# Source file src/math/bits.go

```     1  // Copyright 2009 The Go Authors. All rights reserved.
2  // Use of this source code is governed by a BSD-style
4
5  package math
6
7  const (
8  	uvnan    = 0x7FF8000000000001
9  	uvinf    = 0x7FF0000000000000
10  	uvneginf = 0xFFF0000000000000
11  	uvone    = 0x3FF0000000000000
13  	shift    = 64 - 11 - 1
14  	bias     = 1023
15  	signMask = 1 << 63
16  	fracMask = 1<<shift - 1
17  )
18
19  // Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
21  	var v uint64
22  	if sign >= 0 {
23  		v = uvinf
24  	} else {
25  		v = uvneginf
26  	}
27  	return Float64frombits(v)
28  }
29
30  // NaN returns an IEEE 754 “not-a-number” value.
31  func NaN() float64 { return Float64frombits(uvnan) }
32
33  // IsNaN reports whether f is an IEEE 754 “not-a-number” value.
34  func IsNaN(f float64) (is bool) {
35  	// IEEE 754 says that only NaNs satisfy f != f.
36  	// To avoid the floating-point hardware, could use:
37  	//	x := Float64bits(f);
38  	//	return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
39  	return f != f
40  }
41
42  // IsInf reports whether f is an infinity, according to sign.
43  // If sign > 0, IsInf reports whether f is positive infinity.
44  // If sign < 0, IsInf reports whether f is negative infinity.
45  // If sign == 0, IsInf reports whether f is either infinity.
47  	// Test for infinity by comparing against maximum float.
48  	// To avoid the floating-point hardware, could use:
49  	//	x := Float64bits(f);
50  	//	return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
51  	return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64
52  }
53
54  // normalize returns a normal number y and exponent exp
55  // satisfying x == y × 2**exp. It assumes x is finite and non-zero.
56  func normalize(x float64) (y float64, exp int) {
57  	const SmallestNormal = 2.2250738585072014e-308 // 2**-1022
58  	if Abs(x) < SmallestNormal {
59  		return x * (1 << 52), -52
60  	}
61  	return x, 0
62  }
63
```

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