AIMA.Core.Logic.FOL.Inference.FOLModelElimination.tryCancellation C# (CSharp) Метод

        private Chain tryCancellation(Chain c)
        {
            Literal head = c.getHead();
            if (null != head && !(head is ReducedLiteral))
            {
                foreach (Literal l in c.getTail())
                {
                    if (l is ReducedLiteral)
                    {
                        // if they can be resolved
                        if (head.isNegativeLiteral() != l.isNegativeLiteral())
                        {
                            Dictionary<Variable, Term> subst = unifier.unify(head
                                    .getAtomicSentence(), l.getAtomicSentence());
                            if (null != subst)
                            {
                                // I have a cancellation
                                // Need to apply subst to all of the
                                // literals in the cancellation
                                List<Literal> cancLits = new List<Literal>();
                                foreach (Literal lfc in c.getTail())
                                {
                                    AtomicSentence a = (AtomicSentence)substVisitor
                                            .subst(subst, lfc.getAtomicSentence());
                                    cancLits.Add(lfc.newInstance(a));
                                }
                                Chain cancellation = new Chain(cancLits);
                                cancellation
                                        .setProofStep(new ProofStepChainCancellation(
                                                cancellation, c, subst));
                                return cancellation;
                            }
                        }
                    }
                }
            }
            return c;
        }