gonzui

    1: /*      $OpenBSD: s_clogf.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: /*                                                      clogf.c
   19:  *
   20:  *      Complex natural logarithm
   21:  *
   22:  *
   23:  *
   24:  * SYNOPSIS:
   25:  *
   26:  * void clogf();
   27:  * cmplxf z, w;
   28:  *
   29:  * clogf( &z, &w );
   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:  *    IEEE      -10,+10     30000       1.9e-6       6.2e-8
   50:  *
   51:  * Larger relative error can be observed for z near 1 +i0.
   52:  * In IEEE arithmetic the peak absolute error is 3.1e-7.
   53:  *
   54:  */
   55: 
   56: #include <complex.h>
   57: #include <math.h>
   58: 
   59: float complex
   60: clogf(float complex z)
   61: {
   62:         float complex w;
   63:         float p, rr, x, y;
   64: 
   65:         x = crealf(z);
   66:         y = cimagf(z);
   67:         rr = atan2f(y, x);
   68:         p = cabsf(z);
   69:         p = logf(p);
   70:         w = p + rr * I;
   71:         return (w);
   72: }