1 // Copyright 2009 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 math
6 7 // Frexp breaks f into a normalized fraction
8 // and an integral power of two.
9 // It returns frac and exp satisfying f == frac × 2**exp,
10 // with the absolute value of frac in the interval [½, 1).
11 //
12 // Special cases are:
13 //
14 // Frexp(±0) = ±0, 0
15 // Frexp(±Inf) = ±Inf, 0
16 // Frexp(NaN) = NaN, 0
17 func Frexp(f float64) (frac float64, exp int) {
18 if haveArchFrexp {
19 return archFrexp(f)
20 }
21 return frexp(f)
22 }
23 24 func frexp(f float64) (frac float64, exp int) {
25 // special cases
26 switch {
27 case f == 0:
28 return f, 0 // correctly return -0
29 case IsInf(f, 0) || IsNaN(f):
30 return f, 0
31 }
32 f, exp = normalize(f)
33 x := Float64bits(f)
34 exp += int((x>>shift)&mask) - bias + 1
35 x &^= mask << shift
36 x |= (-1 + bias) << shift
37 frac = Float64frombits(x)
38 return
39 }
40