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/* @(#)z_pow.c 1.0 98/08/13 */
 
/*
FUNCTION
        <<pow>>, <<powf>>---x to the power y
INDEX
        pow
INDEX
        powf
 
 
ANSI_SYNOPSIS
        #include <math.h>
        double pow(double <[x]>, double <[y]>);
        float pow(float <[x]>, float <[y]>);
 
TRAD_SYNOPSIS
        #include <math.h>
        double pow(<[x]>, <[y]>);
        double <[x]>, <[y]>;
 
        float pow(<[x]>, <[y]>);
        float <[x]>, <[y]>;
 
DESCRIPTION
        <<pow>> and <<powf>> calculate <[x]> raised to the exponent <[y]>.
        @tex
        (That is, $x^y$.)
        @end tex
 
RETURNS
        On success, <<pow>> and <<powf>> return the value calculated.
 
        When the argument values would produce overflow, <<pow>>
        returns <<HUGE_VAL>> and set <<errno>> to <<ERANGE>>.  If the
        argument <[x]> passed to <<pow>> or <<powf>> is a negative
        noninteger, and <[y]> is also not an integer, then <<errno>>
        is set to <<EDOM>>.  If <[x]> and <[y]> are both 0, then
        <<pow>> and <<powf>> return <<1>>.
 
        You can modify error handling for these functions using <<matherr>>.
 
PORTABILITY
        <<pow>> is ANSI C. <<powf>> is an extension.  */
 
#include <float.h>
#include "fdlibm.h"
#include "zmath.h"
 
#ifndef _DOUBLE_IS_32BITS
 
double pow (double x, double y)
{
  double d, k, t, r = 1.0;
  int n, sign, exponent_is_even_int = 0;
  __uint32_t px;
 
  GET_HIGH_WORD (px, x);
 
  k = modf (y, &d);
 
  if (k == 0.0)
    {
      /* Exponent y is an integer. */
      if (modf (ldexp (y, -1), &t))
        {
          /* y is odd. */
          exponent_is_even_int = 0;
        }
      else
        {
          /* y is even. */
          exponent_is_even_int = 1;
        }
    }
 
  if (x == 0.0)
    {
      if (y <= 0.0)
        errno = EDOM;
    }
  else if ((t = y * log (fabs (x))) >= BIGX)
    {
      errno = ERANGE;
      if (px & 0x80000000)
        {
          /* x is negative. */
          if (k)
            {
              /* y is not an integer. */
              errno = EDOM;
              x = 0.0;
            }
          else if (exponent_is_even_int)
            x = z_infinity.d;
          else
            x = -z_infinity.d;
        }
      else
        {
          x = z_infinity.d;
        }
    }
  else if (t < SMALLX)
    {
      errno = ERANGE;
      x = 0.0;
    }
  else
    {
      if ( !k && fabs(d) <= 32767 )
        {
          n = (int) d;
 
          if ((sign = (n < 0)))
            n = -n;
 
          while ( n > 0 )
            {
              if ((unsigned int) n % 2)
                r *= x;
              x *= x;
              n = (unsigned int) n / 2;
            }
 
          if (sign)
            r = 1.0 / r;
 
          return r;
        }
      else
        {
          if ( px & 0x80000000 )
            {
              /* x is negative. */
              if ( k )
                {
                  /* y is not an integer. */
                  errno = EDOM;
                  return 0.0;
                }
            }
 
          x = exp (t);
 
          if (!exponent_is_even_int)
            {
              if (px & 0x80000000)
                {
                  /* y is an odd integer, and x is negative,
                     so the result is negative. */
                  GET_HIGH_WORD (px, x);
                  px |= 0x80000000;
                  SET_HIGH_WORD (x, px);
                }
            }
        }
    }
 
  return x;
}
 
#endif _DOUBLE_IS_32BITS

Line No.	Rev	Author	Line
1	148	jeremybenn
2			`/* @(#)z_pow.c 1.0 98/08/13 */`
3
4			`/*`
5			`FUNCTION`
6			`<<pow>>, <<powf>>---x to the power y`
7			`INDEX`
8			`pow`
9			`INDEX`
10			`powf`
11
12
13			`ANSI_SYNOPSIS`
14			`#include <math.h>`
15			`double pow(double <[x]>, double <[y]>);`
16			`float pow(float <[x]>, float <[y]>);`
17
18			`TRAD_SYNOPSIS`
19			`#include <math.h>`
20			`double pow(<[x]>, <[y]>);`
21			`double <[x]>, <[y]>;`
22
23			`float pow(<[x]>, <[y]>);`
24			`float <[x]>, <[y]>;`
25
26			`DESCRIPTION`
27			`<<pow>> and <<powf>> calculate <[x]> raised to the exponent <[y]>.`
28			`@tex`
29			`(That is, $x^y$.)`
30			`@end tex`
31
32			`RETURNS`
33			`On success, <<pow>> and <<powf>> return the value calculated.`
34
35			`When the argument values would produce overflow, <<pow>>`
36			`returns <<HUGE_VAL>> and set <<errno>> to <<ERANGE>>. If the`
37			`argument <[x]> passed to <<pow>> or <<powf>> is a negative`
38			`noninteger, and <[y]> is also not an integer, then <<errno>>`
39			`is set to <<EDOM>>. If <[x]> and <[y]> are both 0, then`
40			`<<pow>> and <<powf>> return <<1>>.`
41
42			`You can modify error handling for these functions using <<matherr>>.`
43
44			`PORTABILITY`
45			`<<pow>> is ANSI C. <<powf>> is an extension. */`
46
47			`#include <float.h>`
48			`#include "fdlibm.h"`
49			`#include "zmath.h"`
50
51			`#ifndef _DOUBLE_IS_32BITS`
52
53			`double pow (double x, double y)`
54			`{`
55			`double d, k, t, r = 1.0;`
56			`int n, sign, exponent_is_even_int = 0;`
57			`__uint32_t px;`
58
59			`GET_HIGH_WORD (px, x);`
60
61			`k = modf (y, &d);`
62
63			`if (k == 0.0)`
64			`{`
65			`/* Exponent y is an integer. */`
66			`if (modf (ldexp (y, -1), &t))`
67			`{`
68			`/* y is odd. */`
69			`exponent_is_even_int = 0;`
70			`}`
71			`else`
72			`{`
73			`/* y is even. */`
74			`exponent_is_even_int = 1;`
75			`}`
76			`}`
77
78			`if (x == 0.0)`
79			`{`
80			`if (y <= 0.0)`
81			`errno = EDOM;`
82			`}`
83			`else if ((t = y * log (fabs (x))) >= BIGX)`
84			`{`
85			`errno = ERANGE;`
86			`if (px & 0x80000000)`
87			`{`
88			`/* x is negative. */`
89			`if (k)`
90			`{`
91			`/* y is not an integer. */`
92			`errno = EDOM;`
93			`x = 0.0;`
94			`}`
95			`else if (exponent_is_even_int)`
96			`x = z_infinity.d;`
97			`else`
98			`x = -z_infinity.d;`
99			`}`
100			`else`
101			`{`
102			`x = z_infinity.d;`
103			`}`
104			`}`
105			`else if (t < SMALLX)`
106			`{`
107			`errno = ERANGE;`
108			`x = 0.0;`
109			`}`
110			`else`
111			`{`
112			`if ( !k && fabs(d) <= 32767 )`
113			`{`
114			`n = (int) d;`
115
116			`if ((sign = (n < 0)))`
117			`n = -n;`
118
119			`while ( n > 0 )`
120			`{`
121			`if ((unsigned int) n % 2)`
122			`r *= x;`
123			`x *= x;`
124			`n = (unsigned int) n / 2;`
125			`}`
126
127			`if (sign)`
128			`r = 1.0 / r;`
129
130			`return r;`
131			`}`
132			`else`
133			`{`
134			`if ( px & 0x80000000 )`
135			`{`
136			`/* x is negative. */`
137			`if ( k )`
138			`{`
139			`/* y is not an integer. */`
140			`errno = EDOM;`
141			`return 0.0;`
142			`}`
143			`}`
144
145			`x = exp (t);`
146
147			`if (!exponent_is_even_int)`
148			`{`
149			`if (px & 0x80000000)`
150			`{`
151			`/* y is an odd integer, and x is negative,`
152			`so the result is negative. */`
153			`GET_HIGH_WORD (px, x);`
154			`px \|= 0x80000000;`
155			`SET_HIGH_WORD (x, px);`
156			`}`
157			`}`
158			`}`
159			`}`
160
161			`return x;`
162			`}`
163
164			`#endif _DOUBLE_IS_32BITS`

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[/] [openrisc/] [trunk/] [gnu-old/] [newlib-1.17.0/] [newlib/] [libm/] [mathfp/] [s_pow.c] - Blame information for rev 816