## 9.3.78 ISNAN (X)

Description: | Tests whether IEEE real (S_floating and T_floating) numbers are Not-a-Number (NaN) values. On OpenVMS systems, the compiler option specifying IEEE floating format must be set.
Class: | Elemental function; Generic
Arguments: | X must be of type real.
Results: | The result is of type default logical. The result is .TRUE. if X is an IEEE NaN; otherwise, the result is .FALSE..

Examples

Consider the following:

      LOGICAL A
      DOUBLE PRECISION B
      ...
      A = ISNAN(B)

A is assigned the value .TRUE. if B is an IEEE NaN; otherwise, the value assigned is .FALSE..

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