There exist different ways to store a triangulation within a data structure. One could represent a triangulation as a list (array) of edges. However, this does not provide the direct information about the neighbour edges of a given edge. Edge Flip algorithm needs this information together with the edge connecting the third vertices of the two incident triangles. Quad edge data structure provides all necessary information for a given edge. Guibas and Stolfi proposed this data structure and discussed it together with its topological operators in great detail [7].