Just to follow up slightly on Lydia's mail, I wanted to note: * nested classes haven't been a significant feature area for us to work on over the project's history due to the sense that we have bigger fish to fry -- both in general (e.g., parallelism, distributed memory support, performance), and in terms of the OOP features (e.g., fixing our constructor story).
* we'd be very interested in input from users on the importance of nested classes or "better" ways to do them in Chapel if you think we're headed into a bad place. * generally, when we say "similar to classes in Java", this should be interpreted in a very general sense (e.g., "as opposed to classes in C++") rather than a statement that our goal is to support the same feature set as Java and/or in the same way. -Brad On Mon, 29 Aug 2016, Lydia Duncan wrote: > Hi Jake, > > I don't think it is possible to create an instance of the inner class type > from outside of the outer class. I believe we don't allow those symbols to > be referenced outside of the scope of the outer class - this is similar to > how we treat nested functions. However, you can get an instance of the inner > class to live outside of the outer class by having the outer class return an > instance and storing that result, and you can call methods on the inner > class. > > Unfortunately a quick check through our most likely test directory didn't > reveal an exact candidate matching this scenario. The closest I could find > is this future (read: test that doesn't quite work today) example, > https://github.com/chapel-lang/chapel/blob/master/test/classes/vass/nested-class-with-user-defined-constructor-1.chpl > > A simple modification to this program will cause it to behave "properly" or > close to your purpose - merely add an "outer" arg to the inner constructor, > or remove the user-defined inner constructor entirely. > > That program stores an instance of the inner class, but it uses a method on > the outer class to generate it, so that the inner class always knows what > outer instance it points to. Note that if you try to declare the type of > "i", you get a type resolution failure. > > Hope that helps, > Lydia Duncan > > On 08/28/2016 10:09 AM, Caswell, Jacob wrote: >> >> My apologies, I found the answer to the access question in the language >> specification. However, I couldn't find an example for creating an instance >> of an inner class outside of the outside class. Is it called just as: >> >> >> class outside { >> >> ... >> >> class inside { >> >> ... >> >> } >> >> } >> >> >> var out_class : outside; >> >> var in_class : outside.inside; >> >> >> Or is there another form of declaration and initialization? >> >> >> Thank you very much, >> >> Jake >> >> >> >> ------------------------------------------------------------------------ >> *From:* Caswell, Jacob <[email protected]> >> *Sent:* Sunday, August 28, 2016 10:36 AM >> *To:* [email protected] >> *Subject:* [EXTERNAL] Nested classes in Chapel >> >> Hello all, >> >> >> I found the following tutorial that says classes in Chapel are similar to >> classes in Java. Does this mean that Chapel supports nested classes as >> well? I've been reworking some of my code to use object oriented structures >> to help facilitate task parallelism in a multilocale execution. The idea >> being that I could create an instance of the task, which needs both fields >> and methods specific to the executing locale, in a reusable way. However, >> I've been having some issues with using nested classes in my code. >> >> >> In Chapel, is it possible to create an instance of an inner class, either >> within a method from the outer class or outside of both of the classes? And >> if so, what access will the inner class have? Can it return variables from >> its outer class? Is there documentation for this functionality that I >> missed? >> >> >> Thank you very much, >> >> Jake >> >> >> >> >> ------------------------------------------------------------------------------ >> >> >> _______________________________________________ >> Chapel-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/chapel-users > > ------------------------------------------------------------------------------ _______________________________________________ Chapel-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/chapel-users
