modf.c File Reference

#include "libm.h"
#include "libm_util.h"

Include dependency graph for modf.c:

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Functions
double	modf (double x, double *iptr)

Function Documentation

modf()

double modf	(	double	x,
		double *	iptr
	)

Definition at line 30 of file modf.c.

{
  /* modf splits the argument x into integer and fraction parts,
     each with the same sign as x. */
 
 
  long long xexp;
  unsigned long long ux, ax, mask;
 
  GET_BITS_DP64(x, ux);
  ax = ux & (~SIGNBIT_DP64);
 
  if (ax >= 0x4340000000000000)
    {
      /* abs(x) is either NaN, infinity, or >= 2^53 */
      if (ax > 0x7ff0000000000000)
        {
          /* x is NaN */
          *iptr = x;
          return x + x; /* Raise invalid if it is a signalling NaN */
        }
      else
        {
          /* x is infinity or large. Return zero with the sign of x */
          *iptr = x;
          PUT_BITS_DP64(ux & SIGNBIT_DP64, x);
          return x;
        }
    }
  else if (ax < 0x3ff0000000000000)
    {
      /* abs(x) < 1.0. Set iptr to zero with the sign of x
         and return x. */
      PUT_BITS_DP64(ux & SIGNBIT_DP64, *iptr);
      return x;
    }
  else
    {
      xexp = ((ux & EXPBITS_DP64) >> EXPSHIFTBITS_DP64) - EXPBIAS_DP64;
      /* Mask out the bits of x that we don't want */
      mask = 1;
      mask = (mask << (EXPSHIFTBITS_DP64 - xexp)) - 1;
      PUT_BITS_DP64(ux & ~mask, *iptr);
      return x - *iptr;
    }
 
}