Imports an embedded plane graph read from ais into lcc.
Objects are added in lcc, existing darts are not modified.
Returns a dart created during the import.
Precondition:
LCC::dimension≥2 and LCC::ambient_dimension==2.
File format
The file format must be the following. First
the number of vertices and the number of edges of the planar graph.
Then, for each vertex of the planar graph, the coordinates of the
ith vertex (two numbers for x and y coordinates). The first
vertex index is 0. Then for each edge of the planar graph, the two
indices of the two vertices (two numbers between 0 and the number of
vertices minus 1).
Example of import_graph reading the above file as istream. Left: A planar graph embedded in the plane with
P0=(1.0,3.0), P1=(0.0,2.0), P2=(2.0,2.0), P3=(0.0,0.0), P4=(2.0,0.0).
Right: the 2D linear cell complex reconstructed.