# ISNAN

Elemental Intrinsic Function (Generic): Tests whether IEEE* real (binary32, binary64, and binary128) numbers are Not-a-Number (NaN) values.

result = ISNAN (x)

x | (Input) Must be of type real.

## Results

The result type is default logical. The result is .TRUE. if x is an IEEE NaN; otherwise, the result is .FALSE..

## Example

      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..

Parent topic: H to I