ISNAN — Test for a NaN

Description

ISNAN tests whether a floating-point value is an IEEE Not-a-Number (NaN).

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

Standard

GNU extension

Class

Elemental function