/// <summary>
/// Transforms the term.
/// </summary>
/// <param name="term">Term.</param>
/// <returns>Transformed term.</returns>
public ITerm Visit(VariableTerm term)
{
ConstantID substitutedValue;
if (Substitution.TryGetValue(term.NameId, out substitutedValue))
{
return(new ConstantTerm(substitutedValue, IdManager));
}
return(term.Clone());
}
/// <summary>
/// Extracts the parameters from the given term.
/// </summary>
/// <param name="term">Term.</param>
private void ExtractParameters(ITerm term)
{
VariableTerm variableTerm = term as VariableTerm;
if (variableTerm != null)
{
CollectedParameters.Add(variableTerm.NameId);
return;
}
ObjectFunctionTerm objectFunctionTerm = term as ObjectFunctionTerm;
if (objectFunctionTerm != null)
{
ExtractParameters(objectFunctionTerm.FunctionAtom);
}
}
/// <summary>
/// Checks whether the term needs a rename and performs the rename.
/// </summary>
/// <param name="term">Predicate or function term.</param>
private void CheckAndRenameTerm(ITerm term)
{
VariableTerm variableTerm = term as VariableTerm;
if (variableTerm != null)
{
int newParameterId;
if (ParametersRemapping.TryGetValue(variableTerm.NameId, out newParameterId))
{
variableTerm.NameId = newParameterId;
}
return;
}
ObjectFunctionTerm objectFunctionTerm = term as ObjectFunctionTerm;
if (objectFunctionTerm != null)
{
CheckAndRenameAtom(objectFunctionTerm.FunctionAtom);
}
}
/// <summary>
/// Gets the unification with the specified atom, i.e. calculates the variable substitution required to ground variable terms of the
/// current atom with the grounded terms (i.e. constants) of the other atom.
/// </summary>
/// <param name="referenceAtom">Reference atom.</param>
/// <returns>Unification in the form of variable substitution.</returns>
public ISubstitution GetUnificationWith(IAtom referenceAtom)
{
Debug.Assert(GetNameId() == referenceAtom.GetNameId() && GetTerms().Count == referenceAtom.GetTerms().Count, "Unification of incompatible atoms!");
ISubstitution unification = new Substitution();
int termIndex = 0;
foreach (var term in GetTerms())
{
VariableTerm variableTerm = term as VariableTerm;
if (variableTerm != null)
{
ConstantTerm valueTerm = referenceAtom.GetTerms()[termIndex] as ConstantTerm;
if (valueTerm != null)
{
unification.Add(variableTerm.NameId, valueTerm.NameId);
}
}
++termIndex;
}
return(unification);
}
/// <summary>
/// Visits expression term.
/// </summary>
/// <param name="term">Expression term.</param>
public void Visit(VariableTerm term)
{
TermStack.Push(Substitution.GetValue(term.NameID));
}