newlib/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  * imported and modified include for newlib 2010/10/03
  29  * Marco Atzeri <marco_atzeri@yahoo.it>
  30  */
  31
  32 /*
  33 FUNCTION
  34         <<cproj>>, <<cprojf>>--- Riemann sphere projection
  35
  36 INDEX
  37         cproj
  38 INDEX
  39         cprojf
  40
  41 SYNOPSIS
  42        #include <complex.h>
  43        double complex cproj(double complex <[z]>);
  44        float complex cprojf(float complex <[z]>);
  45
  46
  47 DESCRIPTION
  48         These functions compute a projection of <[z]> onto the Riemann
  49         sphere: <[z]> projects to <[z]> except that all complex infinities
  50         (even those with one infinite part and one NaN part) project
  51         to positive infinity on the real axis. If <[z]> has an infinite part,
  52         then <<cproj>>(<[z]>) is equivalent to
  53
  54                  INFINITY + I * copysign(0.0, cimag(z))
  55
  56         <<cprojf>> is identical to <<cproj>>, except that it performs
  57         its calculations on <<floats complex>>.
  58
  59 RETURNS
  60         The cproj functions return the value of the projection onto
  61         the Riemann sphere.
  62
  63 PORTABILITY
  64         <<cproj>> and <<cprojf>> are ISO C99
  65
  66 QUICKREF
  67         <<cproj>> and <<cprojf>> are ISO C99
  68
  69 */
  70
  71 #include <sys/cdefs.h>
  72 /*__RCSID("$NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $"); */
  73
  74 #include <complex.h>
  75 #include <math.h>
  76
  77 #include "../common/fdlibm.h"
  78
  79 /*
  80  * cproj(double complex z)
  81  *
  82  * These functions return the value of the projection (not stereographic!)
  83  * onto the Riemann sphere.
  84  *
  85  * z projects to z, except that all complex infinities (even those with one
  86  * infinite part and one NaN part) project to positive infinity on the real axis.
  87  * If z has an infinite part, then cproj(z) shall be equivalent to:
  88  *
  89  * INFINITY + I * copysign(0.0, cimag(z))
  90  */
  91 double complex
  92 cproj(double complex z)
  93 {
  94         double_complex w = { .z = z };
  95
  96         if (isinf(creal(z)) || isinf(cimag(z))) {
  97 #ifdef __INFINITY
  98                 REAL_PART(w) = __INFINITY;
  99 #else
 100                 REAL_PART(w) = INFINITY;
 101 #endif
 102                 IMAG_PART(w) = copysign(0.0, cimag(z));
 103         }
 104
 105         return (w.z);
 106 }