public IEnumerable <IDebugEvent> Solve (Compiled.Goal [] goalDefs)
{
// Instantiate the goals.
var queryArgumentInstantiator = new ArgumentInstantiator();
var goals = InstantiateGoals (goalDefs, queryArgumentInstantiator);
frame = new Frame (goals, null, new BoundVariableSet (), queryArgumentInstantiator.Variables);
// ReSharper disable ConditionIsAlwaysTrueOrFalse
while (frame != null)
// ReSharper restore ConditionIsAlwaysTrueOrFalse
{
if (frame.GoalsProven == frame.Goals.Length)
{
// No more goals to prove or it's a fact.
System.Diagnostics.Debug.Assert (frame.Goals.All (g => g.CurrentFrame != null));
if (frame.Parent == null)
{
yield return new Solution (frame);
foreach (var e in GoToLastChoicePoint ())
yield return e;
}
else
{
// go on and prove the next parent goal.
frame = frame.Parent;
frame.GoalsProven++;
}
continue;
}
var goal = frame.Goals [frame.GoalsProven];
// Check that the same goal is not on the stack to prevent infinite loops.
if (AlreadyOnTheStack (goal))
{
foreach (var e in Backtrack ())
yield return e;
}
else
{
var newFrame = goal.GetNextFrame ();
if (newFrame == null)
{
foreach (var e in Backtrack ())
yield return e;
}
else
{
yield return new Enter (newFrame);
frame = newFrame; // decend the tree
}
}
}
}
Frame Unify (Compiled.Clause clause)
{
var boundVariables = new BoundVariableSet ();
var argumentInstantiator = new ArgumentInstantiator ();
var clauseHeadArguments = clause.Head.Arguments.Select (a => a.Accept(argumentInstantiator)).ToArray();
if (boundVariables.ZipUnify (Arguments, clauseHeadArguments))
{
Goal [] goals = EngineInternals.InstantiateGoals (clause.Body, argumentInstantiator);
return new Frame (goals, this, boundVariables, argumentInstantiator.Variables);
}
return null;
}
private static Goal CreateGoal (ArgumentInstantiator visitor, Compiled.Goal goalDef)
{
var arguments = goalDef.Arguments.Select(a => a.Accept(visitor)).ToArray();
var predicate = goalDef.Predicate;
var goal = predicate.Accept (new GoalInstantiator ());
goal.Arguments = arguments;
goal.Definition = goalDef;
goal.Restart ();
return goal;
}
// ReSharper disable ParameterTypeCanBeEnumerable.Global
internal static Goal [] InstantiateGoals (Compiled.Goal [] goalDefs, ArgumentInstantiator argumentInstantiator)
// ReSharper restore ParameterTypeCanBeEnumerable.Global
{
return goalDefs.Select (goalDef => CreateGoal (argumentInstantiator, goalDef)).ToArray ();
}
