// Note: see page 327.
public StandardizeApartResult GetStandardizeApartResult(ISentence aSentence,
IStandardizeApartIndexical standardizeApartIndexical)
{
var toRename = variableCollector.CollectAllVariables(aSentence);
IDictionary <Variable, ITerm> renameSubstitution = new Dictionary <Variable, ITerm>();
IDictionary <Variable, ITerm> reverseSubstitution = new Dictionary <Variable, ITerm>();
foreach (var var in toRename)
{
Variable v = null;
do
{
v = new Variable(standardizeApartIndexical.GetPrefix()
+ standardizeApartIndexical.GetNextIndex());
// Ensure the new variable name is not already
// accidentally used in the sentence
} while (toRename.Contains(v));
renameSubstitution[var] = v;
reverseSubstitution[v] = var;
}
var standardized = substVisitor.Subst(renameSubstitution, aSentence);
return(new StandardizeApartResult(aSentence, standardized,
renameSubstitution, reverseSubstitution));
}
// Note: You can subclass and override this method in order
// to re-implement the OCCUR-CHECK?() to always
// return false if you want that to be the default
// behavior, as is the case with Prolog.
protected bool OccurCheck(IDictionary <Variable, ITerm> theta, Variable var, IFOLNode x)
{
if (x is Function)
{
var varsToCheck = _variableCollector.CollectAllVariables((Function)x);
if (varsToCheck.Contains(var))
{
return(true);
}
// Now need to check if cascading will cause occurs to happen
// e.g.
// Loves(SF1(v2),v2)
// Loves(v3,SF0(v3))
// or
// P(v1,SF0(v1),SF0(v1))
// P(v2,SF0(v2),v2 )
// or
// P(v1, F(v2),F(v2),F(v2),v1, F(F(v1)),F(F(F(v1))),v2)
// P(F(v3),v4, v5, v6, F(F(v5)),v4, F(v3), F(F(v5)))
return(this.CascadeOccurCheck(theta, var, varsToCheck,
new HashedSet <Variable>(varsToCheck)));
}
return(false);
}