Numworks Epsilon  1.4.1
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s_modf.c
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1 /* @(#)s_modf.c 5.1 93/09/24 */
2 /*
3  * ====================================================
4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5  *
6  * Developed at SunPro, a Sun Microsystems, Inc. business.
7  * Permission to use, copy, modify, and distribute this
8  * software is freely granted, provided that this notice
9  * is preserved.
10  * ====================================================
11  */
12 
13 /*
14  * modf(double x, double *iptr)
15  * return fraction part of x, and return x's integral part in *iptr.
16  * Method:
17  * Bit twiddling.
18  *
19  * Exception:
20  * No exception.
21  */
22 
23 #include "math.h"
24 #include "math_private.h"
25 
26 static const double one = 1.0;
27 
28 double
29 modf(double x, double *iptr)
30 {
31  int32_t i0,i1,j0;
32  u_int32_t i;
33  EXTRACT_WORDS(i0,i1,x);
34  j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
35  if(j0<20) { /* integer part in high x */
36  if(j0<0) { /* |x|<1 */
37  INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
38  return x;
39  } else {
40  i = (0x000fffff)>>j0;
41  if(((i0&i)|i1)==0) { /* x is integral */
42  u_int32_t high;
43  *iptr = x;
44  GET_HIGH_WORD(high,x);
45  INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
46  return x;
47  } else {
48  INSERT_WORDS(*iptr,i0&(~i),0);
49  return x - *iptr;
50  }
51  }
52  } else if (j0>51) { /* no fraction part */
53  u_int32_t high;
54  *iptr = x*one;
55  GET_HIGH_WORD(high,x);
56  INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
57  return x;
58  } else { /* fraction part in low x */
59  i = ((u_int32_t)(0xffffffff))>>(j0-20);
60  if((i1&i)==0) { /* x is integral */
61  u_int32_t high;
62  *iptr = x;
63  GET_HIGH_WORD(high,x);
64  INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
65  return x;
66  } else {
67  INSERT_WORDS(*iptr,i0,i1&(~i));
68  return x - *iptr;
69  }
70  }
71 }
GET_HIGH_WORD
#define GET_HIGH_WORD(i, d)
Definition: math_private.h:269
one
#define one
Definition: k_tan.c:68
u_int32_t
uint32_t u_int32_t
Definition: types.h:10
EXTRACT_WORDS
#define EXTRACT_WORDS(ix0, ix1, d)
Definition: math_private.h:259
INSERT_WORDS
#define INSERT_WORDS(d, ix0, ix1)
Definition: math_private.h:287
modf
double modf(double x, double *iptr)
Definition: s_modf.c:29
int32_t
signed int int32_t
Definition: stdint.h:11
math_private.h