frexp(3C)            COMPATIBILITY FUNCTIONS            frexp(3C)



NAME
     frexp, ldexp, logb, modf, modff, nextafter, scalb -  manipu-
     late parts of floating-point numbers

SYNOPSIS
     #include <math.h>

     double frexp (double value, int *eptr);

     double ldexp (double value, int exp);

     double logb (double value);

     double nextafter (double value1, double value2);

     double scalb (double value, double exp);

     double modf (double value, double *iptr);

     float modff (float value, float *iptr);

DESCRIPTION
     Every non-zero number can be  written  uniquely  as  x*  2n,
     where  the  ``mantissa''  (fraction) x is in the range 0.5 <
     |x| < 1.0, and the ``exponent''  n  is  an  integer.   frexp
     returns  the  mantissa  of  a  double  value, and stores the
     exponent indirectly in the location pointed to by eptr.   If
     value is zero, both results returned by frexp are zero.

     ldexp and scalb return the quantity value* 2exp.   The  only
     difference  between the two is that scalb of a signaling NaN
     will result in the invalid operation exception being raised.

     logb returns the unbiased  exponent  of  its  floating-point
     argument as a double-precision floating-point value.

     modf and modff (single-precision version) return the  signed
     fractional  part  of  value  and  store  the  integral  part
     indirectly in the location pointed to by iptr.

     nextafter returns the  next  representable  double-precision
     floating-point  value  following  value1 in the direction of
     value2.  Thus, if value2  is  less  than  value1,  nextafter
     returns the largest representable floating-point number less
     than value1.

SEE ALSO
     cc(1), intro(3M).

DIAGNOSTICS
     If ldexp would cause overflow, +HUGE (defined in math.h)  is
     returned  (according to the sign of value), and errno is set



          Last change: C Programming Language Utilities         1

frexp(3C)            COMPATIBILITY FUNCTIONS            frexp(3C)



     to ERANGE.  If ldexp would cause underflow, zero is returned
     and  errno is set to ERANGE.  If the input value to ldexp is
     NaN or infinity, that input is returned and errno is set  to
     EDOM.   The same error conditions apply to scalb except that
     a signaling NaN as input will result in the raising  of  the
     invalid operation exception.

     logb of NaN returns that NaN, logb of infinity returns posi-
     tive  infinity,  and  logb of zero returns negative infinity
     and results in the raising of the divide by zero  exception.
     In each of these conditions errno is set to EDOM.

     If input value1 to nextafter is positive or negative  infin-
     ity,  that  input is returned and errno is set to EDOM.  The
     overflow and inexact exceptions  are  signalled  when  input
     value1  is finite, but nextafter(value1, value2) is not. The
     underflow  and  inexact  exceptions   are   signalled   when
     nextafter(value1, value2) lies strictly between +2-1022.  In
     both cases errno is set to ERANGE.

     When the program is compiled with the cc options -Xc or -Xa,
     HUGE_VAL is returned instead of HUGE.

































          Last change: C Programming Language Utilities         2