ISNAN(3f)

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

AUTHOR

This information was taken from the GFortran documentation (https://gcc.gnu.org/onlinedocs/gcc-5.3.0/gfortran/) and converted to a manpage by AstroFloyd (http://astrofloyd.org).