/usr/include/polymake/topaz/2D_tools.tcc is in libpolymake-dev-common 3.2r2-3.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | /* Copyright (c) 1997-2018
Ewgenij Gawrilow, Michael Joswig (Technische Universitaet Berlin, Germany)
http://www.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.
--------------------------------------------------------------------------------
*/
#include "polymake/topaz/hasse_diagram.h"
namespace polymake { namespace topaz {
// return values: 1=true, 0=false, -1=undef (does not occur here)
template <typename Complex, typename VertexSet>
int is_ball_or_sphere(const Complex& C, const GenericSet<VertexSet>& V, int_constant<2>)
{
graph::Lattice<graph::lattice::BasicDecoration> HD= hasse_diagram_from_facets(Array<Set<int> >(C));
// check whether C is a pseudo_manifold and compute the boundary B
std::list< Set<int> > B;
bool is_PM = is_pseudo_manifold(HD, true, std::back_inserter(B));
if (!is_PM) return 0;
// check whether B is a sphere or empty
const bool B_is_empty = B.empty();
if (!B_is_empty && is_ball_or_sphere(B, int_constant<1>())==0) return 0;
// S:= C + B*v for a vertex v not contained in C
// note: S is a sphere <=> C is ball or sphere
// check euler char of S
// if (B.empty()) S = -1 + #vert - #edges_of_C + #C
// else S = -1 + (#vert + 1) - (#edges_of_C + #B) + (#C + #B)
int euler_char= V.top().size() - HD.nodes_of_rank(HD.rank()-2).size() + C.size();
if (B_is_empty) --euler_char;
if (euler_char!=1) return 0;
return 1;
}
} }
// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
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