NDF_VALID - Determine whether an NDF identifier is valid

Description:

The routine determines whether an NDF identifier is valid (i.e. associated with an NDF).

Invocation:

CALL NDF_VALID( INDF, VALID, STATUS )

Arguments:

INDF = INTEGER (Given)

Identifier to be tested.

VALID = LOGICAL (Returned)

Whether the identifier is valid.

STATUS = INTEGER (Given and Returned)

The global status.