NULL— Function that returns an disassociated pointer
If MOLD is present, a dissassociated pointer of the same type is returned, otherwise the type is determined by context.
In Fortran 95, MOLD is optional. Please note that F2003 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 ()