fmt.Scan: field widths

Also fix an interface bug: white-space-delimited doesn't work well for cases like "%d, %d" on "23, 23")

R=rsc
CC=golang-dev
https://golang.org/cl/1502041

src/pkg/fmt/print.go

@@ -80,12 +80,11 @@
 	Scanning:
 
 	An analogous set of functions scans formatted text to yield
-	values.  Scan and Scanln read from os.Stdin; Fscan and Fscanln
-	read from a specified os.Reader; Sscan and Sscanln read from
-	an argument string.  By default, tokens are separated by
-	spaces.  Sscanln, Fscanln and Sscanln stop scanning at a
-	newline and require that the items be followed by one; the
-	other routines treat newlines as spaces.
+	values.  Scan and Scanln read from os.Stdin; Fscan and
+	Fscanln read from a specified os.Reader; Sscan and Sscanln
+	read from an argument string.  Sscanln, Fscanln and Sscanln
+	stop scanning at a newline and require that the items be
+	followed by one; the other routines treat newlines as spaces.
 
 	Scanf, Fscanf, and Sscanf parse the arguments according to a
 	format string, analogous to that of Printf.  For example, "%x"
@@ -99,6 +98,12 @@
 	%T is not implemented
 	%e %E %f %F %g %g are all equivalent and scan any floating
 		point or complex value
+	%s and %v on strings scan a space-delimited token
+
+	Width is interpreted in the input text (%5s means at most
+	five runes of input will be read to scan a string) but there
+	is no syntax for scanning with a precision (no %5.2f, just
+	%5f).
 
 	When scanning with a format, all non-empty runs of space
 	characters (including newline) are equivalent to a single
@@ -118,8 +123,6 @@
 */
 package fmt
 
-// BUG: format precision and flags are not yet implemented for scanning.
-
 import (
 	"bytes"
 	"io"

src/pkg/fmt/scan.go

@@ -30,7 +30,12 @@ type ScanState interface {
 	GetRune() (rune int, err os.Error)
 	// UngetRune causes the next call to GetRune to return the rune.
 	UngetRune(rune int)
-	// Token returns the next space-delimited token from the input.
+	// Width returns the value of the width option and whether it has been set.
+	// The unit is Unicode code points.
+	Width() (wid int, ok bool)
+	// Token returns the next space-delimited token from the input. If
+	// a width has been specified, the returned token will be no longer
+	// than the width.
 	Token() (token string, err os.Error)
 }
 
@@ -39,7 +44,7 @@ type ScanState interface {
 // receiver, which must be a pointer to be useful.  The Scan method is called
 // for any argument to Scan or Scanln that implements it.
 type Scanner interface {
-	Scan(ScanState) os.Error
+	Scan(state ScanState, verb int) os.Error
 }
 
 // Scan scans text read from standard input, storing successive
@@ -126,6 +131,9 @@ type ss struct {
 	buf        bytes.Buffer // token accumulator
 	nlIsSpace  bool         // whether newline counts as white space
 	peekRune   int          // one-rune lookahead
+	maxWid     int          // max width of field, in runes
+	widPresent bool         // width was specified
+	wid        int          // width consumed so far; used in accept()
 }
 
 func (s *ss) GetRune() (rune int, err os.Error) {
@@ -138,6 +146,10 @@ func (s *ss) GetRune() (rune int, err os.Error) {
 	return
 }
 
+func (s *ss) Width() (wid int, ok bool) {
+	return s.maxWid, s.widPresent
+}
+
 const EOF = -1
 
 // The public method returns an error; this private one panics.
@@ -257,6 +269,8 @@ func newScanState(r io.Reader, nlIsSpace bool) *ss {
 	}
 	s.nlIsSpace = nlIsSpace
 	s.peekRune = -1
+	s.maxWid = 0
+	s.widPresent = false
 	return s
 }
 
@@ -273,7 +287,6 @@ func (s *ss) free() {
 
 // skipSpace skips spaces and maybe newlines
 func (s *ss) skipSpace() {
-	s.buf.Reset()
 	for {
 		rune := s.getRune()
 		if rune == EOF {
@@ -293,13 +306,13 @@ func (s *ss) skipSpace() {
 	}
 }
 
-// token returns the next space-delimited string from the input.
-// For Scanln, it stops at newlines.  For Scan, newlines are treated as
-// spaces.
+// token returns the next space-delimited string from the input.  It
+// skips white space.  For Scanln, it stops at newlines.  For Scan,
+// newlines are treated as spaces.
 func (s *ss) token() string {
 	s.skipSpace()
 	// read until white space or newline
-	for {
+	for nrunes := 0; !s.widPresent || nrunes < s.maxWid; nrunes++ {
 		rune := s.getRune()
 		if rune == EOF {
 			break
@@ -321,6 +334,30 @@ func (s *ss) typeError(field interface{}, expected string) {
 var intBits = uint(reflect.Typeof(int(0)).Size() * 8)
 var uintptrBits = uint(reflect.Typeof(int(0)).Size() * 8)
 var complexError = os.ErrorString("syntax error scanning complex number")
+var boolError = os.ErrorString("syntax error scanning boolean")
+
+// accepts checks the next rune in the input.  If it's a byte (sic) in the string, it puts it in the
+// buffer and returns true. Otherwise it return false.
+func (s *ss) accept(ok string) bool {
+	if s.wid >= s.maxWid {
+		return false
+	}
+	rune := s.getRune()
+	if rune == EOF {
+		return false
+	}
+	for i := 0; i < len(ok); i++ {
+		if int(ok[i]) == rune {
+			s.buf.WriteRune(rune)
+			s.wid++
+			return true
+		}
+	}
+	if rune != EOF {
+		s.UngetRune(rune)
+	}
+	return false
+}
 
 // okVerb verifies that the verb is present in the list, setting s.err appropriately if not.
 func (s *ss) okVerb(verb int, okVerbs, typ string) bool {
@@ -338,34 +375,73 @@ func (s *ss) scanBool(verb int) bool {
 	if !s.okVerb(verb, "tv", "boolean") {
 		return false
 	}
-	tok := s.token()
-	b, err := strconv.Atob(tok)
-	if err != nil {
-		s.error(err)
+	// Syntax-checking a boolean is annoying.  We're not fastidious about case.
+	switch s.mustGetRune() {
+	case '0':
+		return false
+	case '1':
+		return true
+	case 't', 'T':
+		if s.accept("rR") && (!s.accept("uU") || !s.accept("eE")) {
+			s.error(boolError)
 		}
-	return b
+		return true
+	case 'f', 'F':
+		if s.accept("aL") && (!s.accept("lL") || !s.accept("sS") || !s.accept("eE")) {
+			s.error(boolError)
+		}
+		return false
+	}
+	return false
 }
 
-// getBase returns the numeric base represented by the verb.
-func (s *ss) getBase(verb int) int {
+// Numerical elements
+const (
+	binaryDigits      = "01"
+	octalDigits       = "01234567"
+	decimalDigits     = "0123456789"
+	hexadecimalDigits = "0123456789aAbBcCdDeEfF"
+	sign              = "+-"
+	period            = "."
+	exponent          = "eE"
+)
+
+// getBase returns the numeric base represented by the verb and its digit string.
+func (s *ss) getBase(verb int) (base int, digits string) {
 	s.okVerb(verb, "bdoxXv", "integer") // sets s.err
-	base := 10
+	base = 10
+	digits = decimalDigits
 	switch verb {
 	case 'b':
 		base = 2
+		digits = binaryDigits
 	case 'o':
 		base = 8
+		digits = octalDigits
 	case 'x', 'X':
 		base = 16
+		digits = hexadecimalDigits
 	}
-	return base
+	return
+}
+
+// scanNumber returns the numerical string with specified digits starting here.
+func (s *ss) scanNumber(digits string) string {
+	if !s.accept(digits) {
+		s.errorString("expected integer")
+	}
+	for s.accept(digits) {
+	}
+	return s.buf.String()
 }
 
 // scanInt returns the value of the integer represented by the next
 // token, checking for overflow.  Any error is stored in s.err.
 func (s *ss) scanInt(verb int, bitSize uint) int64 {
-	base := s.getBase(verb)
-	tok := s.token()
+	base, digits := s.getBase(verb)
+	s.skipSpace()
+	s.accept(sign) // If there's a sign, it will be left in the token buffer.
+	tok := s.scanNumber(digits)
 	i, err := strconv.Btoi64(tok, base)
 	if err != nil {
 		s.error(err)
@@ -380,8 +456,9 @@ func (s *ss) scanInt(verb int, bitSize uint) int64 {
 // scanUint returns the value of the unsigned integer represented
 // by the next token, checking for overflow.  Any error is stored in s.err.
 func (s *ss) scanUint(verb int, bitSize uint) uint64 {
-	base := s.getBase(verb)
-	tok := s.token()
+	base, digits := s.getBase(verb)
+	s.skipSpace()
+	tok := s.scanNumber(digits)
 	i, err := strconv.Btoui64(tok, base)
 	if err != nil {
 		s.error(err)
@@ -393,56 +470,55 @@ func (s *ss) scanUint(verb int, bitSize uint) uint64 {
 	return i
 }
 
-// complexParts returns the strings representing the real and imaginary parts of the string.
-func (s *ss) complexParts(str string) (real, imag string) {
-	if len(str) > 2 && str[0] == '(' && str[len(str)-1] == ')' {
-		str = str[1 : len(str)-1]
-	}
-	real, str = floatPart(str)
-	// Must now have a sign.
-	if len(str) == 0 || (str[0] != '+' && str[0] != '-') {
-		s.error(complexError)
-	}
-	imag, str = floatPart(str)
-	if str != "i" {
-		s.error(complexError)
-	}
-	return real, imag
-}
-
-// floatPart returns strings holding the floating point value in the string, followed
-// by the remainder of the string.  That is, it splits str into (number,rest-of-string).
-func floatPart(str string) (first, last string) {
-	i := 0
+// floatToken returns the floating-point number starting here, no longer than swid
+// if the width is specified. It's not rigorous about syntax because it doesn't check that
+// we have at least some digits, but Atof will do that.
+func (s *ss) floatToken() string {
+	s.buf.Reset()
 	// leading sign?
-	if len(str) > i && (str[0] == '+' || str[0] == '-') {
-		i++
-	}
+	s.accept(sign)
 	// digits?
-	for len(str) > i && '0' <= str[i] && str[i] <= '9' {
-		i++
-	}
-	// period?
-	if str[i] == '.' {
-		i++
+	for s.accept(decimalDigits) {
 	}
+	// decimal point?
+	if s.accept(period) {
 		// fraction?
-	for len(str) > i && '0' <= str[i] && str[i] <= '9' {
-		i++
+		for s.accept(decimalDigits) {
+		}
 	}
 	// exponent?
-	if len(str) > i && (str[i] == 'e' || str[i] == 'E') {
-		i++
+	if s.accept(exponent) {
 		// leading sign?
-		if str[i] == '+' || str[i] == '-' {
-			i++
-		}
+		s.accept(sign)
 		// digits?
-		for len(str) > i && '0' <= str[i] && str[i] <= '9' {
-			i++
+		for s.accept(decimalDigits) {
+		}
+	}
+	return s.buf.String()
+}
+
+// complexTokens returns the real and imaginary parts of the complex number starting here.
+// The number might be parenthesized and has the format (N+Ni) where N is a floating-point
+// number and there are no spaces within.
+func (s *ss) complexTokens() (real, imag string) {
+	// TODO: accept N and Ni independently?
+	parens := s.accept("(")
+	real = s.floatToken()
+	s.buf.Reset()
+	// Must now have a sign.
+	if !s.accept("+-") {
+		s.error(complexError)
 	}
+	// Sign is now in buffer
+	imagSign := s.buf.String()
+	imag = s.floatToken()
+	if !s.accept("i") {
+		s.error(complexError)
 	}
-	return str[0:i], str[i:]
+	if parens && !s.accept(")") {
+		s.error(complexError)
+	}
+	return real, imagSign + imag
 }
 
 // convertFloat converts the string to a float value.
@@ -480,8 +556,8 @@ func (s *ss) scanComplex(verb int, atof func(*ss, string) float64) complex128 {
 	if !s.okVerb(verb, floatVerbs, "complex") {
 		return 0
 	}
-	tok := s.token()
-	sreal, simag := s.complexParts(tok)
+	s.skipSpace()
+	sreal, simag := s.complexTokens()
 	real := atof(s, sreal)
 	imag := atof(s, simag)
 	return cmplx(real, imag)
@@ -503,7 +579,7 @@ func (s *ss) convertString(verb int) string {
 	return s.token() // %s and %v just return the next word
 }
 
-// quotedString returns the double- or back-quoted string.
+// quotedString returns the double- or back-quoted string represented by the next input characters.
 func (s *ss) quotedString() string {
 	quote := s.mustGetRune()
 	switch quote {
@@ -593,15 +669,20 @@ const floatVerbs = "eEfFgGv"
 
 // scanOne scans a single value, deriving the scanner from the type of the argument.
 func (s *ss) scanOne(verb int, field interface{}) {
+	s.buf.Reset()
 	var err os.Error
 	// If the parameter has its own Scan method, use that.
 	if v, ok := field.(Scanner); ok {
-		err = v.Scan(s)
+		err = v.Scan(s, verb)
 		if err != nil {
 			s.error(err)
 		}
 		return
 	}
+	if !s.widPresent {
+		s.maxWid = 1 << 30 // Huge
+	}
+	s.wid = 0
 	switch v := field.(type) {
 	case *bool:
 		*v = s.scanBool(verb)
@@ -637,15 +718,18 @@ func (s *ss) scanOne(verb int, field interface{}) {
 	// scan in high precision and convert, in order to preserve the correct error condition.
 	case *float:
 		if s.okVerb(verb, floatVerbs, "float") {
-			*v = float(s.convertFloat(s.token()))
+			s.skipSpace()
+			*v = float(s.convertFloat(s.floatToken()))
 		}
 	case *float32:
 		if s.okVerb(verb, floatVerbs, "float32") {
-			*v = float32(s.convertFloat32(s.token()))
+			s.skipSpace()
+			*v = float32(s.convertFloat32(s.floatToken()))
 		}
 	case *float64:
 		if s.okVerb(verb, floatVerbs, "float64") {
-			*v = s.convertFloat64(s.token())
+			s.skipSpace()
+			*v = s.convertFloat64(s.floatToken())
 		}
 	case *string:
 		*v = s.convertString(verb)
@@ -699,11 +783,14 @@ func (s *ss) scanOne(verb int, field interface{}) {
 				v.Elem(i).(*reflect.Uint8Value).Set(str[i])
 			}
 		case *reflect.FloatValue:
-			v.Set(float(s.convertFloat(s.token())))
+			s.skipSpace()
+			v.Set(float(s.convertFloat(s.floatToken())))
 		case *reflect.Float32Value:
-			v.Set(float32(s.convertFloat(s.token())))
+			s.skipSpace()
+			v.Set(float32(s.convertFloat(s.floatToken())))
 		case *reflect.Float64Value:
-			v.Set(s.convertFloat(s.token()))
+			s.skipSpace()
+			v.Set(s.convertFloat(s.floatToken()))
 		case *reflect.ComplexValue:
 			v.Set(complex(s.scanComplex(verb, (*ss).convertFloat)))
 		case *reflect.Complex64Value:
@@ -823,7 +910,9 @@ func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err os.E
 		}
 		i++ // % is one byte
 
-		// TODO: FLAGS
+		// do we have 20 (width)?
+		s.maxWid, s.widPresent, i = parsenum(format, i, end)
+
 		c, w := utf8.DecodeRuneInString(format[i:])
 		i += w
 
@@ -836,5 +925,8 @@ func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err os.E
 		s.scanOne(c, field)
 		numProcessed++
 	}
+	if numProcessed < len(a) {
+		s.errorString("too many operands")
+	}
 	return
 }

src/pkg/fmt/scan_test.go

@@ -26,6 +26,14 @@ type ScanfTest struct {
 	out    interface{}
 }
 
+type ScanfMultiTest struct {
+	format string
+	text   string
+	in     []interface{}
+	out    []interface{}
+	err    string
+}
+
 type (
 	renamedBool       bool
 	renamedInt        int
@@ -65,6 +73,7 @@ var (
 	float32Val           float32
 	float64Val           float64
 	stringVal            string
+	stringVal1           string
 	bytesVal             []byte
 	complexVal           complex
 	complex64Val         complex64
@@ -91,17 +100,29 @@ var (
 	renamedComplex128Val renamedComplex128
 )
 
-// Xs accepts any non-empty run of x's.
-var xPat = testing.MustCompile("x+")
-
+// Xs accepts any non-empty run of the verb character
 type Xs string
 
-func (x *Xs) Scan(state ScanState) os.Error {
-	tok, err := state.Token()
+func (x *Xs) Scan(state ScanState, verb int) os.Error {
+	var tok string
+	var c int
+	var err os.Error
+	wid, present := state.Width()
+	if !present {
+		tok, err = state.Token()
+	} else {
+		for i := 0; i < wid; i++ {
+			c, err = state.GetRune()
+			if err != nil {
+				break
+			}
+			tok += string(c)
+		}
+	}
 	if err != nil {
 		return err
 	}
-	if !xPat.MatchString(tok) {
+	if !testing.MustCompile(string(verb) + "+").MatchString(tok) {
 		return os.ErrorString("syntax error for xs")
 	}
 	*x = Xs(tok)
@@ -169,7 +190,7 @@ var scanTests = []ScanTest{
 	ScanTest{"115\n", &renamedBytesVal, renamedBytes([]byte("115"))},
 
 	// Custom scanner.
-	ScanTest{"  xxx ", &xVal, Xs("xxx")},
+	ScanTest{"  vvv ", &xVal, Xs("vvv")},
 }
 
 var scanfTests = []ScanfTest{
@@ -178,7 +199,7 @@ var scanfTests = []ScanfTest{
 	ScanfTest{"%v", "-71\n", &intVal, -71},
 	ScanfTest{"%d", "72\n", &intVal, 72},
 	ScanfTest{"%d", "73\n", &int8Val, int8(73)},
-	ScanfTest{"%d", "-74\n", &int16Val, int16(-74)},
+	ScanfTest{"%d", "+74\n", &int16Val, int16(74)},
 	ScanfTest{"%d", "75\n", &int32Val, int32(75)},
 	ScanfTest{"%d", "76\n", &int64Val, int64(76)},
 	ScanfTest{"%b", "1001001\n", &intVal, 73},
@@ -236,7 +257,12 @@ var scanfTests = []ScanfTest{
 	ScanfTest{"here is\tthe value:%d", "here is   the\tvalue:118\n", &intVal, 118},
 	ScanfTest{"%% %%:%d", "% %:119\n", &intVal, 119},
 
+	// Corner cases
 	ScanfTest{"%x", "FFFFFFFF\n", &uint32Val, uint32(0xFFFFFFFF)},
+
+	// Custom scanner.
+	ScanfTest{"%s", "  sss ", &xVal, Xs("sss")},
+	ScanfTest{"%2s", "sssss", &xVal, Xs("ss")},
 }
 
 var overflowTests = []ScanTest{
@@ -253,6 +279,34 @@ var overflowTests = []ScanTest{
 	ScanTest{"(1-1e500i)", &complex128Val, 0},
 }
 
+var i, j, k int
+var f float
+var s, t string
+var c complex
+var x, y Xs
+
+func args(a ...interface{}) []interface{} { return a }
+
+var multiTests = []ScanfMultiTest{
+	ScanfMultiTest{"", "", nil, nil, ""},
+	ScanfMultiTest{"%d", "23", args(&i), args(23), ""},
+	ScanfMultiTest{"%2s%3s", "22333", args(&s, &t), args("22", "333"), ""},
+	ScanfMultiTest{"%2d%3d", "44555", args(&i, &j), args(44, 555), ""},
+	ScanfMultiTest{"%2d.%3d", "66.777", args(&i, &j), args(66, 777), ""},
+	ScanfMultiTest{"%d, %d", "23, 18", args(&i, &j), args(23, 18), ""},
+	ScanfMultiTest{"%3d22%3d", "33322333", args(&i, &j), args(333, 333), ""},
+	ScanfMultiTest{"%6vX=%3fY", "3+2iX=2.5Y", args(&c, &f), args((3 + 2i), float(2.5)), ""},
+	ScanfMultiTest{"%d%s", "123abc", args(&i, &s), args(123, "abc"), ""},
+
+	// Custom scanner.
+	ScanfMultiTest{"%2e%f", "eefffff", []interface{}{&x, &y}, []interface{}{Xs("ee"), Xs("fffff")}, ""},
+
+	// Errors
+	ScanfMultiTest{"%t", "23 18", []interface{}{&i}, nil, "bad verb"},
+	ScanfMultiTest{"%d %d %d", "23 18", []interface{}{&i, &j}, []interface{}{23, 18}, "too few operands"},
+	ScanfMultiTest{"%d %d", "23 18 27", []interface{}{&i, &j, &k}, []interface{}{23, 18}, "too many operands"},
+}
+
 func testScan(t *testing.T, scan func(r io.Reader, a ...interface{}) (int, os.Error)) {
 	for _, test := range scanTests {
 		r := strings.NewReader(test.text)
@@ -323,40 +377,59 @@ func TestScanOverflow(t *testing.T) {
 	}
 }
 
-func TestScanMultiple(t *testing.T) {
-	text := "1 2 3"
-	r := strings.NewReader(text)
-	var a, b, c, d int
-	n, err := Fscan(r, &a, &b, &c)
-	if n != 3 {
-		t.Errorf("Fscan count error: expected 3: got %d", n)
-	}
+// TODO: there's no conversion from []T to ...T, but we can fake it.  These
+// functions do the faking.  We index the table by the length of the param list.
+var scanf = []func(string, string, []interface{}) (int, os.Error){
+	0: func(s, f string, i []interface{}) (int, os.Error) { return Sscanf(s, f) },
+	1: func(s, f string, i []interface{}) (int, os.Error) { return Sscanf(s, f, i[0]) },
+	2: func(s, f string, i []interface{}) (int, os.Error) { return Sscanf(s, f, i[0], i[1]) },
+	3: func(s, f string, i []interface{}) (int, os.Error) { return Sscanf(s, f, i[0], i[1], i[2]) },
+}
+
+func TestScanfMulti(t *testing.T) {
+	sliceType := reflect.Typeof(make([]interface{}, 1)).(*reflect.SliceType)
+	for _, test := range multiTests {
+		n, err := scanf[len(test.in)](test.text, test.format, test.in)
 		if err != nil {
-		t.Errorf("Fscan expected no error scanning %q; got %s", text, err)
+			if test.err == "" {
+				t.Errorf("got error scanning (%q, %q): %q", test.format, test.text, err)
+			} else if strings.Index(err.String(), test.err) < 0 {
+				t.Errorf("got wrong error scanning (%q, %q): %q; expected %q", test.format, test.text, err, test.err)
 			}
-	text = "1 2 3 x"
-	r = strings.NewReader(text)
-	n, err = Fscan(r, &a, &b, &c, &d)
-	if n != 3 {
-		t.Errorf("Fscan count error: expected 3: got %d", n)
+			continue
 		}
-	if err == nil {
-		t.Errorf("Fscan expected error scanning %q", text)
+		if test.err != "" {
+			t.Errorf("expected error %q error scanning (%q, %q)", test.err, test.format, test.text)
+		}
+		if n != len(test.out) {
+			t.Errorf("count error on entry (%q, %q): expected %d got %d", test.format, test.text, len(test.out), n)
+			continue
+		}
+		// Convert the slice of pointers into a slice of values
+		resultVal := reflect.MakeSlice(sliceType, n, n)
+		for i := 0; i < n; i++ {
+			v := reflect.NewValue(test.in[i]).(*reflect.PtrValue).Elem()
+			resultVal.Elem(i).(*reflect.InterfaceValue).Set(v)
 		}
-	text = "1 2 3 x"
-	r = strings.NewReader(text)
-	n, err = Fscanf(r, "%d %d %d\n", &a, &b, &c, &d)
-	if n != 3 {
-		t.Errorf("Fscanf count error: expected 3: got %d", n)
+		result := resultVal.Interface()
+		if !reflect.DeepEqual(result, test.out) {
+			t.Errorf("scanning (%q, %q): expected %v got %v", test.format, test.text, test.out, result)
 		}
-	text = "1 2"
-	r = strings.NewReader(text)
-	n, err = Fscanf(r, "%d %d %d\n", &a, &b, &c, &d)
+	}
+}
+
+func TestScanMultiple(t *testing.T) {
+	var a int
+	var s string
+	n, err := Sscan("123abc", &a, &s)
 	if n != 2 {
-		t.Errorf("Fscanf count error: expected 2: got %d", n)
+		t.Errorf("Sscan count error: expected 2: got %d", n)
 	}
-	if err == nil {
-		t.Errorf("Fscanf expected error scanning %q", text)
+	if err != nil {
+		t.Errorf("Sscan expected no error; got %s", err)
+	}
+	if a != 123 || s != "abc" {
+		t.Errorf("Sscan wrong values: got (%d %q) expected (123 \"abc\")", a, s)
 	}
 }