public State()
{
_stack = new Stack<Step>();
_prevStep = null;
_resultStack = new Stack<object>();
_constScope = new ConstScope( null );
_lookupScope = new LookupScope( _constScope );
_rootScope = new StandardScope( _lookupScope );
_baggage = new StandardScope();
}
/// <summary>
/// Sets a callback that will be called whenever a scope can't find an object.
/// </summary>
/// <param name="lookup"></param>
public void setScopeCallback( LookupScope.LookupDelegate lookup )
{
_lookupScope.lookup = lookup;
}