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/* Copyright (c) 1997-2024
Ewgenij Gawrilow, Michael Joswig, and the polymake team
Technische Universität Berlin, Germany
https://polymake.org
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version: http://www.gnu.org/licenses/gpl.txt.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
--------------------------------------------------------------------------------
*/
namespace polymake { namespace topaz {
template <typename Complex>
PowerSet<Int> k_skeleton(const Complex& C, const Int k)
{
PowerSet<Int> SK;
for (auto f_it = entire(C); !f_it.at_end(); ++f_it) {
// the k skeleton are all faces of dimension <= k.
if (f_it->size()<=k) {
// facets are either equal or none contains the other.
SK+=*f_it;
continue;
}
// the k skeleton a facet are all subsets of size k+1
for (auto s_it=entire(all_subsets_of_k(*f_it, k+1)); !s_it.at_end(); ++s_it) {
// facets are either equal or none contains the other.
SK+=*s_it;
}
}
if (SK.empty()) // the empty complex is represented as a single empty set
SK += Set<Int>();
return SK;
}
} }
// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
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