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/* @(#)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)
        {
          /* Get the exponent values of the inputs. */
          g = frexpf (v, &expv);
          g = frexpf (u, &expu);
 
          /* See if a divide will overflow. */
          if ((expv - expu) > DBL_MAX_EXP + 1022)
            {
               branch = 1;
               res = __PI_OVER_TWO;
            }
 
          /* Also check for underflow. */
          else if ((expv - expu) < - DBL_MIN_EXP - 1022)
            {
               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 && branch)
    {
      if (u < 0.0 || branch == 2)
        res = __PI - res;
      if (v < 0.0 || branch == 1)
        res = -res;
    }
  else if (x < 0.0)
    {
      res = -res;
    }
 
  return (res);
}

Line No.	Rev	Author	Line
1	56	joel
2			`/* @(#)z_atangentf.c 1.0 98/08/13 */`
3			`/******************************************************************`
4			`* The following routines are coded directly from the algorithms`
5			`* and coefficients given in "Software Manual for the Elementary`
6			`* Functions" by William J. Cody, Jr. and William Waite, Prentice`
7			`* Hall, 1980.`
8			`******************************************************************/`
9			`/******************************************************************`
10			`* Arctangent`
11			`*`
12			`* Input:`
13			`* x - floating point value`
14			`*`
15			`* Output:`
16			`* arctangent of x`
17			`*`
18			`* Description:`
19			`* This routine calculates arctangents.`
20			`*`
21			`*****************************************************************/`
22
23			`#include <float.h>`
24			`#include "fdlibm.h"`
25			`#include "zmath.h"`
26
27			`static const float ROOT3 = 1.732050807;`
28			`static const float a[] = { 0.0, 0.523598775, 1.570796326,`
29			`1.047197551 };`
30			`static const float q[] = { 0.1412500740e+1 };`
31			`static const float p[] = { -0.4708325141, -0.5090958253e-1 };`
32
33			`float`
34			`_DEFUN (atangentf, (float, float, float, int),`
35			`float x _AND`
36			`float v _AND`
37			`float u _AND`
38			`int arctan2)`
39			`{`
40			`float f, g, R, P, Q, A, res;`
41			`int N;`
42			`int branch = 0;`
43			`int expv, expu;`
44
45			`/* Preparation for calculating arctan2. */`
46			`if (arctan2)`
47			`{`
48			`if (u == 0.0)`
49			`if (v == 0.0)`
50			`{`
51			`errno = ERANGE;`
52			`return (z_notanum_f.f);`
53			`}`
54			`else`
55			`{`
56			`branch = 1;`
57			`res = __PI_OVER_TWO;`
58			`}`
59
60			`if (!branch)`
61			`{`
62			`/* Get the exponent values of the inputs. */`
63			`g = frexpf (v, &expv);`
64			`g = frexpf (u, &expu);`
65
66			`/* See if a divide will overflow. */`
67			`if ((expv - expu) > DBL_MAX_EXP + 1022)`
68			`{`
69			`branch = 1;`
70			`res = __PI_OVER_TWO;`
71			`}`
72
73			`/* Also check for underflow. */`
74			`else if ((expv - expu) < - DBL_MIN_EXP - 1022)`
75			`{`
76			`branch = 2;`
77			`res = 0.0;`
78			`}`
79			`}`
80			`}`
81
82			`if (!branch)`
83			`{`
84			`if (arctan2)`
85			`f = fabsf (v / u);`
86			`else`
87			`f = fabsf (x);`
88
89			`if (f > 1.0)`
90			`{`
91			`f = 1.0 / f;`
92			`N = 2;`
93			`}`
94			`else`
95			`N = 0;`
96
97			`if (f > (2.0 - ROOT3))`
98			`{`
99			`A = ROOT3 - 1.0;`
100			`f = (((A * f - 0.5) - 0.5) + f) / (ROOT3 + f);`
101			`N++;`
102			`}`
103
104			`/* Check for values that are too small. */`
105			`if (-z_rooteps_f < f && f < z_rooteps_f)`
106			`res = f;`
107
108			`/* Calculate the Taylor series. */`
109			`else`
110			`{`
111			`g = f * f;`
112			`P = (p[1] * g + p[0]) * g;`
113			`Q = g + q[0];`
114			`R = P / Q;`
115
116			`res = f + f * R;`
117			`}`
118
119			`if (N > 1)`
120			`res = -res;`
121
122			`res += a[N];`
123			`}`
124
125			`if (arctan2 && branch)`
126			`{`
127			`if (u < 0.0 \|\| branch == 2)`
128			`res = __PI - res;`
129			`if (v < 0.0 \|\| branch == 1)`
130			`res = -res;`
131			`}`
132			`else if (x < 0.0)`
133			`{`
134			`res = -res;`
135			`}`
136
137			`return (res);`
138			`}`

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[/] [or1k/] [branches/] [newlib/] [newlib/] [newlib/] [libm/] [mathfp/] [sf_atangent.c] - Blame information for rev 56