1 // Copyright 2009-2010 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 /*
8 Floating-point mod function.
9 */
10 11 // Mod returns the floating-point remainder of x/y.
12 // The magnitude of the result is less than y and its
13 // sign agrees with that of x.
14 //
15 // Special cases are:
16 //
17 // Mod(±Inf, y) = NaN
18 // Mod(NaN, y) = NaN
19 // Mod(x, 0) = NaN
20 // Mod(x, ±Inf) = x
21 // Mod(x, NaN) = NaN
22 func Mod(x, y float64) float64 {
23 if haveArchMod {
24 return archMod(x, y)
25 }
26 return mod(x, y)
27 }
28 29 func mod(x, y float64) float64 {
30 if y == 0 || IsInf(x, 0) || IsNaN(x) || IsNaN(y) {
31 return NaN()
32 }
33 y = Abs(y)
34 35 yfr, yexp := Frexp(y)
36 r := x
37 if x < 0 {
38 r = -x
39 }
40 41 for r >= y {
42 rfr, rexp := Frexp(r)
43 if rfr < yfr {
44 rexp = rexp - 1
45 }
46 r = r - Ldexp(y, rexp-yexp)
47 }
48 if x < 0 {
49 r = -r
50 }
51 return r
52 }
53