anchor.diff:    ! Get the grid identifier for the given variable.
     function get_var_grid(self, var_name, grid_id) result(status)
       type (heat_model), intent (in) :: self
  -    character (len=*), pointer, intent (in) :: var_name
  +    character (len=*), intent (in) :: var_name
       integer, intent (out) :: grid_id
       integer :: status
   
  
positive.code:   ! Get a reference to the values (flattened!) of the given variable.
    function get_value_ref(self, var_name, dest) result(status)
      type (heat_model), intent (in) :: self
      character (len=*), pointer, intent (in) :: var_name
      real, pointer, intent (inout) :: dest(:)
      integer :: status
  
  
negative.code:   ! Get memory use per array element, in bytes.
    function get_var_itemsize(self, var_name, size) result(status)
      type (heat_model), intent (in) :: self
      character (len=*), intent (in) :: var_name
      integer, intent (out) :: size
      integer :: status
  
  