1 // Copyright 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 runtime
6 7 // inf2one returns a signed 1 if f is an infinity and a signed 0 otherwise.
8 // The sign of the result is the sign of f.
9 func inf2one(f float64) float64 {
10 g := 0.0
11 if isInf(f) {
12 g = 1.0
13 }
14 return copysign(g, f)
15 }
16 17 func complex64div(n complex64, m complex64) complex64 {
18 return complex64(complex128div(complex128(n), complex128(m)))
19 }
20 21 func complex128div(n complex128, m complex128) complex128 {
22 var e, f float64 // complex(e, f) = n/m
23 24 // Algorithm for robust complex division as described in
25 // Robert L. Smith: Algorithm 116: Complex division. Commun. ACM 5(8): 435 (1962).
26 if abs(real(m)) >= abs(imag(m)) {
27 ratio := imag(m) / real(m)
28 denom := real(m) + ratio*imag(m)
29 e = (real(n) + imag(n)*ratio) / denom
30 f = (imag(n) - real(n)*ratio) / denom
31 } else {
32 ratio := real(m) / imag(m)
33 denom := imag(m) + ratio*real(m)
34 e = (real(n)*ratio + imag(n)) / denom
35 f = (imag(n)*ratio - real(n)) / denom
36 }
37 38 if isNaN(e) && isNaN(f) {
39 // Correct final result to infinities and zeros if applicable.
40 // Matches C99: ISO/IEC 9899:1999 - G.5.1 Multiplicative operators.
41 42 a, b := real(n), imag(n)
43 c, d := real(m), imag(m)
44 45 switch {
46 case m == 0 && (!isNaN(a) || !isNaN(b)):
47 e = copysign(inf, c) * a
48 f = copysign(inf, c) * b
49 50 case (isInf(a) || isInf(b)) && isFinite(c) && isFinite(d):
51 a = inf2one(a)
52 b = inf2one(b)
53 e = inf * (a*c + b*d)
54 f = inf * (b*c - a*d)
55 56 case (isInf(c) || isInf(d)) && isFinite(a) && isFinite(b):
57 c = inf2one(c)
58 d = inf2one(d)
59 e = 0 * (a*c + b*d)
60 f = 0 * (b*c - a*d)
61 }
62 }
63 64 return complex(e, f)
65 }
66