/*      $NetBSD: n_atan.c,v 1.8 2024/06/09 13:35:38 riastradh Exp $     */
/*
* Copyright (c) 1985, 1993
*      The Regents of the University of California.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#include <sys/cdefs.h>
__RCSID("$NetBSD: n_atan.c,v 1.8 2024/06/09 13:35:38 riastradh Exp $");

#ifndef lint
#if 0
static char sccsid[] = "@(#)atan.c      8.1 (Berkeley) 6/4/93";
#endif
#endif /* not lint */

/* ATAN(X)
* RETURNS ARC TANGENT OF X
* DOUBLE PRECISION (IEEE DOUBLE 53 bits, VAX D FORMAT 56 bits)
* CODED IN C BY K.C. NG, 4/16/85, REVISED ON 6/10/85.
*
* Required kernel function:
*      atan2(y,x)
*
* Method:
*      atan(x) = atan2(x,1.0).
*
* Special case:
*      if x is NaN, return x itself.
*
* Accuracy:
* 1)  If atan2() uses machine PI, then
*
*      atan(x) returns (PI/pi) * (the exact arc tangent of x) nearly rounded;
*      and PI is the exact pi rounded to machine precision (see atan2 for
*      details):
*
*      in decimal:
*              pi = 3.141592653589793 23846264338327 .....
*    53 bits   PI = 3.141592653589793 115997963 ..... ,
*    56 bits   PI = 3.141592653589793 227020265 ..... ,
*
*      in hexadecimal:
*              pi = 3.243F6A8885A308D313198A2E....
*    53 bits   PI = 3.243F6A8885A30  =  2 * 1.921FB54442D18    error=.276ulps
*    56 bits   PI = 3.243F6A8885A308 =  4 * .C90FDAA22168C2    error=.206ulps
*
*      In a test run with more than 200,000 random arguments on a VAX, the
*      maximum observed error in ulps (units in the last place) was
*      0.86 ulps.      (comparing against (PI/pi)*(exact atan(x))).
*
* 2)  If atan2() uses true pi, then
*
*      atan(x) returns the exact atan(x) with error below about 2 ulps.
*
*      In a test run with more than 1,024,000 random arguments on a VAX, the
*      maximum observed error in ulps (units in the last place) was
*      0.85 ulps.
*/

#include "namespace.h"

#include "mathimpl.h"

__weak_alias(atan, _atan)
__weak_alias(atanf, _atanf)

double
atan(double x)
{
       double one=1.0;
       return(atan2(x,one));
}

float
atanf(float x)
{
       float one=1.0;
       return (float)atan2(x,one);
}