misc/cgo/stdio/run.out
/misc/cgo/testso/main
/pkg/
/src/*.*/
/src/cmd/cgo/zdefaultcc.go
/src/cmd/dist/dist
/src/cmd/go/internal/cfg/zdefaultcc.go

	return bytealg.IndexByte(b, c)
}

func indexBytePortable(s []byte, c byte) int {
	for i, b := range s {
		if b == c {
			return i
		}
	}
	return -1
}

// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
func LastIndex(s, sep []byte) int {
	n := len(sep)
	switch {
	case n == 0:
		return len(s)
	case n == 1:
		return bytealg.LastIndexByte(s, sep[0])

		if first != tc.first {
			t.Errorf("IndexFunc(%q, %s) = %d; want %d", tc.in, tc.f.name, first, tc.first)
		}
		last := LastIndexFunc([]byte(tc.in), tc.f.f)
		if last != tc.last {
			t.Errorf("LastIndexFunc(%q, %s) = %d; want %d", tc.in, tc.f.name, last, tc.last)
		}
	}
}

type ReplaceTest struct {
	in       string
	old, new string
	n        int
	out      string
}

</pre>

<p>
Within a parenthesized <code>const</code> declaration list the
expression list may be omitted from any but the first ConstSpec.
Such an empty list is equivalent to the textual substitution of the
first preceding non-empty expression list and its type if any.
Omitting the list of expressions is therefore equivalent to
repeating the previous list.  The number of identifiers must be equal