compiler/stdc/math/s_clog.c

   1 /*      $OpenBSD: s_clog.c,v 1.6 2013/07/03 04:46:36 espie 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 /*                                                      clog.c
  19  *
  20  *      Complex natural logarithm
  21  *
  22  *
  23  *
  24  * SYNOPSIS:
  25  *
  26  * double complex clog();
  27  * double complex z, w;
  28  *
  29  * w = clog (z);
  30  *
  31  *
  32  *
  33  * DESCRIPTION:
  34  *
  35  * Returns complex logarithm to the base e (2.718...) of
  36  * the complex argument x.
  37  *
  38  * If z = x + iy, r = sqrt( x**2 + y**2 ),
  39  * then
  40  *       w = log(r) + i arctan(y/x).
  41  *
  42  * The arctangent ranges from -PI to +PI.
  43  *
  44  *
  45  * ACCURACY:
  46  *
  47  *                      Relative error:
  48  * arithmetic   domain     # trials      peak         rms
  49  *    DEC       -10,+10      7000       8.5e-17     1.9e-17
  50  *    IEEE      -10,+10     30000       5.0e-15     1.1e-16
  51  *
  52  * Larger relative error can be observed for z near 1 +i0.
  53  * In IEEE arithmetic the peak absolute error is 5.2e-16, rms
  54  * absolute error 1.0e-16.
  55  */
  56
  57 #include <float.h>
  58 #include <complex.h>
  59 #include "math.h"
  60
  61 double complex
  62 clog(double complex z)
  63 {
  64         double complex w;
  65         double p, rr;
  66
  67         /*rr = sqrt( z->r * z->r  +  z->i * z->i );*/
  68         rr = cabs(z);
  69         p = log(rr);
  70         rr = atan2 (cimag (z), creal (z));
  71         w = p + rr * I;
  72         return (w);
  73 }
  74
  75 #if     LDBL_MANT_DIG == DBL_MANT_DIG
  76 AROS_MAKE_ASM_SYM(typeof(clogl), clogl, AROS_CSYM_FROM_ASM_NAME(clogl), AROS_CSYM_FROM_ASM_NAME(clog));
  77 AROS_EXPORT_ASM_SYM(AROS_CSYM_FROM_ASM_NAME(clogl));
  78 #endif  /* LDBL_MANT_DIG == DBL_MANT_DIG */