public void Visit(Atom atom)
{
Sequent sequent = new Sequent(
new ISymbol[0],
atom
);
Result = solver.Prove(sequent);
}
public void Visit(Contradiction contradiction)
{
Sequent sequent = new Sequent(
new ISymbol[0],
contradiction
);
Result = solver.Prove(sequent);
}
public void Visit(AND and)
{
Sequent sequent = new Sequent(
new ISymbol[0],
and
);
Result = solver.Prove(sequent);
}
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);
}
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);
}
}
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);
}
}
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]);
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);
}
