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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2008, Ben Burton *
* For further details contact Ben Burton (bab@debian.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 of the *
* License, or (at your option) any later version. *
* *
* 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. *
* *
* You should have received a copy of the GNU General Public *
* License along with this program; if not, write to the Free *
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, *
* MA 02110-1301, USA. *
* *
**************************************************************************/
/* end stub */
#include "algebra/nabeliangroup.h"
#include "manifold/nhandlebody.h"
#include "triangulation/nedge.h"
#include "triangulation/ntetrahedron.h"
#include "subcomplex/nlayeredchain.h"
namespace regina {
bool NLayeredChain::extendAbove() {
NTetrahedron* adj = top->getAdjacentTetrahedron(topVertexRoles[0]);
if (adj == bottom || adj == top || adj == 0)
return false;
if (adj != top->getAdjacentTetrahedron(topVertexRoles[3]))
return false;
// Check the gluings.
NPerm adjRoles = top->getAdjacentTetrahedronGluing(topVertexRoles[0]) *
topVertexRoles * NPerm(0, 1);
if (adjRoles != top->getAdjacentTetrahedronGluing(topVertexRoles[3]) *
topVertexRoles * NPerm(2, 3))
return false;
// We can extend the layered chain.
top = adj;
topVertexRoles = adjRoles;
index++;
return true;
}
bool NLayeredChain::extendBelow() {
NTetrahedron* adj = bottom->getAdjacentTetrahedron(bottomVertexRoles[1]);
if (adj == bottom || adj == top || adj == 0)
return false;
if (adj != bottom->getAdjacentTetrahedron(bottomVertexRoles[2]))
return false;
// Check the gluings.
NPerm adjRoles = bottom->getAdjacentTetrahedronGluing(bottomVertexRoles[1])
* bottomVertexRoles * NPerm(0, 1);
if (adjRoles != bottom->getAdjacentTetrahedronGluing(bottomVertexRoles[2])
* bottomVertexRoles * NPerm(2, 3))
return false;
// We can extend the layered chain.
bottom = adj;
bottomVertexRoles = adjRoles;
index++;
return true;
}
bool NLayeredChain::extendMaximal() {
bool changed = false;
while (extendAbove())
changed = true;
while (extendBelow())
changed = true;
return changed;
}
void NLayeredChain::reverse() {
NTetrahedron* tmp = top;
top = bottom;
bottom = tmp;
NPerm pTmp = topVertexRoles * NPerm(1, 0, 3, 2);
topVertexRoles = bottomVertexRoles * NPerm(1, 0, 3, 2);
bottomVertexRoles = pTmp;
}
void NLayeredChain::invert() {
topVertexRoles = topVertexRoles * NPerm(3, 2, 1, 0);
bottomVertexRoles = bottomVertexRoles * NPerm(3, 2, 1, 0);
}
NManifold* NLayeredChain::getManifold() const {
return new NHandlebody(index <= 1 ? 0 : 1, true);
}
NAbelianGroup* NLayeredChain::getHomologyH1() const {
NAbelianGroup* ans = new NAbelianGroup();
if (index > 1)
ans->addRank();
return ans;
}
} // namespace regina
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