anchor.diff:                     VTK_VAR_TEXT_R4    ! real(R4P)    vectorial (texture)
   endinterface
   !> @brief Function for saving mesh with different topologies in VTK-XML standard.
  -!> VTK_GEO_XML is an interface to 7 different functions; there are 2 functions for each of 3 topologies supported and a function
  -!> for closing XML pieces. VTK_GEO_XML must be called after VTK_INI_XML. It saves the mesh geometry. The inputs that must be passed
  +!> VTK_GEO_XML is an interface to 7 different functions, there are 2 functions for each of 3 topologies supported and a function
  +!> for closing XML pieces: one function for mesh coordinates with R8P precision and one for mesh coordinates with R4P precision.
  +!> @remark VTK_GEO_XML must be called after VTK_INI_XML. It saves the mesh geometry. The inputs that must be passed
   !> change depending on the topologies choiced. Not all VTK topologies have been implemented (\em polydata topologies are absent).
   !> @note The XML standard is more powerful than legacy. XML file can contain more than 1 mesh with its
   !> associated variables. Thus there is the necessity to close each \em pieces that compose the data-set saved in the
  
positive.code:                    VTK_GEO_RECT_R4    ! real(R4P) RECTILINEAR_GRID
  endinterface
  !> @brief Function for saving data variable(s) in VTK-legacy standard.
  !> VTK_VAR is an interface to 8 different functions; there are 3 functions for scalar variables, 3 functions for vectorial
  !> variables and 2 function texture variables.
  !> This function saves the data variables related to geometric mesh. The inputs that must be passed change depending on the data
  !> variables type.
  !> @note Examples of usage are: \n
  !> \b Scalar data calling: \n
  !>    E_IO=VTK_VAR(NN,'Sca',var); real(I4P):: var(1:NN) \n
  !> \b Vectorial data calling: \n
  !>    E_IO=VTK_VAR('vect',NN,'Vec',varX,varY,varZ); real(I4P):: varX(1:NN),varY(1:NN),varZ(1:NN).
  interface VTK_VAR
    module procedure VTK_VAR_SCAL_R8, & ! real(R8P)    scalar
                     VTK_VAR_SCAL_R4, & ! real(R4P)    scalar
  
negative.code:   !---------------------------------------------------------------------------------------------------------------------------------
    endfunction VTK_GEO_XML_CLOSEP
  
    !> Function that \b must be used when unstructured grid is used, it saves the connectivity of the unstructured gird.
    !> @note The vector \b connect must follow the VTK-legacy standard. It is passed as \em assumed-shape array
    !> because its dimensions is related to the mesh dimensions in a complex way. Its dimensions can be calculated by the following
    !> equation: \f$dc = dc = \sum\limits_{i = 1}^{NC} {nvertex_i }\f$.
    !> Note that this equation is different from the legacy one. The XML connectivity convention is quite different from the
    !> legacy standard. As an example suppose we have a mesh composed by 2 cells, one hexahedron (8 vertices) and one pyramid with
    !> square basis (5 vertices) and suppose that the basis of pyramid is constitute by a face of the hexahedron and so the two cells
    !> share 4 vertices. The above equation gives \f$dc=8+5=13\f$. The connectivity vector for this mesh can be: \n
    !> first cell \n
    !> connect(1)  = 0 identification flag of \f$1^\circ\f$ vertex of 1° cell \n
    !> connect(2)  = 1 identification flag of \f$2^\circ\f$ vertex of 1° cell \n
  