lib/libm/complex/cproj.c

   1 /*      $NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $       */
   2
   3 /*-
   4  * Copyright (c) 2010 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  26  * POSSIBILITY OF SUCH DAMAGE.
  27  */
  28 #include <sys/cdefs.h>
  29 __RCSID("$NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $");
  30
  31 #include <complex.h>
  32 #include <math.h>
  33
  34 #include "../src/math_private.h"
  35
  36 /*
  37  * cproj(double complex z)
  38  *
  39  * These functions return the value of the projection (not stereographic!)
  40  * onto the Riemann sphere.
  41  *
  42  * z projects to z, except that all complex infinities (even those with one
  43  * infinite part and one NaN part) project to positive infinity on the real axis.
  44  * If z has an infinite part, then cproj(z) shall be equivalent to:
  45  *
  46  * INFINITY + I * copysign(0.0, cimag(z))
  47  */
  48 double complex
  49 cproj(double complex z)
  50 {
  51         double_complex w = { .z = z };
  52
  53         if (isinf(creal(z) || isinf(cimag(z)))) {
  54 #ifdef __INFINITY
  55                 REAL_PART(w) = __INFINITY;
  56 #else
  57                 REAL_PART(w) = INFINITY;
  58 #endif
  59                 IMAG_PART(w) = copysign(0.0, cimag(z));
  60         }
  61
  62         return (w.z);
  63 }