Hi,

I did as you suggested. Here are the error messages:

polytope > print matroidal(edge_directions($PC->GRAPH, $p->VERTICES));
polymake: WARNING: Compiling temporary shared module, please be patient...
{"app": "polytope", "embed": "edge_directions.cc",
"inst": [
{"args": ["void", "perl::Canned ...

Hi,

I have just updated my version of Polymake, and the above code no longer works. I get the following error (after running the line print matroidal(edge_directions($PC->GRAPH, $p->VERTICES));):

polymake: ERROR: C++/perl Interface module compilation failed; most likely due to a type mismatch.
Set ...

Ah, sorry. In my own code I had been using simplicial complexes when a polyhedral complex was needed. Sorry for the confusion.

Thank you so much for your help!

I will just make one remark that if the subdivision is not a triangulation then one instead needs to use a polyhedral complex. Otherwise, extra edges will be added when Polymake makes a simplicial complex and these will likely not be of the form e_i-e_j. An example ...

One last question: If I wanted to check whether a regular subdivision was matroidal or not, how would I do this? Is there a property like EDGE_DIRECTIONS which I could apply to the subdivision (or the simplicial complex coming from the subdivision)?

Thanks for the reply. I have never written any subroutines in perl and am not very familiar with the language. I wrote the following attempt at a solution:


sub matroidal {
my @M = shift(@_);
my $bool = 1;
foreach @vector (@M) {
if (scalar(grep {$_ =~ 1} @vector) ==1) {
if (scalar(grep {$_ =~ -1 ...

A theorem by [GGMS] says that a polytope with vertices in \{0,1\}^n is a matroid polytope if and only if every edge of the polytope is parallel to e_i - e_j for some i and j .

My question is, has this been implemented somewhere in polymake? Specifically, I would like to be able to ask if a polytope ...