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Source file src/runtime/float.go

Documentation: runtime

```     1  // Copyright 2017 The Go Authors. All rights reserved.
2  // Use of this source code is governed by a BSD-style
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  //	Abs(±Inf) = +Inf
31  //	Abs(NaN) = NaN
32  func abs(x float64) float64 {
33  	const sign = 1 << 63
34  	return float64frombits(float64bits(x) &^ sign)
35  }
36
37  // copysign returns a value with the magnitude
38  // of x and the sign of y.
39  func copysign(x, y float64) float64 {
40  	const sign = 1 << 63
41  	return float64frombits(float64bits(x)&^sign | float64bits(y)&sign)
42  }
43
44  // Float64bits returns the IEEE 754 binary representation of f.
45  func float64bits(f float64) uint64 {
46  	return *(*uint64)(unsafe.Pointer(&f))
47  }
48
49  // Float64frombits returns the floating point number corresponding
50  // the IEEE 754 binary representation b.
51  func float64frombits(b uint64) float64 {
52  	return *(*float64)(unsafe.Pointer(&b))
53  }
54
```

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