Dear Vincent, let me first elaborate a little bit how Gecode's variables and propagators are structured before I actually attempt to give an answer.
Gecode has three important concepts regarding variables: - variables: they are used for modeling, and the only operations they provide are good for modeling. In particular, variables to not provide operations to update their domain. Examples are IntVar, BoolVar, etc. Variables are hence provide nothing but an interface to variable implementations (actually, variables are implemented as a pointer to variable implementations). - variable implementations: they are the real objects storing the domain and which propagators and advisors must be executed when the domain changes. They themselves are constructed in two steps: a domain independent stub that is automatically generated from a simple description (just a few lines). The stub is concerned with events, how propagators can be subscribed to, and linking the variable implementations to the Gecode kernel etc. The real variable implementation then inherits from the generated stub and adds the variable domain and so on. - views: like variables they are nothing but an interface for variable implementations. However, views are used by propagators and branching and provide operations to update variable domains, subscribe propagators to changes, and so on. More importantly, for the same variable implementation several views exist: a MinusView for a variable implementation x, for example, provides an interface that behaves as if the operations on the MinusView are executed on -x rather than x. Examples are IntView, BoolView, MinusView, OffsetView, ... For more on views there is paper on the Gecode webpage. Propagators themselves have two parts: a post function and the actual propagator. A post function (such as rel, distinct, linear, etc.) is used for modeling and hence takes variables as arguments. It then chooses the right propagator and the right views (converting variables to views by passing the underlying reference to the variable implementation). Propagators are typically parametric (as templates in C++) with respect to the view they are using: for example, the Max propagator is instantiated for the max posting function with an IntView whereas it is also instantiated with a MinusView for the min posting function. Sorry for the long blurb, let's move to the answer: as Gecode is designed, you can reuse propagators provided that you implement: a variable implementation by yourself (that's what you want to do), variables for them (so that you can model), and views for them (so that you can reuse the propagators), post functions (because they talk about your variables). This is a lot of effort! If you want to make something that is used (rather than an experiment), then one could also make views and variables parametric wrt the variable implementation used. That is easy but requires intimate Gecode knowledge. Then, in principal, one could also make the post functions parametric but this is almost impossible in reality as they should provide simple static linkage as they constitute the basic interface to Gecode. So it really depends on what you want to do. For an experiment, hack the variable implementation. For something, first do the experiment ;-) What do you want to do? Do you think it me be generally useful to be included in Gecode anyway? All the best Christian -- Christian Schulte, www.ict.kth.se/~cschulte/ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Vincent Barichard Sent: Wednesday, April 02, 2008 4:08 PM To: gecode list Subject: [gecode-users] Extending Integer Variable Hi, I am trying to extend IntVar in order to use it in my self(-made algorithms. I would like to use an unaltered Gecode, but I need to add an "int" member in the IntVar implementation. I don't want to make my own Integer Variable class because I also need to use the algorithms designed in Gecode. Is there a clean way to extend this class (by inheritance maybe ....) and add a member without altering Gecode ? Thank you for your assistance. Best regards, Vincent -- Vincent Barichard Université d'Angers (LERIA) Tel: 02 41 73 52 06 Département Informatique Fax: 02 41 73 50 73 H203 _______________________________________________ Gecode users mailing list [EMAIL PROTECTED] https://www.gecode.org/mailman/listinfo/gecode-users _______________________________________________ Gecode users mailing list [EMAIL PROTECTED] https://www.gecode.org/mailman/listinfo/gecode-users
