blob: f2769d4fd754457594d92ccb6530050bc1bbff2c (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
// Copyright 2010 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 math
// Logb returns the binary exponent of x.
//
// Special cases are:
// Logb(±Inf) = +Inf
// Logb(0) = -Inf
// Logb(NaN) = NaN
func Logb(x float64) float64 {
// special cases
switch {
case x == 0:
return Inf(-1)
case IsInf(x, 0):
return Inf(1)
case IsNaN(x):
return x
}
return float64(ilogb(x))
}
// Ilogb returns the binary exponent of x as an integer.
//
// Special cases are:
// Ilogb(±Inf) = MaxInt32
// Ilogb(0) = MinInt32
// Ilogb(NaN) = MaxInt32
func Ilogb(x float64) int {
// special cases
switch {
case x == 0:
return MinInt32
case IsNaN(x):
return MaxInt32
case IsInf(x, 0):
return MaxInt32
}
return ilogb(x)
}
// logb returns the binary exponent of x. It assumes x is finite and
// non-zero.
func ilogb(x float64) int {
x, exp := normalize(x)
return int((Float64bits(x)>>shift)&mask) - bias + exp
}
|
