Helper "AbstractUndo"

Jan Burse, created Aug 17. 2019
package jekpro.model.molec;
import jekpro.model.inter.Engine;
* <p>This class provides a trailed variable binder.</p>
* <p/>
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies GmbH makes no warranties
* regarding the provided information. XLOG Technologies GmbH assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies GmbH.
* <p/>
* Rights & License
* All industrial property rights regarding the information - copyright
* and patent rights in particular - are the sole property of XLOG
* Technologies GmbH. If the company was not the originator of some
* excerpts, XLOG Technologies GmbH has at least obtained the right to
* reproduce, change and translate the information.
* <p/>
* Reproduction is restricted to the whole unaltered document. Reproduction
* of the information is only allowed for non-commercial uses. Selling,
* giving away or letting of the execution of the library is prohibited.
* The library can be distributed as part of your applications and libraries
* for execution provided this comment remains unchanged.
* <p/>
* Restrictions
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
* <p/>
* Trademarks
* Jekejeke is a registered trademark of XLOG Technologies GmbH.
public abstract class AbstractUndo {
public AbstractUndo next;
private AbstractUndo prev;
* <p>Restore state as desired and remove bind from the engine.</p>
* <p>The current exception is passed via the engine skel.</p>
* <p>The new current exception is returned via the engine skel.</p>
* @param en The engine.
public abstract void unbind(Engine en);
* <p>Remove this bind from the engine.</p>
* @param en The engine.
void removeBind(Engine en) {
AbstractUndo f = prev;
prev = null;
AbstractUndo g = next;
next = null;
if (f != null) { = g;
} else {
en.bind = g;
if (g != null)
g.prev = f;
* <p>Add this bind to the engine.</p>
* @param en The engine.
void addBind(Engine en) {
AbstractUndo f = en.bind;
if (f != null)
f.prev = this;
next = f;
en.bind = this;