internal BacktrackingPredicate Add(Functor functor, BacktrackingPredicateDelegate backtrackingPredicateDelegate)
{
if (functor == null)
{
throw new ArgumentNullException("functor");
}
if (backtrackingPredicateDelegate == null)
{
throw new ArgumentNullException("backtrackingPredicateDelegate");
}
BacktrackingPredicate backtrackingPredicate = Methods.Add(functor, backtrackingPredicateDelegate);
return(backtrackingPredicate);
}
internal BacktrackingPredicate Add(Functor functor, BacktrackingPredicateDelegate backtrackingPredicateDelegate)
{
if (functor == null)
{
throw new ArgumentNullException("functor");
}
if (backtrackingPredicateDelegate == null)
{
throw new ArgumentNullException("backtrackingPredicateDelegate");
}
if (Contains(functor))
{
throw new ArgumentException("Item already exists.", "functor");
}
var predicate = new BacktrackingPredicate(this, functor, backtrackingPredicateDelegate);
Items.Add(predicate);
Library.Touch();
return(predicate);
}
private ExecutionResults OnLibraryCallBacktrackingPredicate(WamInstruction instruction, BacktrackingPredicate predicate)
{
WamReferenceTarget[] arguments = new WamReferenceTarget[instruction.Functor.Arity];
for (int index = 0; index < instruction.Functor.Arity; ++index)
{
arguments[index] = ArgumentRegisters[index];
}
IEnumerable<bool> enumerable;
try
{
enumerable = predicate.BacktrackingPredicateDelegate(this, arguments);
}
catch
{
// Backtrack on exception.
//
return ExecutionResults.Backtrack;
}
IEnumerator<bool> enumerator = enumerable.GetEnumerator();
ChoicePoint = new WamChoicePoint(ChoicePoint, Environment, StackIndex, ReturnInstructionPointer, ArgumentRegisters, CutChoicePoint);
ChoicePoint.BacktrackInstructionPointer = InstructionPointer.GetNext();
ChoicePoint.PredicateEnumerator = enumerator;
InstructionPointer = ChoicePoint.BacktrackInstructionPointer;
PredicateEnumerator = ChoicePoint.PredicateEnumerator;
return ExecutionResults.None;
}
ExecutionResults OnLibraryCallBacktrackingPredicate(WamInstruction instruction, BacktrackingPredicate predicate)
{
var arguments = new WamReferenceTarget[instruction.Functor.Arity];
for (var index = 0; index < instruction.Functor.Arity; ++index)
{
arguments[index] = ArgumentRegisters[index];
}
IEnumerable <bool> enumerable;
try
{
enumerable = predicate.BacktrackingPredicateDelegate(this, arguments);
}
catch
{
// Backtrack on exception.
//
return(ExecutionResults.Backtrack);
}
var enumerator = enumerable.GetEnumerator();
ChoicePoint = new WamChoicePoint(ChoicePoint, Environment, StackIndex, ReturnInstructionPointer, ArgumentRegisters, CutChoicePoint)
{
BacktrackInstructionPointer = InstructionPointer.GetNext(),
PredicateEnumerator = enumerator
};
InstructionPointer = ChoicePoint.BacktrackInstructionPointer;
PredicateEnumerator = ChoicePoint.PredicateEnumerator;
return(ExecutionResults.None);
}