Lahey/GNU Fortran

Next: , Previous: ISHFTC, Up: Intrinsic Procedures


8.136 ISNAN — Test for a NaN

Description:
ISNAN tests whether a floating-point value is an IEEE Not-a-Number (NaN).
Standard:
GNU extension
Class:
Elemental function
Syntax:
ISNAN(X)
Arguments:

X Variable of the type REAL.

Return value:
Returns a default-kind LOGICAL. The returned value is TRUE if X is a NaN and FALSE otherwise.
Example:
          program test_nan
            implicit none
            real :: x
            x = -1.0
            x = sqrt(x)
            if (isnan(x)) stop '"x" is a NaN'
          end program test_nan