I hope the following example explains a little how to use incidence matrices. polytope > $M=new IncidenceMatrix([[0,1,2],[0,2,3],[0,1,19]]); polytope > print $M; {0 1 2} {0 2 3} {0 1 19} polytope > print $M->rows(); 3 polytope > print $M->cols(); 20 Now, the following gives an error. polytope > prin...