/// <summary>
/// On a right activation of a negative node (when a WME is added to its alpha memory),
/// we look for any tokens in its memory consistent with the WME; for each such token, we add
/// this WME to its local result memory. Also, if the number of results changes from zero to
/// one - indicating that the negated condition was previously true but is now false - then we
/// call the delete-descendents-of-token helper function to delete any tokens lower in the network
/// that depend on this token.
/// </summary>
/// <param name="node">The node.</param>
/// <param name="w">The w.</param>
private void negative_node_right_activation(NegativeNode node, WME w)
{
foreach (Token t in node.Items)
{
if (perform_join_tests(node.Tests, t, w))
{
if (t.JoinResults.Count == 0)
{
delete_descendents_of_token(t);
}
NegativeJoinResult jr = new NegativeJoinResult();
jr.Owner = t;
jr.WME = w;
t.JoinResults.AddToFront(jr);
w.NegativeJoinResults.AddToFront(jr);
}
}
}
/// <summary>
/// On a left activation
/// (when there is a new match for all the earlier conditions), we build and store a new token, perform
/// a join for the token, store the join results in the token structure, and pass the token onto any
/// successor nodes if there were no join results.
/// </summary>
/// <param name="node">The node.</param>
/// <param name="t">The t.</param>
/// <param name="w">The w.</param>
private void negative_node_left_activation(NegativeNode node, Token t, WME w)
{
// *** Right Unlinking ***
if (node.Items.Count == 0)
relink_to_alpha_memory(node);
// *** End Right Unlinking ***
Token new_token = make_token(node, t, w);
node.Items.AddToFront(new_token);
foreach (ItemInAlphaMemory item in node.AlphaMemory.Items)
{
if (perform_join_tests(node.Tests, new_token, item.WME))
{
NegativeJoinResult jr = new NegativeJoinResult();
jr.Owner = new_token;
jr.WME = w;
new_token.JoinResults.AddToFront(jr);
w.NegativeJoinResults.AddToFront(jr);
}
}
if (new_token.JoinResults.Count == 0)
{
foreach (ReteNode child in node.Children)
{
left_activation(child, new_token, null);
}
}
}