drem(3M)                       DG/UX R4.11MU05                      drem(3M)


NAME
       drem - IEEE floating-point remainder

SYNOPSIS
       #include <ieeefp.h>     /* for IEEE environment */

       or

       #include <math.h>       /* for System V environment */

       double drem (x,y)
       double x, y;

DESCRIPTION
       drem returns the remainder of x/y as specified by IEEE Standard 754
       for Binary Floating-Point Arithmetic.  The remainder r is calculated
       as

         r = x - n * y

       where n is the integer nearest the exact value of x/y.  If the
       absolute value of x/y is .5, then n is the even integer nearest the
       result of x/y.  Since the IEEE standard requires that the exact value
       of x/y be used in the calculation, the 'round nearest' rounding mode
       is in effect throughout the execution of the drem function.  The
       remainder is always considered to be exact, so inexact exceptions are
       never raised.

   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |             point     safe  |
                     +---------+-----------------------------+
                     |drem     |     Y         N        N    |
                     +---------+-----------------------------+
DIAGNOSTICS
       The IEEE standard defines drem(x, 0) and drem(infinity, y) to be
       invalid operations.  In addition, this implementation considers
       drem(x, y) to be an invalid operation when x/y results in infinity or
       double-precision overflow.  These operations raise an 'invalid
       operation' exception, which results in signal SIGFPE if traps are
       enabled and a NaN otherwise.

SEE ALSO
       reentrant(3), fpgetround(3C), isnan(3C).

BUGS
       This implementation of drem does not allow exceptional values to be
       fixed by a trap handler.


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