mirror of
https://github.com/autc04/Retro68.git
synced 2024-11-28 05:51:04 +00:00
141 lines
2.9 KiB
C
141 lines
2.9 KiB
C
|
|
/* @(#)z_atangentf.c 1.0 98/08/13 */
|
|
/******************************************************************
|
|
* The following routines are coded directly from the algorithms
|
|
* and coefficients given in "Software Manual for the Elementary
|
|
* Functions" by William J. Cody, Jr. and William Waite, Prentice
|
|
* Hall, 1980.
|
|
******************************************************************/
|
|
/******************************************************************
|
|
* Arctangent
|
|
*
|
|
* Input:
|
|
* x - floating point value
|
|
*
|
|
* Output:
|
|
* arctangent of x
|
|
*
|
|
* Description:
|
|
* This routine calculates arctangents.
|
|
*
|
|
*****************************************************************/
|
|
|
|
#include <float.h>
|
|
#include "fdlibm.h"
|
|
#include "zmath.h"
|
|
|
|
static const float ROOT3 = 1.732050807;
|
|
static const float a[] = { 0.0, 0.523598775, 1.570796326,
|
|
1.047197551 };
|
|
static const float q[] = { 0.1412500740e+1 };
|
|
static const float p[] = { -0.4708325141, -0.5090958253e-1 };
|
|
|
|
float
|
|
_DEFUN (atangentf, (float, float, float, int),
|
|
float x _AND
|
|
float v _AND
|
|
float u _AND
|
|
int arctan2)
|
|
{
|
|
float f, g, R, P, Q, A, res;
|
|
int N;
|
|
int branch = 0;
|
|
int expv, expu;
|
|
|
|
/* Preparation for calculating arctan2. */
|
|
if (arctan2)
|
|
{
|
|
if (u == 0.0)
|
|
if (v == 0.0)
|
|
{
|
|
errno = ERANGE;
|
|
return (z_notanum_f.f);
|
|
}
|
|
else
|
|
{
|
|
branch = 1;
|
|
res = __PI_OVER_TWO;
|
|
}
|
|
|
|
if (!branch)
|
|
{
|
|
int e;
|
|
/* Get the exponent values of the inputs. */
|
|
g = frexpf (v, &expv);
|
|
g = frexpf (u, &expu);
|
|
|
|
/* See if a divide will overflow. */
|
|
e = expv - expu;
|
|
if (e > FLT_MAX_EXP)
|
|
{
|
|
branch = 1;
|
|
res = __PI_OVER_TWO;
|
|
}
|
|
|
|
/* Also check for underflow. */
|
|
else if (e < FLT_MIN_EXP)
|
|
{
|
|
branch = 2;
|
|
res = 0.0;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!branch)
|
|
{
|
|
if (arctan2)
|
|
f = fabsf (v / u);
|
|
else
|
|
f = fabsf (x);
|
|
|
|
if (f > 1.0)
|
|
{
|
|
f = 1.0 / f;
|
|
N = 2;
|
|
}
|
|
else
|
|
N = 0;
|
|
|
|
if (f > (2.0 - ROOT3))
|
|
{
|
|
A = ROOT3 - 1.0;
|
|
f = (((A * f - 0.5) - 0.5) + f) / (ROOT3 + f);
|
|
N++;
|
|
}
|
|
|
|
/* Check for values that are too small. */
|
|
if (-z_rooteps_f < f && f < z_rooteps_f)
|
|
res = f;
|
|
|
|
/* Calculate the Taylor series. */
|
|
else
|
|
{
|
|
g = f * f;
|
|
P = (p[1] * g + p[0]) * g;
|
|
Q = g + q[0];
|
|
R = P / Q;
|
|
|
|
res = f + f * R;
|
|
}
|
|
|
|
if (N > 1)
|
|
res = -res;
|
|
|
|
res += a[N];
|
|
}
|
|
|
|
if (arctan2)
|
|
{
|
|
if (u < 0.0)
|
|
res = __PI - res;
|
|
if (v < 0.0)
|
|
res = -res;
|
|
}
|
|
else if (x < 0.0)
|
|
{
|
|
res = -res;
|
|
}
|
|
|
|
return (res);
|
|
}
|