The value definition class represents the information contained in a PIF valueList construct which may occur in an unstructured point list or an attribute. It holds the actual length of the value list and a generic pointer which points to an array object storing the point coordinates of a point list or attribute values.
Since GRS supports element-wise reading and writing of unstructured grids, the subhandle of the PIF value list and the current index of a value list entry being written must be present too in this class. This is necessary for the attribute holding the element types of a mixed-element unstructured grid, where one element type after the other is read from or written to the value list of the PIF attribute. A method, that appends an entry to an already existing value list takes care of these class members.
The main purpose of this class is the representation of an unstructured point list. All information necessary to represent this point list is now available on this level of the left branch of the GRS class hierarchy of Fig. 7.2: The point list name, the unit information, the value type information, and finally the value list with the point coordinate array. The most important method is the one iterating over the specific points of an unstructured point list, since this method called by the generic point list iteration method used in ptbInterpolateAttribute(), if the target grid is an unstructured grid, i.e. contains an unstructured point list.
The GRS library does not implement methods that support deletion or insertion of single points currently, since this functionality is not necessary to fulfill the two main purposes GRS was designed for, as stated at the beginning of this section. This functionality would also require a different representation of the point list coordinates, since an array structure is not adequate for single point operations. However, the real array object representing the actual point coordinates could be substituted by a data structure better suited for this kind of point manipulations, which must still provide an iteration method so that ptbInterpolateAttribute() can still be invoked on unstructured grids.