usr/src/lib/libm/common/C/atan2pi.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  23  */
  24 /*
  25  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  26  * Use is subject to license terms.
  27  */
  28
  29 /*
  30  * atan2pi(x) = atan2(x)/pi
  31  */
  32
  33 #include "libm.h"
  34
  35 static const double invpi = 0.3183098861837906715377675;
  36
  37 double
  38 atan2pi(double y, double x) {
  39         int     ix, iy;
  40
  41         if (x == 0.0 && y == 0.0) {
  42                 ix = ((int *)&x)[HIWORD];
  43                 iy = ((int *)&y)[HIWORD];
  44                 if (ix >= 0)
  45                         return (y);
  46                 return ((iy >= 0)? 1.0 : -1.0);
  47         }
  48         return (atan2(y, x) * invpi);
  49 }