newlib/libm/complex/clog.c

   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
  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 * I;
  90         return w;
  91 }