1// Copyright 2017 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package runtime
6
7import "unsafe"
8
9var inf = float64frombits(0x7FF0000000000000)
10
11// isNaN reports whether f is an IEEE 754 “not-a-number” value.
12func isNaN(f float64) (is bool) {
13	// IEEE 754 says that only NaNs satisfy f != f.
14	return f != f
15}
16
17// isFinite reports whether f is neither NaN nor an infinity.
18func isFinite(f float64) bool {
19	return !isNaN(f - f)
20}
21
22// isInf reports whether f is an infinity.
23func isInf(f float64) bool {
24	return !isNaN(f) && !isFinite(f)
25}
26
27// abs returns the absolute value of x.
28//
29// Special cases are:
30//
31//	abs(±Inf) = +Inf
32//	abs(NaN) = NaN
33func abs(x float64) float64 {
34	const sign = 1 << 63
35	return float64frombits(float64bits(x) &^ sign)
36}
37
38// copysign returns a value with the magnitude
39// of x and the sign of y.
40func copysign(x, y float64) float64 {
41	const sign = 1 << 63
42	return float64frombits(float64bits(x)&^sign | float64bits(y)&sign)
43}
44
45// float64bits returns the IEEE 754 binary representation of f.
46func float64bits(f float64) uint64 {
47	return *(*uint64)(unsafe.Pointer(&f))
48}
49
50// float64frombits returns the floating point number corresponding
51// the IEEE 754 binary representation b.
52func float64frombits(b uint64) float64 {
53	return *(*float64)(unsafe.Pointer(&b))
54}
55