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 // Modf returns integer and fractional floating-point numbers
8 // that sum to f. Both values have the same sign as f.
9 //
10 // Special cases are:
11 //
12 // Modf(±Inf) = ±Inf, NaN
13 // Modf(NaN) = NaN, NaN
14 func Modf(f float64) (int float64, frac float64) {
15 if haveArchModf {
16 return archModf(f)
17 }
18 return modf(f)
19 }
20 21 func modf(f float64) (int float64, frac float64) {
22 if f < 1 {
23 switch {
24 case f < 0:
25 int, frac = Modf(-f)
26 return -int, -frac
27 case f == 0:
28 return f, f // Return -0, -0 when f == -0
29 }
30 return 0, f
31 }
32 33 x := Float64bits(f)
34 e := uint(x>>shift)&mask - bias
35 36 // Keep the top 12+e bits, the integer part; clear the rest.
37 if e < 64-12 {
38 x &^= 1<<(64-12-e) - 1
39 }
40 int = Float64frombits(x)
41 frac = f - int
42 return
43 }
44