public SimpleSingleClauseSolver(IClause clause, ISolver subclauseSolver)
{
if (clause == null)
{
throw new ArgumentNullException("clause");
}
if (subclauseSolver == null)
{
throw new ArgumentNullException("subclauseSolver");
}
_clause = clause;
_subclauseSolver = subclauseSolver;
// Compile each part of the clause to its subclauses
_clauseAssignments = new[] { clause.Implies }.Concat(clause.If)
.Select(predicate =>
{
var assignments = PredicateAssignmentList.FromPredicate(predicate);
return(new AssignmentData
{
PredicateName = predicate.UnificationKey,
NumArguments = assignments.CountArguments(),
Assignments = assignments.Assignments.ToArray()
});
})
.ToList();
}
/// <summary>
/// Retrieves an object representing the assignments for a particular literal when used as a predicate
/// </summary>
public static PredicateAssignmentList FromPredicate(ILiteral predicate)
{
var result = new PredicateAssignmentList();
if (predicate.UnificationKey != null)
{
foreach (var argument in predicate.Dependencies)
{
result.AddArgument(argument);
}
}
return(result);
}
/// <summary>
/// Retrieves an object representing the assignments for a particular literal when used as a predicate
/// </summary>
public static PredicateAssignmentList FromPredicate(ILiteral predicate)
{
var result = new PredicateAssignmentList();
if (predicate.UnificationKey != null)
{
foreach (var argument in predicate.Dependencies)
{
result.AddArgument(argument);
}
}
return result;
}
/// <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()));
}
/// <summary>
/// Compiles a clause to a bytecode program
/// </summary>
public static void Compile(this IClause clause, ByteCodeProgram program)
{
var unifier = new ByteCodeUnifier(program);
// Take each part of the clause and retrieve the assignments for it, with the 'implies' set at the start
var allPredicates = new[] { clause.Implies }.Concat(clause.If).ToArray();
var assignmentList = allPredicates
.Select(predicate => new
{
Assignments = PredicateAssignmentList.FromPredicate(predicate),
UnificationKey = predicate.UnificationKey
})
.ToArray();
// Allocate space for the arguments and any permanent variables
var permanentVariables = PermanentVariableAssignments.PermanentVariables(assignmentList.Select(assign => assign.Assignments));
var numArguments = assignmentList[0].Assignments.CountArguments();
if (permanentVariables.Count > 0 || allPredicates.Length > 1)
{
program.Write(Operation.Allocate, permanentVariables.Count, numArguments);
}
// Unify with the predicate first
unifier.ProgramUnifier.Bind(assignmentList[0].Assignments.Assignments, permanentVariables);
unifier.ProgramUnifier.Compile(assignmentList[0].Assignments.Assignments);
// Call the clauses
foreach (var assignment in assignmentList.Skip(1))
{
unifier.QueryUnifier.Bind(assignment.Assignments.Assignments, permanentVariables);
unifier.QueryUnifier.Compile(assignment.Assignments.Assignments);
program.Write(Operation.Call, assignment.UnificationKey, assignment.UnificationKey.Dependencies.Count());
}
// Deallocate any permanent variables that we might have found
if (permanentVariables.Count > 0 || allPredicates.Length > 1)
{
program.Write(Operation.Deallocate);
}
}
