/// <summary>
/// Queries a solver for a goal
/// </summary>
public static IQueryResult Query(this ISolver solver, ILiteral goal)
{
// Result is false for something without a key
if (goal.UnificationKey == null)
{
return(new BasicQueryResult(false, new EmptyBinding(null)));
}
// Compile the query
var unifier = new SimpleUnifier();
var assignments = new PredicateAssignmentList();
// Assume we have a basic predicate
foreach (var arg in goal.Dependencies)
{
assignments.AddArgument(arg);
}
// Run through the unifier
var freeVariableNames = unifier.QueryUnifier.Bind(assignments.Assignments);
var freeVariables = freeVariableNames.Select(variable => unifier.GetVariableLocation(variable).Dereference());
unifier.QueryUnifier.Compile(assignments.Assignments);
// Call via the solver
var moveNext = solver.Call(goal.UnificationKey, unifier.GetArgumentVariables(assignments.CountArguments()));
Func <IQueryResult> nextResult = () =>
{
// Update the variables to the next result
var succeeded = moveNext();
// Nothing to do if we didn't succeed
if (!succeeded)
{
return(new BasicQueryResult(false, new EmptyBinding(null)));
}
// Bind the variables
var variableValues = freeVariables
.Select(varRef => varRef.Freeze())
.Zip(freeVariableNames, (value, name) => new { Value = value, Name = name }).ToArray();
var binding = new BasicBinding(null, variableValues.ToDictionary(val => val.Name, val => val.Value));
// Return the result
return(new BasicQueryResult(true, binding));
};
// Chain to produce the final result
return(new ChainedResult(nextResult(), () => Task.FromResult(nextResult())));
}
public void FunctorUnifiesWithBindings()
{
var tA = Literal.NewFunctor(1);
var vX = Literal.NewVariable();
var vY = Literal.NewVariable();
var aX = Literal.NewAtom();
var aOfX = tA.With(vX); // a(x)
var aOfY = tA.With(vY); // a(Y)
var bindings = new BasicBinding(aX, new[] {
new { var = vX, val = aX }
}.ToDictionary(item => item.var, item => item.val));
var unified = aOfY.Unify(aOfX, bindings);
Assert.IsNotNull(unified);
Assert.AreEqual(aX, unified.GetValueForVariable(vY));
}
