54 lines
1.3 KiB
Go
54 lines
1.3 KiB
Go
// Copyright 2017 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package runtime
|
|
|
|
import "unsafe"
|
|
|
|
var inf = float64frombits(0x7FF0000000000000)
|
|
|
|
// isNaN reports whether f is an IEEE 754 ``not-a-number'' value.
|
|
func isNaN(f float64) (is bool) {
|
|
// IEEE 754 says that only NaNs satisfy f != f.
|
|
return f != f
|
|
}
|
|
|
|
// isFinite reports whether f is neither NaN nor an infinity.
|
|
func isFinite(f float64) bool {
|
|
return !isNaN(f - f)
|
|
}
|
|
|
|
// isInf reports whether f is an infinity.
|
|
func isInf(f float64) bool {
|
|
return !isNaN(f) && !isFinite(f)
|
|
}
|
|
|
|
// Abs returns the absolute value of x.
|
|
//
|
|
// Special cases are:
|
|
// Abs(±Inf) = +Inf
|
|
// Abs(NaN) = NaN
|
|
func abs(x float64) float64 {
|
|
const sign = 1 << 63
|
|
return float64frombits(float64bits(x) &^ sign)
|
|
}
|
|
|
|
// copysign returns a value with the magnitude
|
|
// of x and the sign of y.
|
|
func copysign(x, y float64) float64 {
|
|
const sign = 1 << 63
|
|
return float64frombits(float64bits(x)&^sign | float64bits(y)&sign)
|
|
}
|
|
|
|
// Float64bits returns the IEEE 754 binary representation of f.
|
|
func float64bits(f float64) uint64 {
|
|
return *(*uint64)(unsafe.Pointer(&f))
|
|
}
|
|
|
|
// Float64frombits returns the floating point number corresponding
|
|
// the IEEE 754 binary representation b.
|
|
func float64frombits(b uint64) float64 {
|
|
return *(*float64)(unsafe.Pointer(&b))
|
|
}
|