fmt.Scan: accept Inf and NaN

Fixes #1308.

R=rsc, r2
CC=golang-dev
https://golang.org/cl/3280045

src/pkg/fmt/scan.go

@@ -546,8 +546,16 @@ func (s *ss) scanUint(verb int, bitSize int) uint64 {
 // we have at least some digits, but Atof will do that.
 func (s *ss) floatToken() string {
 	s.buf.Reset()
+	// NaN?
+	if s.accept("nN") && s.accept("aA") && s.accept("nN") {
+		return s.buf.String()
+	}
 	// leading sign?
 	s.accept(sign)
+	// Inf?
+	if s.accept("iI") && s.accept("nN") && s.accept("fF") {
+		return s.buf.String()
+	}
 	// digits?
 	for s.accept(decimalDigits) {
 	}

src/pkg/fmt/scan_test.go

@@ -8,6 +8,7 @@ import (
 	"bufio"
 	. "fmt"
 	"io"
+	"math"
 	"os"
 	"reflect"
 	"regexp"
@@ -80,6 +81,12 @@ var (
 	renamedComplex128Val renamedComplex128
 )
 
+type FloatTest struct {
+	text string
+	in   float64
+	out  float64
+}
+
 // Xs accepts any non-empty run of the verb character
 type Xs string
 
@@ -399,6 +406,57 @@ func TestScanOverflow(t *testing.T) {
 	}
 }
 
+func verifyNaN(str string, t *testing.T) {
+	var f float
+	var f32 float32
+	var f64 float64
+	text := str + " " + str + " " + str
+	n, err := Fscan(strings.NewReader(text), &f, &f32, &f64)
+	if err != nil {
+		t.Errorf("got error scanning %q: %s", text, err)
+	}
+	if n != 3 {
+		t.Errorf("count error scanning %q: got %d", text, n)
+	}
+	if !math.IsNaN(float64(f)) || !math.IsNaN(float64(f32)) || !math.IsNaN(f64) {
+		t.Errorf("didn't get NaNs scanning %q: got %g %g %g", text, f, f32, f64)
+	}
+}
+
+func TestNaN(t *testing.T) {
+	for _, s := range []string{"nan", "NAN", "NaN"} {
+		verifyNaN(s, t)
+	}
+}
+
+func verifyInf(str string, t *testing.T) {
+	var f float
+	var f32 float32
+	var f64 float64
+	text := str + " " + str + " " + str
+	n, err := Fscan(strings.NewReader(text), &f, &f32, &f64)
+	if err != nil {
+		t.Errorf("got error scanning %q: %s", text, err)
+	}
+	if n != 3 {
+		t.Errorf("count error scanning %q: got %d", text, n)
+	}
+	sign := 1
+	if str[0] == '-' {
+		sign = -1
+	}
+	if !math.IsInf(float64(f), sign) || !math.IsInf(float64(f32), sign) || !math.IsInf(f64, sign) {
+		t.Errorf("didn't get right Infs scanning %q: got %g %g %g", text, f, f32, f64)
+	}
+}
+
+
+func TestInf(t *testing.T) {
+	for _, s := range []string{"inf", "+inf", "-inf", "INF", "-INF", "+INF", "Inf", "-Inf", "+Inf"} {
+		verifyInf(s, t)
+	}
+}
+
 // 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 fscanf = []func(io.Reader, string, []interface{}) (int, os.Error){