anchor.diff:    real(R8P),                  intent(in)    :: y(1:) !< Y coordinates.
     real(R8P),                  intent(in)    :: z(1:) !< Z coordinates.
     integer(I4P)                              :: error !< Error status.
  -  !---------------------------------------------------------------------------------------------------------------------------------
  -
  -  !---------------------------------------------------------------------------------------------------------------------------------
  +
     if ((np/=size(x, dim=1)).or.(np/=size(y, dim=1)).or.(np/=size(z, dim=1))) then
       self%error = 1
       return
  
positive.code:     self%error = self%write_dataarray(data_name=data_name, x=[x], is_tuples=.true.)
    endselect
    error = self%error
    !---------------------------------------------------------------------------------------------------------------------------------
    endfunction write_fielddata1_rank0
  
    function write_fielddata_tag(self, action) result(error)
    !---------------------------------------------------------------------------------------------------------------------------------
    !< Write `<FieldData>`/`</FieldData>` start/end tag.
    !---------------------------------------------------------------------------------------------------------------------------------
    class(xml_writer_abstract), intent(inout) :: self      !< Writer.
    character(*),               intent(in)    :: action    !< Action: **open** or **close** tag.
    integer(I4P)                              :: error     !< Error status.
    type(string)                              :: action_   !< Action string.
    !---------------------------------------------------------------------------------------------------------------------------------
  
    !---------------------------------------------------------------------------------------------------------------------------------
    action_ = trim(adjustl(action)) ; action_ = action_%upper()
    select case(action_%chars())
    case('OPEN')
  
negative.code:     enddo
    endif
    error = self%error
    endfunction write_parallel_block_files_array
  
    function write_parallel_block_files_string(self, filenames, names, delimiter) result(error)
    !< Write list of files that belong to the current block (list passed as single string).
    !<
    !<#### Example of usage: 3 files blocks
  