is_connex - connectivity test
is_connex returns 1 if the graph g is connected and 0 otherwise.
g=make_graph('foo',1,3,[1,2,3,1],[2,3,1,3]); is_connex(g) g=make_graph('foo',1,4,[1,2,3,1],[2,3,1,3]); is_connex(g)