1 /* $NetBSD: clog.c,v 1.1 2007/08/20 16:01:35 drochner Exp $ */
2
3 /*-
4 * Copyright (c) 2007 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software written by Stephen L. Moshier.
8 * It is redistributed by the NetBSD Foundation by permission of the author.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 *
31 * imported and modified include for newlib 2010/10/03
32 * Marco Atzeri <marco_atzeri@yahoo.it>
33 */
34
35 /*
36 FUNCTION
37 <<clog>>, <<clogf>>---complex base-e logarithm
38
39 INDEX
40 clog
41 INDEX
42 clogf
43
44 SYNOPSIS
45 #include <complex.h>
46 double complex clog(double complex <[z]>);
47 float complex clogf(float complex <[z]>);
48
49
50 DESCRIPTION
51 These functions compute the complex natural (base-<[e]>) logarithm
52 of <[z]>, with a branch cut along the negative real axis.
53
54 <<clogf>> is identical to <<clog>>, except that it performs
55 its calculations on <<floats complex>>.
56
57 RETURNS
58 @ifnottex
59 The clog functions return the complex natural logarithm value, in
60 the range of a strip mathematically unbounded along the real axis
61 and in the interval [-i*pi , +i*pi] along the imaginary axis.
62 @end ifnottex
63 @tex
64 The clog functions return the complex natural logarithm value, in
65 the range of a strip mathematically unbounded along the real axis
66 and in the interval [$-i\pi$, $+i\pi$] along the imaginary axis.
67 @end tex
68
69 PORTABILITY
70 <<clog>> and <<clogf>> are ISO C99
71
72 QUICKREF
73 <<clog>> and <<clogf>> are ISO C99
74
75 */
76
77 #include <complex.h>
78 #include <math.h>
79
80 double complex
clog(double complex z)81 clog(double complex z)
82 {
83 double complex w;
84 double p, rr;
85
86 rr = cabs(z);
87 p = log(rr);
88 rr = atan2(cimag(z), creal(z));
89 w = p + rr * (double complex) I;
90 return w;
91 }
92
