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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2011, 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 */
/*! \file subcomplex/nsnappedtwosphere.h
* \brief Deals with 2-spheres made from two snapped 3-balls in a
* triangulation.
*/
#ifndef __NSNAPPEDTWOSPHERE_H
#ifndef __DOXYGEN
#define __NSNAPPEDTWOSPHERE_H
#endif
#include "regina-core.h"
#include "subcomplex/nsnappedball.h"
namespace regina {
class NTetrahedron;
class NTriangulation;
class NSnappedBall;
/**
* \weakgroup subcomplex
* @{
*/
/**
* Represents a 2-sphere made from two snapped 3-balls in a triangulation.
* This occurs when two snapped 3-balls are glued together at their
* equators (note that this gluing does not have to extend to faces). Each
* 3-ball has a central disc (bounded by the 3-ball's equator and bisecting
* its internal edge), and these two discs together form an embedded
* 2-sphere in the triangulation.
*
* This 2-sphere can be cut along and the two resulting 2-sphere
* boundaries filled in with 3-balls, and the resulting triangulation has
* the same number of tetrahedra as the original. If the snapped
* 2-sphere was separating, the resulting triangulation will contain the
* two terms of the corresponding connected sum.
*/
class REGINA_API NSnappedTwoSphere : public ShareableObject {
private:
NSnappedBall* ball[2];
/**< The two snapped 3-balls whose equators are joined. */
public:
/**
* Destroys this snapped 2-sphere; note that the corresponding
* snapped 3-balls will also be destroyed.
*/
virtual ~NSnappedTwoSphere();
/**
* Returns a newly created clone of this structure.
*
* @return a newly created clone.
*/
NSnappedTwoSphere* clone() const;
/**
* Returns one of the two snapped 3-balls whose equators are
* joined.
*
* @param index specifies which of the two 3-balls to return;
* this must be either 0 or 1.
* @return the corresponding snapped 3-ball.
*/
const NSnappedBall* getSnappedBall(int index) const;
/**
* Determines if the two given tetrahedra together form a snapped
* 2-sphere.
*
* \pre The two given tetrahedra are distinct.
*
* @param tet1 the first tetrahedron to examine.
* @param tet2 the second tetrahedron to examine.
* @return a newly created structure containing details of the
* snapped 2-sphere, or \c null if the given tetrahedra do not
* form a snapped 2-sphere.
*/
static NSnappedTwoSphere* formsSnappedTwoSphere(NTetrahedron* tet1,
NTetrahedron* tet2);
/**
* Determines if the two given snapped 3-balls together form a snapped
* 2-sphere.
*
* If this is the case, the snapped 3-balls stored in
* the structure returned will be clones of the
* original 3-balls, not the original 3-balls themselves.
*
* \pre The two given snapped 3-balls use distinct tetrahedra.
*
* @param ball1 the first snapped 3-ball to examine.
* @param ball2 the second snapped 3-ball to examine.
* @return a newly created structure containing details of the
* snapped 2-sphere, or \c null if the given snapped 3-balls do not
* form a snapped 2-sphere.
*/
static NSnappedTwoSphere* formsSnappedTwoSphere(NSnappedBall* ball1,
NSnappedBall* ball2);
void writeTextShort(std::ostream& out) const;
private:
/**
* Creates a new uninitialised structure.
*/
NSnappedTwoSphere();
};
/*@}*/
// Inline functions for NSnappedTwoSphere
inline NSnappedTwoSphere::NSnappedTwoSphere() {
}
inline NSnappedTwoSphere::~NSnappedTwoSphere() {
delete ball[0]; delete ball[1];
}
inline const NSnappedBall* NSnappedTwoSphere::getSnappedBall(int index) const {
return ball[index];
}
inline void NSnappedTwoSphere::writeTextShort(std::ostream& out) const {
out << "Snapped 2-sphere";
}
} // namespace regina
#endif
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