Example #1
0
        public void Visit(Atom atom)
        {
            Sequent sequent = new Sequent(
                new ISymbol[0],
                atom
                );

            Result = solver.Prove(sequent);
        }
Example #2
0
        public void Visit(Contradiction contradiction)
        {
            Sequent sequent = new Sequent(
                new ISymbol[0],
                contradiction
                );

            Result = solver.Prove(sequent);
        }
Example #3
0
        public void Visit(AND and)
        {
            Sequent sequent = new Sequent(
                new ISymbol[0],
                and
                );

            Result = solver.Prove(sequent);
        }
Example #4
0
        public Proof Prove(Sequent sequent)
        {
            if (proofStack.Contains(sequent.conclusion) && !AllowBypassProofStack(sequent.conclusion))
            {
                // We're already trying to prove this conclusion; circular argument detected
                return(null);
            }

            if (currentRule == RuleType.OR_Elimination)
            {
                orEliminationPremises.Push(currentOEPremise);
            }

            Proof proof = new Proof
            {
                conclusion = sequent.conclusion
            };
            var premiseSteps = proof.AddPremises(sequent.premises);

            proofStack.Push(sequent.conclusion);
            truths.AddAll(premiseSteps);

            RuleType[] concludingRuleTypes = sequent.conclusion.GetConcludingRuleTypes();
            Proof      subproof            = null;

            foreach (RuleType ruleType in concludingRuleTypes)
            {
                if (rules.ContainsKey(ruleType))
                {
                    subproof = TryRule(sequent, rules[ruleType]);
                    if (subproof != null)
                    {
                        proof.AddStepsFromProof(subproof);
                        break;
                    }
                }
            }

            truths.RemoveAll(premiseSteps);
            proofStack.Pop();

            if (currentRule == RuleType.OR_Elimination)
            {
                orEliminationPremises.Pop();
            }

            if (subproof == null)
            {
                return(null);
            }

            return(proof);
        }
Example #5
0
        public void Visit(Hypothesis hypothesis)
        {
            Sequent sequent = new Sequent(
                new ISymbol[] { hypothesis.premise },
                hypothesis.conclusion
                );

            Proof subproof = solver.Prove(sequent);

            if (subproof != null)
            {
                Result = new Proof();
                Result.AddProofStep(subproof);
            }
        }
Example #6
0
        static bool DoProof(Solver solver, int problemNumber)
        {
            Sequent sequent = problems[problemNumber];
            Proof   proof   = solver.Prove(sequent);

            if (proof == null)
            {
                Console.WriteLine("The following sequent could not be proven:");
                Console.WriteLine(sequent.ToString());
                return(false);
            }
            else
            {
                proof.PrintToConsole();
                return(true);
            }
        }
Example #7
0
        private Proof TryProve(ISymbol requiredPremise, InferenceRule rule, FormulaMapping mapping, int premiseIndex, ref RuleStep step)
        {
            ISymbol lastOEPremise = currentOEPremise;

            if (rule.type == RuleType.OR_Elimination)
            {
                currentOEPremise = rule.premises[0].ApplyMapping(mapping);
            }

            SolverVisitor solverVisitor = new SolverVisitor(this);

            requiredPremise.Accept(solverVisitor);

            if (rule.type == RuleType.OR_Elimination)
            {
                currentOEPremise = lastOEPremise;
            }

            if (solverVisitor.Result != null)
            {
                Proof proof = solverVisitor.Result;
                step.AddReferredStep(proof.ProofSteps[^ 1]);
Example #8
0
        private bool MatchPremises(InferenceRule rule, FormulaMapping mapping, ref Proof proof, ref RuleStep step, int premiseIndex = 0)
        {
            if (premiseIndex >= rule.premises.Count)
            {
                return(true);
            }

            ISymbol premise = rule.premises[premiseIndex];

            List <MappingResult> nonRootMappings = new List <MappingResult>();

            for (int i = 0; i < truths.Count; i++)
            {
                IProofStep truth = truths[i];
                foreach (MappingResult mappingResult in FindFormulaMappings(premise, truth.Conclusion, mapping))
                {
                    if (mappingResult.isRoot)
                    {
                        step.AddReferredStep(truth);

                        if (MatchPremises(rule, mappingResult.mapping, ref proof, ref step, premiseIndex + 1))
                        {
                            break;
                        }

                        step.PopReferredStep();
                    }
                    else
                    {
                        // Do non-root options later for efficiency
                        nonRootMappings.Add(mappingResult);
                    }
                }

                if (step.referredSteps.Count >= rule.premises.Count)
                {
                    return(true);
                }
            }

            foreach (MappingResult mappingResult in nonRootMappings)
            {
                Proof newProof = TryProve(mappingResult.formula, rule, mappingResult.mapping, premiseIndex, ref step);
                if (newProof != null)
                {
                    proof.AddStepsFromProof(newProof);
                    return(true);
                }

                if (step.referredSteps.Count >= rule.premises.Count)
                {
                    return(true);
                }
            }

            if (mapping.Count >= rule.maxFormulaIndex)
            {
                RuleType lastUnreferredRuleBefore = lastUnreferredRule;

                if (rule.type == RuleType.Double_Negation_Elimination && lastUnreferredRule == RuleType.Double_Negation_Elimination)
                {
                    return(false);
                }

                lastUnreferredRule = rule.type;

                ISymbol mappedPremise = premise.ApplyMapping(mapping);
                Proof   newProof      = TryProve(mappedPremise, rule, mapping, premiseIndex, ref step);
                if (newProof != null)
                {
                    proof.AddStepsFromProof(newProof);
                    return(true);
                }

                lastUnreferredRule = lastUnreferredRuleBefore;
            }

            // Proof is impossible (invalid)
            return(false);
        }