public ByteCodeUnifier(ByteCodeProgram program)
{
if (program == null)
{
throw new ArgumentNullException("program");
}
_program = program;
}
/// <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);
}
}