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math/big: replace Float.NewInf with Float.SetInf for more consistent API

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Change-Id: I2a60ea4a196eef1af5d2aae6cc239c64bddb6fb2
Reviewed-on: https://go-review.googlesource.com/6301
Reviewed-by: Alan Donovan <adonovan@google.com>
This commit is contained in:
Robert Griesemer 2015-02-25 15:38:15 -08:00
parent 612dd6c262
commit c3dc78f301
2 changed files with 35 additions and 9 deletions
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17
src/math/big/float.go
View File

@ -82,12 +82,6 @@ const (
MaxPrec = math.MaxUint32 // largest (theoretically) supported precision; likely memory-limited
)
// NewInf returns a new infinite Float value with value +Inf (sign >= 0),
// or -Inf (sign < 0).
func NewInf(sign int) *Float {
return &Float{neg: sign < 0, exp: infExp}
}
// Accuracy describes the rounding error produced by the most recent
// operation that generated a Float value, relative to the exact value:
//
@ -633,6 +627,17 @@ func (z *Float) SetRat(x *Rat) *Float {
return z.Quo(&a, &b)
}
// SetInf sets z to the infinite Float +Inf for sign >= 0,
// or -Inf for sign < 0, and returns z. The precision of
// z is unchanged and the result is always Exact.
func (z *Float) SetInf(sign int) *Float {
z.acc = Exact
z.neg = sign < 0
z.mant = z.mant[:0]
z.exp = infExp
return z
}
// Set sets z to the (possibly rounded) value of x and returns z.
// If z's precision is 0, it is changed to the precision of x
// before setting z (and rounding will have no effect).

27
src/math/big/float_test.go
View File

@ -90,13 +90,13 @@ func TestFloatZeroValue(t *testing.T) {
}
func makeFloat(s string) *Float {
var x Float
if s == "Inf" || s == "+Inf" {
return NewInf(+1)
return x.SetInf(+1)
}
if s == "-Inf" {
return NewInf(-1)
return x.SetInf(-1)
}
var x Float
x.SetPrec(1000)
if _, ok := x.SetString(s); !ok {
panic(fmt.Sprintf("%q is not a valid float", s))
@ -694,6 +694,27 @@ func TestFloatSetRat(t *testing.T) {
}
}
func TestFloatSetInf(t *testing.T) {
var f Float
for _, test := range []struct {
sign int
prec uint
want string
}{
{0, 0, "+Inf"},
{100, 0, "+Inf"},
{-1, 0, "-Inf"},
{0, 10, "+Inf"},
{100, 20, "+Inf"},
{-1, 30, "-Inf"},
} {
x := f.SetPrec(test.prec).SetInf(test.sign)
if got := x.String(); got != test.want || x.Prec() != test.prec {
t.Errorf("SetInf(%d) = %s (prec = %d); want %s (prec = %d)", test.sign, got, x.Prec(), test.want, test.prec)
}
}
}
func TestFloatUint64(t *testing.T) {
for _, test := range []struct {
x string