1 /* $OpenBSD: s_ccosf.c,v 1.2 2010/07/18 18:42:26 guenther Exp $ */
2 /*
3 * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 /* ccosf()
19 *
20 * Complex circular cosine
21 *
22 *
23 *
24 * SYNOPSIS:
25 *
26 * void ccosf();
27 * cmplxf z, w;
28 *
29 * ccosf( &z, &w );
30 *
31 *
32 *
33 * DESCRIPTION:
34 *
35 * If
36 * z = x + iy,
37 *
38 * then
39 *
40 * w = cos x cosh y - i sin x sinh y.
41 *
42 *
43 *
44 * ACCURACY:
45 *
46 * Relative error:
47 * arithmetic domain # trials peak rms
48 * IEEE -10,+10 30000 1.8e-7 5.5e-8
49 */
50
51 #include <complex.h>
52 #include <math.h>
53
54 /* calculate cosh and sinh */
55
56 static void
_cchshf(float xx,float * c,float * s)57 _cchshf(float xx, float *c, float *s)
58 {
59 float x, e, ei;
60
61 x = xx;
62 if(fabsf(x) <= 0.5f) {
63 *c = coshf(x);
64 *s = sinhf(x);
65 }
66 else {
67 e = expf(x);
68 ei = 0.5f/e;
69 e = 0.5f * e;
70 *s = e - ei;
71 *c = e + ei;
72 }
73 }
74
75 float complex
ccosf(float complex z)76 ccosf(float complex z)
77 {
78 float complex w;
79 float ch, sh;
80
81 _cchshf( cimagf(z), &ch, &sh );
82 w = cosf( crealf(z) ) * ch + ( -sinf( crealf(z) ) * sh) * I;
83 return (w);
84 }
85