math/big: fix TestFloatSetFloat64String

A -0 constant is the same as 0. Use explicit negative zero
for float64 -0.0. Also, fix two test cases that were wrong.

Fixes #19673.

Change-Id: Ic09775f29d9bc2ee7814172e59c4a693441ea730
Reviewed-on: https://go-review.googlesource.com/38463
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/math/big/floatconv_test.go b/src/math/big/floatconv_test.go
index edcb2eb105026d15c6d2fce678075f437611c6a4..9911280abc26c1dab0fe230fe05697584ea994c7 100644 (file)
--- a/src/math/big/floatconv_test.go
+++ b/src/math/big/floatconv_test.go
@@ -12,6 +12,8 @@ import (
        "testing"
 )
 
+var zero_ float64
+
 func TestFloatSetFloat64String(t *testing.T) {
        inf := math.Inf(0)
        nan := math.NaN()
@@ -22,7 +24,7 @@ func TestFloatSetFloat64String(t *testing.T) {
        }{
                // basics
                {"0", 0},
-               {"-0", -0},
+               {"-0", -zero_},
                {"+0", 0},
                {"1", 1},
                {"-1", -1},
@@ -36,10 +38,10 @@ func TestFloatSetFloat64String(t *testing.T) {
 
                // various zeros
                {"0e100", 0},
-               {"-0e+100", 0},
+               {"-0e+100", -zero_},
                {"+0e-100", 0},
                {"0E100", 0},
-               {"-0E+100", 0},
+               {"-0E+100", -zero_},
                {"+0E-100", 0},
 
                // various decimal exponent formats
@@ -78,7 +80,7 @@ func TestFloatSetFloat64String(t *testing.T) {
 
                // decimal mantissa, binary exponent
                {"0p0", 0},
-               {"-0p0", -0},
+               {"-0p0", -zero_},
                {"1p10", 1 << 10},
                {"1p+10", 1 << 10},
                {"+1p-10", 1.0 / (1 << 10)},
@@ -88,9 +90,9 @@ func TestFloatSetFloat64String(t *testing.T) {
 
                // binary mantissa, decimal exponent
                {"0b0", 0},
-               {"-0b0", -0},
+               {"-0b0", -zero_},
                {"0b0e+10", 0},
-               {"-0b0e-10", -0},
+               {"-0b0e-10", -zero_},
                {"0b1010", 10},
                {"0B1010E2", 1000},
                {"0b.1", 0.5},
@@ -99,7 +101,7 @@ func TestFloatSetFloat64String(t *testing.T) {
 
                // binary mantissa, binary exponent
                {"0b0p+10", 0},
-               {"-0b0p-10", -0},
+               {"-0b0p-10", -zero_},
                {"0b.1010p4", 10},
                {"0b1p-1", 0.5},
                {"0b001p-3", 0.125},
@@ -108,9 +110,9 @@ func TestFloatSetFloat64String(t *testing.T) {
 
                // hexadecimal mantissa and exponent
                {"0x0", 0},
-               {"-0x0", -0},
+               {"-0x0", -zero_},
                {"0x0p+10", 0},
-               {"-0x0p-10", -0},
+               {"-0x0p-10", -zero_},
                {"0xff", 255},
                {"0X.8p1", 1},
                {"-0X0.00008p16", -0.5},
@@ -134,8 +136,8 @@ func TestFloatSetFloat64String(t *testing.T) {
                }
                f, _ := x.Float64()
                want := new(Float).SetFloat64(test.x)
-               if x.Cmp(want) != 0 {
-                       t.Errorf("%s: got %s (%v); want %v", test.s, &x, f, test.x)
+               if x.Cmp(want) != 0 || x.Signbit() != want.Signbit() {
+                       t.Errorf("%s: got %v (%v); want %v", test.s, &x, f, test.x)
                }
        }
 }