ISNAN

 ISNAN (real-number)

 Class:  Elemental function - Generic

 Tests whether IEEE REAL*4 (S_floating) and REAL*8 (T_floating)
 numbers are Not-a-Number (NaN) values.  To use this function,
 compiler option /FLOAT=IEEE_FLOAT must be set.

 +------+---------+----------+------------+-------------+        
 | Args | Generic | Specific |  Argument  | Result Type |
 +------+---------+----------+------------+-------------+
 |  1   |  ISNAN  |   --     | REAL*4     | LOGICAL*4   |
 |      |         |          | REAL*8     | LOGICAL*4   |
 +------+---------+----------+------------+-------------+