frexp.c

一个C源代码分析器

/* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <ansidecl.h>
#include <errno.h>
#include <math.h>

/* Break VALUE into a normalized fraction and an integral power of 2.  */
double
DEFUN(frexp, (value, exp), double value AND int *exp)
{
#ifdef	NAN
  if (__isinf (value))
    {
      errno = EDOM;
      *exp = 0;
      return __copysign (NAN, value);
    }
#endif

  if (__isnan (value))
    {
      errno = EDOM;
      *exp = 0;
      return value;
    }

  if (value == 0)
    {
      *exp = 0;
      return value;
    }

  /* Add one to the exponent of the number,
     so we have one digit before the binary point.  */
  *exp = (int) __logb (value) + 1;
  return ldexp (value, - *exp);
}