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			}
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			}
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	}
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	}
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	bool Manifold::collapse_precond(VertexIter v1, HalfEdgeIter h)
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	bool Manifold::collapse_precond(VertexIter v1, HalfEdgeIter h)
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	{
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		/* The goal of this (fiendishly complex) function is to test
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			 whether an edge is collapsible. The test is as follows.
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			 1. For the two vertices adjacent to the edge, we generate
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			 a list of all their neighbouring vertices. We then generate a
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			 list of the vertices that occur in both these lists. That is,
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			 we find all vertices connected by edges to both endpoints
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			 of the edge and store these in a list.
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			 2. For both faces incident on the edge, check whether they
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			 are triangular. If this is the case, the face will be removed,
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			 and it is ok that the the third vertex is connected to both
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			 endpoints. Thus the third vertex in such a face is removed
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			 from the list generated in 1.
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			 3. If the list is now empty, all is well. Otherwise, there
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			 would be a vertex in the new mesh with two edges connecting
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			 it to the same vertex. Return false.
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			 4. TETRAHEDRON TEST:
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			 If the valency of both vertices is
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			 three, and the incident faces are triangles, we also disallow
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			 the operation. Reason: It introduces a vertex of valency two
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			 and if the final two polygons incident on the vertices
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			 that are adjacent to the edge being collapsed are triangles, then
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			 the construction will collapse
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			 5. VALENCY 4 TEST:
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			 If a face adjacent to the edge being collapsed is a triangle,
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			 it will disappear, and the valency of the final vertex beloning to
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			 this edge will be reduced by one. Hence this valency should be at
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			 least 4. A valency three vertex will be reduced to a valency two
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			 vertex which is considered illegal.
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			 6. PREVENT MERGING HOLES:
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			 We do not want to collapse an edge if its end points are boundary
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			 vertices, but its two adjacent faces are not NULL faces, because
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			 in that case we create a vertex where two holes meet. A non manifold
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			 situation.
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	{
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		*/
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		VertexIter v2 = h->vert;
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		VertexIter v2 = h->vert;
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		std::vector<int> link1;
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		std::vector<int> link1;
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		VertexCirculator vc1(v1);
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		VertexCirculator vc1(v1);
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		for(;!vc1.end();++vc1)
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		for(;!vc1.end();++vc1)