public AtomicSentence apply(TermEquality assertion,
AtomicSentence expression)
{
AtomicSentence altExpression = null;
IdentifyCandidateMatchingTerm icm = getMatchingSubstitution(assertion
.getTerm1(), expression);
if (null != icm)
{
Term replaceWith = substVisitor.subst(
icm.getMatchingSubstitution(), assertion.getTerm2());
// Want to ignore reflexivity axiom situation, i.e. x = x
if (!icm.getMatchingTerm().Equals(replaceWith))
{
ReplaceMatchingTerm rmt = new ReplaceMatchingTerm();
// Only apply demodulation at most once on each call.
altExpression = rmt.replace(expression, icm.getMatchingTerm(),
replaceWith);
}
}
return(altExpression);
}
public List <Clause> apply(Clause c1, Clause c2, bool standardizeApart)
{
List <Clause> paraExpressions = new List <Clause>();
for (int i = 0; i < 2; i++)
{
Clause topClause, equalityClause;
if (i == 0)
{
topClause = c1;
equalityClause = c2;
}
else
{
topClause = c2;
equalityClause = c1;
}
foreach (Literal possEqLit in equalityClause.getLiterals())
{
// Must be a positive term equality to be used
// for paramodulation.
if (possEqLit.isPositiveLiteral() &&
possEqLit.getAtomicSentence() is TermEquality)
{
TermEquality assertion = (TermEquality)possEqLit
.getAtomicSentence();
// Test matching for both sides of the equality
for (int x = 0; x < 2; x++)
{
Term toMatch, toReplaceWith;
if (x == 0)
{
toMatch = assertion.getTerm1();
toReplaceWith = assertion.getTerm2();
}
else
{
toMatch = assertion.getTerm2();
toReplaceWith = assertion.getTerm1();
}
foreach (Literal l1 in topClause.getLiterals())
{
IdentifyCandidateMatchingTerm icm = getMatchingSubstitution(
toMatch, l1.getAtomicSentence());
if (null != icm)
{
Term replaceWith = substVisitor.subst(icm
.getMatchingSubstitution(),
toReplaceWith);
// Want to ignore reflexivity axiom situation,
// i.e. x = x
if (icm.getMatchingTerm().Equals(replaceWith))
{
continue;
}
ReplaceMatchingTerm rmt = new ReplaceMatchingTerm();
AtomicSentence altExpression = rmt.replace(l1
.getAtomicSentence(), icm
.getMatchingTerm(), replaceWith);
// I have an alternative, create a new clause
// with the alternative and the substitution
// applied to all the literals before returning
List <Literal> newLits = new List <Literal>();
foreach (Literal l2 in topClause.getLiterals())
{
if (l1.Equals(l2))
{
newLits
.Add(l1
.newInstance((AtomicSentence)substVisitor
.subst(
icm
.getMatchingSubstitution(),
altExpression)));
}
else
{
newLits
.Add(substVisitor
.subst(
icm
.getMatchingSubstitution(),
l2));
}
}
// Assign the equality clause literals,
// excluding
// the term equality used.
foreach (Literal l2 in equalityClause.getLiterals())
{
if (possEqLit.Equals(l2))
{
continue;
}
newLits.Add(substVisitor.subst(icm
.getMatchingSubstitution(), l2));
}
// Only apply paramodulation at most once
// for each term equality.
Clause nc = null;
if (standardizeApart)
{
sApart.standardizeApart(newLits,
_emptyLiteralList, _saIndexical);
nc = new Clause(newLits);
}
else
{
nc = new Clause(newLits);
}
nc
.setProofStep(new ProofStepClauseParamodulation(
nc, topClause, equalityClause,
assertion));
if (c1.isImmutable())
{
nc.setImmutable();
}
if (!c1.isStandardizedApartCheckRequired())
{
c1.setStandardizedApartCheckNotRequired();
}
paraExpressions.Add(nc);
break;
}
}
}
}
}
}
return(paraExpressions);
}