Helper ChoiceAlter

Jan Burse, created May 13. 2019
package jekpro.model.builtin;
import jekpro.model.inter.AbstractChoice;
import jekpro.model.inter.Engine;
import jekpro.model.molec.AbstractUndo;
import jekpro.model.molec.CallFrame;
import jekpro.model.molec.EngineException;
import jekpro.model.rope.Directive;
import jekpro.model.rope.Intermediate;
import jekpro.tools.term.SkelCompound;
/**
* <p>Provides a choice point for ;/2.</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 final class ChoiceAlter extends AbstractChoice {
protected Object at;
protected final Intermediate goalskel;
protected final AbstractUndo mark;
public int barrier = -2;
/**
* <p>Create an abstract choice inspect.</p>
*
* @param n The molec.
* @param r The continuation skel.
* @param u The continuation display.
* @param m The mark.
*/
ChoiceAlter(AbstractChoice n, Object a,
Intermediate r, CallFrame u,
AbstractUndo m) {
super(n, u);
goalskel = r;
mark = m;
at = a;
}
/**
* <p>Logically evaluate a term in a list of goals for an additional time.</p>
* <p>The result is returned via the contskel and contdisplay of the engine.</p>
*
* @param en The engine.
* @return True if the predicate succeeded, otherwise false.
* @throws EngineException Shit happens.
*/
public boolean moniNext(Engine en)
throws EngineException {
/* remove choice point */
en.choices = next;
en.number--;
/* undo begin condition */
if (barrier != -2) {
goaldisplay.barrier = barrier;
barrier = -2;
}
/* undo bindings */
en.contskel = goalskel;
en.contdisplay = goaldisplay;
en.fault = null;
en.releaseBind(mark);
if (en.fault != null)
throw en.fault;
if (at == null) {
return false;
} else if (Directive.isAlternative(at)) {
SkelCompound sc = (SkelCompound) at;
at = sc.args[1];
/* reuse choice point */
en.choices = this;
en.number++;
en.contskel = (Directive) sc.args[0];
return true;
} else if (Directive.isGuard(at)) {
SkelCompound sc = (SkelCompound) at;
at = null;
/* reuse choice point */
en.choices = this;
en.number++;
en.contskel = (Directive) sc.args[0];
return true;
} else {
en.contskel = (Directive) at;
return true;
}
}
/**
* <p>Free data used to logically evaluate a term an additional time.</p>
* <p>The current exception is passed via the engine fault.</p>
* <p>The new current exception is returned via the engine fault.</p>
* <p>The current contskel and contdisplay of the engine is not changed.</p>
*
* @param n The cut level.
* @param en The engine.
*/
public final void moniCut(int n, Engine en) {
/* remove choice point */
en.choices = next;
en.number--;
/* undo begin condition */
if (barrier != -2) {
goaldisplay.barrier = barrier;
barrier = -2;
}
}
}

Comments