gonzui

    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
   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
   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: }