/// <summary>
/// Solves a subclause
/// </summary>
private Func<bool> SolveSubclause(AssignmentData clause, SimpleUnifier unifier, Func<bool> solvePreviousClause)
{
// Create a new trail
unifier.PushTrail();
Func<bool> nextInThisClause = null;
return () =>
{
if (nextInThisClause == null || !nextInThisClause())
{
// Reset the state and get the solution for the previous clause
unifier.ResetTrail();
if (!solvePreviousClause())
{
return false;
}
// Push a new trail for this clause
unifier.PushTrail();
// Solve this clause
unifier.QueryUnifier.Bind(clause.Assignments);
if (!unifier.QueryUnifier.Compile(clause.Assignments))
{
return false;
}
// Call the predicate
nextInThisClause = _subclauseSolver.Call(clause.PredicateName, unifier.GetArgumentVariables(clause.NumArguments));
// Result depends on the next item in this clause
return nextInThisClause();
}
else
{
// nextInThisClause() returned true, so this clause was solved
return true;
}
};
}
