isnan(3C)                      DG/UX R4.11MU05                     isnan(3C)


NAME
       isnan, isnand, isnanf, isinf, finite, fpclass, unordered - determine
       type of floating-point number

SYNOPSIS
       int isnand (double dsrc);

       int isnanf (float fsrc);

       int isinf (double dsrc);

       int finite (double dsrc);

       fpclasst fpclass (double dsrc);

       int unordered (double dsrc1, double dsrc2);


       int isnan (double dsrc);

DESCRIPTION
       isnan, isnand, and isnanf return true (1) if the argument dsrc or
       fsrc is a NaN; otherwise they return false (0).  The functionality of
       isnan is identical to that of isnand.

       isnanf is implemented as a macro included in the ieeefp.h header
       file.

       isinf returns true (1) if the argument dsrc is infinity; otherwise it
       returns false (0).

       fpclass returns the class the dsrc belongs to.  The 10 possible
       classes are as follows:
              FPSNAN      signaling NaN
              FPQNAN      quiet NaN
              FPNINF      negative infinity
              FPPINF      positive infinity
              FPNDENORM   negative denormalized non-zero
              FPPDENORM   positive denormalized non-zero
              FPNZERO     negative zero
              FPPZERO     positive zero
              FPNNORM     negative normalized non-zero
              FPPNORM     positive normalized non-zero

       finite returns true (1) if the argument dsrc is neither infinity nor
       NaN; otherwise it returns false (0).

       unordered returns true (1) if one of its two arguments is unordered
       with respect to the other argument.  This is equivalent to reporting
       whether either argument is NaN.  If neither of the arguments is NaN,
       false (0) is returned.

       None of these routines generate any exception, even for signaling
       NaNs.


   Considerations for Threads Programming
                     +----------+-----------------------------+
                     |          |                      async- |
                     |function  | reentrant   cancel   cancel |
                     |          |             point     safe  |
                     +----------+-----------------------------+
                     |finite    |     Y         N        N    |
                     |fpclass   |     Y         N        N    |
                     |isinf     |     Y         N        N    |
                     |isnan     |     Y         N        N    |
                     |isnand    |     Y         N        N    |
                     |isnanf    |     Y         N        N    |
                     |unordered |     Y         N        N    |
                     +----------+-----------------------------+

SEE ALSO
       reentrant(3), fpgetround(3C), intro(3M).


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