# Source file src/runtime/float.go

```     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
5  package runtime
6
7  import "unsafe"
8
9  var inf = float64frombits(0x7FF0000000000000)
10
11  // isNaN reports whether f is an IEEE 754 “not-a-number” value.
12  func 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.
18  func isFinite(f float64) bool {
19  	return !isNaN(f - f)
20  }
21
22  // isInf reports whether f is an infinity.
23  func 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
33  func 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.
40  func 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.
46  func 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.
52  func float64frombits(b uint64) float64 {
53  	return *(*float64)(unsafe.Pointer(&b))
54  }
55
```

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