25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * CDDL HEADER START
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * The contents of this file are subject to the terms of the
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Common Development and Distribution License (the "License").
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * You may not use this file except in compliance with the License.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * or http://www.opensolaris.org/os/licensing.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * See the License for the specific language governing permissions
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25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Use is subject to license terms.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 1. Reduce y to positive by atan2(y,x)=-atan2(-y,x).
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 2. Reduce x to positive by (if x and y are unexceptional):
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ARG (x+iy) = arctan(y/x) ... if x > 0,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ARG (x+iy) = pi - arctan[y/(-x)] ... if x < 0,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Special cases:
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2((anything), NaN ) is NaN;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(NAN , (anything) ) is NaN;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-0, +(anything but NaN)) is +-0 ;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-0, -(anything but NaN)) is +-PI ;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-(anything but 0 and NaN), 0) is +-PI/2;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-(anything but INF and NaN), +INF) is +-0 ;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-(anything but INF and NaN), -INF) is +-PI;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-INF,+INF ) is +-PI/4 ;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-INF,-INF ) is +-3PI/4;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-PI/2;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * The hexadecimal values are the intended ones for the following constants.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * The decimal values may be used, provided that the compiler will convert
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * from decimal to binary accurately enough to produce the hexadecimal values
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtisstatic const long double
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis PI3o4 = 2.356194490192344928846982537459627163148L,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis PIo4 = 0.785398163397448309615660845819875721049L,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis PIo2 = 1.570796326794896619231321691639751442099L,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis PI = 3.141592653589793238462643383279502884197L,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis PI_lo = 8.671810130123781024797044026043351968762e-35L;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis long double t, z;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis if (x != x || y != y)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (x + y); /* return NaN if x or y is NAN */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* when y = 0 */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (y); /* atan(+0,+anything) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (y); /* atan(-0,+anything) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (PI + tiny); /* atan(+0,-anything) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (-PI - tiny); /* atan(-0,-anything) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* when x = 0 */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (signy == 1 ? -PIo2 - tiny : PIo2 + tiny);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* when x is INF */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (PIo4 + tiny); /* atan(+INF,+INF) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (-PIo4 - tiny); /* atan(-INF,+INF) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (PI3o4 + tiny); /* atan(+INF,-INF) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (-PI3o4 - tiny); /* atan(-INF,-INF) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (-PI - tiny); /* atan(-...,-INF) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* when y is INF */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (signy == 1 ? -PIo2 - tiny : PIo2 + tiny);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* compute y/x */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (z); /* atan(+,+) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (-z); /* atan(-,+) */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* NOTREACHED */