NULL— Function that returns an disassociated pointer
If MOLD is present, a disassociated pointer of the same type is returned, otherwise the type is determined by context.
In Fortran 95, MOLD is optional. Please note that Fortran 2003
includes cases where it is required.
PTR => NULL([MOLD])
|MOLD||(Optional) shall be a pointer of any association
status and of any type.
REAL, POINTER, DIMENSION(:) :: VEC => NULL ()