Compute the covering relation of an endorelation.
relation_cover(x)an endorelation.
Let \(R\) be an endorelation with domain \((X, X)\) and \(P\) be the asymmetric part of \(R\) for which \(x P y\) iff \(x R y\) and not \(y R x\). (If \(R\) is a \(\le\) order relation, \(P\) is the associated strict order.) We say that \(x\) is covered by \(y\) if \(x P y\) and there is no \(z\) such that \(x P z\) and \(z P y\). One also says that \(y\) covers \(x\), or that it is a successor of \(x\).
The covering relation of \(R\) consists of all pairs \((x, y)\) for which \(x\) is covered by \(y\).