Re: traits getProtection
Le 04/04/2012 15:52, Adam D. Ruppe a écrit : On Wednesday, 4 April 2012 at 07:05:59 UTC, deadalnix wrote: It should be provided as lib by std.traits . And no need for language changes. It wouldn't account for the case I actually want: checking for export. Good point. You are right, it is needed in reflection.
Re: traits getProtection
Le 04/04/2012 19:43, Jonathan M Davis a écrit : In Posix-land, _everything_ is exported. AFAK, this whole idea of marking functions as exported or not is a Windows-only thing. And honestly, it's one of my biggest complaints about programming in Windows. It's seriously annoying to have to deal with constantly exporting stuff on Windows. On Linux, it _just works_. IMHO, shared libraries is one area where Windows seriously dropped the ball in comparison to *nix. In my experience, there are _far_ fewer issues with them on Linux than Windows with its export and its nonsense of having to link against a specific version of a static library to be able to link against a dynamic one. New version of gcc implemented extensions to not export everything in posix world. IIRC, clang provide this as well. Again, this is an implementation problem and shouldn't be fixed with language design decisions. Regardless, export is a Windows-only thing and is completely unusable for any kind of optimizations in the general case. This is why extensions are made for C/C++ compilers on posix systems. Allowing private in interfaces is already getting weird, because of what interfaces are for and how they work, and doing so is already arguably special casing things. Certainly, the reasons for having private in interfaces is _completely_ different from having it in classes. private in interfaces is _only_ intended for NVI, whereas NVI is _not_ the reason for having private in classes, and in fact is fairly rare thing to do with private. I don't think that it's _possible_ to overload private in any language other than C++, and I believe that a large number of C++ programmers are completely unaware that it's possible in C++. Making private in classes work the same way as it does in interfaces would be detrimental to classes just for an idiom which many programmers _never_ use (though it _is_ a useful one) - and one which works just fine with protected. I understand your point about this being weird in interfaces. Now, granted that it is likely to be like this in interfaces, let's make things consistent. I don't believe that it's currently the plan, but I don't see any problem with just making it so that protected is used in interfaces for NVI instead of private. As I already pointed out, in C++, the derived classes can already call their versions of the NVI functions, since they're private to _them_, not the base class, even if they can't call the base class implementation (if there even is one), but interfaces don't _have_ a base class implementation, so there's nothing to protect from being called anyway. So, using protected wouldn't really change anything, and it would be completely consistent with how protected is used normally. I have to agree. The difference, as stated in TDPL, is that you cannot call the private one, only override it. Second, the same method can be declared in the base class and in an interface, and in this case, we cause compile error for nothing. Why would there be a compilation error? The base class cannot call the interface's private function, so any reference to that function would be the base class' function. You have a class C and an interface I, both define the private method foo. In MyClass : C, I, if I define foo, I get an error because foo isn't virtual in C, and if I don't, I don't implement I. All it has to do is ignore C's private function in MyClass, because it's non- virtual and _can't_ be overloaded. This is possible, but this have quite a lot of implication, on reflection for instance. What about both being defined in the same module, where private stuff are accessible.
Re: traits getProtection
On Mon, 02 Apr 2012 19:10:01 +0200, Jonathan M Davis wrote: On Monday, April 02, 2012 13:26:05 Dmitry Olshansky wrote: It's all nice and well, but I believe part of the reason of say private protection is that user is never ever able to see(!) it. Thus it user can't depend on private members being there, which is a good thing. If I read it right, the technique you present allows user code to depend on private functions being there. I argue that we shouldn't even provide a _possibility_ for external stuff to depend on private members. Same argument in limited scope goes for protected. As it stands, private has _no_ effect on symbol visibility. All it affects is symbol accessibility. For instance, if you create a private alias in a module, it affects every module that imports your module, or if you create a function which causes an overload conflict, it creates an overload conflict regardless of whether it's private or not. C++ is the same way. Access modifiers are just that, _access_ modifieres. They _only_ affect accessibility, not visibility. Access modification really makes sense for nested scopes. After all you can have access to a value of a protected type. In this case changing the visibility could lead to accidental mismatches. This behavior is taken from C++ and it makes sense. Due to the .h/.cpp separation you'll also have most of the implementation symbols invisible. That's where the C++ model doesn't really map to D if 'import everything' remains the default.
Re: traits getProtection
On Wednesday, April 04, 2012 15:49:59 deadalnix wrote: > Le 04/04/2012 10:41, Jonathan M Davis a écrit : > >> Plus, this isn't a real issue, because the final keyword exists. > > > > It's a _huge_ issue, because it means that nearly every single private > > function in a class in D will need to be marked with final in order for it > > to be non-virtual and inlinable. The default becomes inefficient, and all > > just for NVI. > > OK, let me restate this. This isn't a language design issue, this is an > implementation issue. Java and C# finalize function for ages. See below. > > >> At the end, for performance concerns, what we want is that the compiler > >> or the linker were able to finalize methods that have no override, not > >> some dirty trick that break larger more important conception principles. > > > > Because of how the compilation model works, that's impossible. No class > > can > > know all of its derived classes. Not only are classes compiled completely > > independently of their derived classes, but derived classes could be > > linked in dynamically at runtime, and those classes could have been > > written long after the base class was written and compiled. So, unless > > the programmer explicitly marks a function as final, there's no way that > > the compiler can know that that function won't be overridden. > > Unless something is marked as export, no code can be linked to it at > runtime. So the linker could finalize any function that isn't export - a > vast majority. It doesn't, I admit. But this is definitively a > implementation issue, and fixing it by language design decision is a > mistake. In Posix-land, _everything_ is exported. AFAK, this whole idea of marking functions as exported or not is a Windows-only thing. And honestly, it's one of my biggest complaints about programming in Windows. It's seriously annoying to have to deal with constantly exporting stuff on Windows. On Linux, it _just works_. IMHO, shared libraries is one area where Windows seriously dropped the ball in comparison to *nix. In my experience, there are _far_ fewer issues with them on Linux than Windows with its export and its nonsense of having to link against a specific version of a static library to be able to link against a dynamic one. Regardless, export is a Windows-only thing and is completely unusable for any kind of optimizations in the general case. > >> It is not that simple. First, it introduce an inconsistency between > >> interfaces and classes for no real reasons. The only difference between > >> classes and interfaces should be that interface cannot have member data, > >> and you can inherit from multiple interfaces. Interface have been > >> created to solve the problems that exists for multiple inheritance, and > >> that is enough to solve that problem. Everything else is, again, lack of > >> separation of concerns. > > > > private is _not_ going to become virtual in classes. I believe that Walter > > has stated that it will remain non-virtual (though I'd have to dig > > through the newsgroup for the exact quote). The only question is how to > > handle it in interfaces, and as far as I know, the intention is to make > > interfaces follow TDPL with regards to private. > > I know, but Andrei seems to disagree. I also have to dig, to find it, > but I guess we can trust each other on that. Actually, I believe that Andrei agreed with Walter in the same thread that Walter agreed not to make private virtual, but I'd have to go dig it up, and unfortunately, I always have a horrible time tracking down posts. I think that it was within the last few months though. > If I restate the question, what is the benefit of having classes and > interfaces behaving differently on this point ? TDPL make it pretty > clear how it should be handled in interfaces. Classes should work the > same way. Fixing an implementation issue isn't a valid reason. Allowing private in interfaces is already getting weird, because of what interfaces are for and how they work, and doing so is already arguably special casing things. Certainly, the reasons for having private in interfaces is _completely_ different from having it in classes. private in interfaces is _only_ intended for NVI, whereas NVI is _not_ the reason for having private in classes, and in fact is fairly rare thing to do with private. I don't think that it's _possible_ to overload private in any language other than C++, and I believe that a large number of C++ programmers are completely unaware that it's possible in C++. Making private in classes work the same way as it does in interfaces would be detrimental to classes just for an idiom which many programmers _never_ use (though it _is_ a useful one) - and one which works just fine with protected. I don't believe that it's currently the plan, but I don't see any problem with just making it so that protected is used in interfaces for NVI instead of private. As I already pointed out, in C++, t
Re: traits getProtection
On Wednesday, 4 April 2012 at 07:05:59 UTC, deadalnix wrote: It should be provided as lib by std.traits . And no need for language changes. It wouldn't account for the case I actually want: checking for export.
Re: traits getProtection
Le 04/04/2012 10:41, Jonathan M Davis a écrit : Plus, this isn't a real issue, because the final keyword exists. It's a _huge_ issue, because it means that nearly every single private function in a class in D will need to be marked with final in order for it to be non-virtual and inlinable. The default becomes inefficient, and all just for NVI. OK, let me restate this. This isn't a language design issue, this is an implementation issue. Java and C# finalize function for ages. See below. At the end, for performance concerns, what we want is that the compiler or the linker were able to finalize methods that have no override, not some dirty trick that break larger more important conception principles. Because of how the compilation model works, that's impossible. No class can know all of its derived classes. Not only are classes compiled completely independently of their derived classes, but derived classes could be linked in dynamically at runtime, and those classes could have been written long after the base class was written and compiled. So, unless the programmer explicitly marks a function as final, there's no way that the compiler can know that that function won't be overridden. Unless something is marked as export, no code can be linked to it at runtime. So the linker could finalize any function that isn't export - a vast majority. It doesn't, I admit. But this is definitively a implementation issue, and fixing it by language design decision is a mistake. It is not that simple. First, it introduce an inconsistency between interfaces and classes for no real reasons. The only difference between classes and interfaces should be that interface cannot have member data, and you can inherit from multiple interfaces. Interface have been created to solve the problems that exists for multiple inheritance, and that is enough to solve that problem. Everything else is, again, lack of separation of concerns. private is _not_ going to become virtual in classes. I believe that Walter has stated that it will remain non-virtual (though I'd have to dig through the newsgroup for the exact quote). The only question is how to handle it in interfaces, and as far as I know, the intention is to make interfaces follow TDPL with regards to private. I know, but Andrei seems to disagree. I also have to dig, to find it, but I guess we can trust each other on that. In general, I'm not convinced by the authoritative argument. Both Andrei and Walter are skilled persons, but they can be wrong, especially when they don't agree. If I restate the question, what is the benefit of having classes and interfaces behaving differently on this point ? TDPL make it pretty clear how it should be handled in interfaces. Classes should work the same way. Fixing an implementation issue isn't a valid reason. Second, the same method can be declared in the base class and in an interface, and in this case, we cause compile error for nothing. Why would there be a compilation error? The base class cannot call the interface's private function, so any reference to that function would be the base class' function. You have a class C and an interface I, both define the private method foo. In MyClass : C, I, if I define foo, I get an error because foo isn't virtual in C, and if I don't, I don't implement I.
Re: traits getProtection
On Wednesday, April 04, 2012 09:04:41 deadalnix wrote: > Le 04/04/2012 04:48, Jonathan M Davis a écrit : > > On Tuesday, April 03, 2012 08:23:49 deadalnix wrote: > >> Le 02/04/2012 22:59, Simen Kjærås a écrit : > >>> On Mon, 02 Apr 2012 20:02:20 +0200, deadalnix wrote: > > Now, there are a number of people very unhappy about this state of > > affairs and > > want private to hide symbols as well (personally, I think that the > > fact that > > it makes private aliases effectively useless is reason enough to > > seriously > > reconsider the current behavior), but I don't know if there's any > > real chance > > of convincing Walter or not. > > This would be a huge mistake. For instance, private method are > sometime meant to be overridden in subclasses, which is impossible if > symbol is inaccessible. > > NVI for instance would be impossible in such a situation. > >>> > >>> NVI is perfectly possible with protected. > >> > >> You'll loose the ability to define a function, without being able to > >> call it. > > > > Except that that doesn't even actually work as discussed in this thread: > > > > http://www.digitalmars.com/d/archives/digitalmars/D/Re_Module- > > level_accessibility_118209.html#N118329 > > > > The derived class overrode the function, so it can call it. It may not be > > able to call the base class version, but it can call its own. > > It shouldn't be able to do so. This should be reserved for protected > methods. Well, that's the way that it works in C++. And it makes sense if you think about it. The derived class' method is private to _it_, not the base class, so it can still call it, even if it can't call the base class version. > > Sure, NVI is great, but it works just as well with protected. private > > doesn't actually prevent you from calling the function in the derived > > class, and even if it did, it's _not_ worth the cost of making private > > virtual by default. And as D lets the compiler control virtuality, unlike > > C++, it doesn't make any sense to make it so that the programmer can > > specifically make a private function virtual to work with NVI. So, it > > just makes more sense to use protected to do NVI. > > Visibility and virtuality are 2 completely orthogonal concerns. Mixing > both is a bad design decision, what ever is the rational behind it. > Separation of concerns is more important. They are and they aren't. There are major issues in allowing the overriding of non-virtual functions. It's far less error-prone to simply make it so that a class' member functions are always virtual unless the compiler can determine that it can make them non-virtual (which can only happen when they're final and don't override anything). D took the same route as Java in this regard. And because it took that route, the programmer has _zero_ control over the virtuality of a function, and it's very much tied to the access level of a function. That design decision is _not_ going to be changed, so the virtuality of a function is defined by its access level. > Plus, this isn't a real issue, because the final keyword exists. It's a _huge_ issue, because it means that nearly every single private function in a class in D will need to be marked with final in order for it to be non-virtual and inlinable. The default becomes inefficient, and all just for NVI. > At the end, for performance concerns, what we want is that the compiler > or the linker were able to finalize methods that have no override, not > some dirty trick that break larger more important conception principles. Because of how the compilation model works, that's impossible. No class can know all of its derived classes. Not only are classes compiled completely independently of their derived classes, but derived classes could be linked in dynamically at runtime, and those classes could have been written long after the base class was written and compiled. So, unless the programmer explicitly marks a function as final, there's no way that the compiler can know that that function won't be overridden. > > Now, it may be different with interfaces. TDPL specifically talks about > > using private for NVI with _interfaces_, not classes. Doing that sort of > > thing with interfaces requires special treatment already, and it doesn't > > affect efficiency like making private always virtual would, so that > > should be okay. In the general case though, it's just far better to use > > protected to do NVI with classes and let private be non-virtual and > > therefore efficient by default rather than inefficient by default. > > > > - Jonathan M Davis > > It is not that simple. First, it introduce an inconsistency between > interfaces and classes for no real reasons. The only difference between > classes and interfaces should be that interface cannot have member data, > and you can inherit from multiple interfaces. Interface have been > created to solve th
Re: traits getProtection
Le 04/04/2012 03:04, Robert Jacques a écrit : On Tue, 03 Apr 2012 08:30:25 -0500, Adam D. Ruppe wrote: On Tuesday, 3 April 2012 at 13:14:00 UTC, Robert Jacques wrote: As someone who has implemented a runtime reflection library in D, it is entirely possible to detect whether a function is marked private/protected or not using __traits today. How did you do it? __traits(compiles) is the best I could find, and that breaks down if you are friends (easy to happen with mixins, even if the code is in a separate file) and is kinda fragile in general since it will swallow unrelated errors too. I did it by having all the inspection routines in a private template inside a struct in another module. That is neat. It should be provided as lib by std.traits . And no need for language changes.
Re: traits getProtection
Le 04/04/2012 04:48, Jonathan M Davis a écrit : On Tuesday, April 03, 2012 08:23:49 deadalnix wrote: Le 02/04/2012 22:59, Simen Kjærås a écrit : On Mon, 02 Apr 2012 20:02:20 +0200, deadalnix wrote: Now, there are a number of people very unhappy about this state of affairs and want private to hide symbols as well (personally, I think that the fact that it makes private aliases effectively useless is reason enough to seriously reconsider the current behavior), but I don't know if there's any real chance of convincing Walter or not. This would be a huge mistake. For instance, private method are sometime meant to be overridden in subclasses, which is impossible if symbol is inaccessible. NVI for instance would be impossible in such a situation. NVI is perfectly possible with protected. You'll loose the ability to define a function, without being able to call it. Except that that doesn't even actually work as discussed in this thread: http://www.digitalmars.com/d/archives/digitalmars/D/Re_Module- level_accessibility_118209.html#N118329 The derived class overrode the function, so it can call it. It may not be able to call the base class version, but it can call its own. It shouldn't be able to do so. This should be reserved for protected methods. Sure, NVI is great, but it works just as well with protected. private doesn't actually prevent you from calling the function in the derived class, and even if it did, it's _not_ worth the cost of making private virtual by default. And as D lets the compiler control virtuality, unlike C++, it doesn't make any sense to make it so that the programmer can specifically make a private function virtual to work with NVI. So, it just makes more sense to use protected to do NVI. Visibility and virtuality are 2 completely orthogonal concerns. Mixing both is a bad design decision, what ever is the rational behind it. Separation of concerns is more important. Plus, this isn't a real issue, because the final keyword exists. At the end, for performance concerns, what we want is that the compiler or the linker were able to finalize methods that have no override, not some dirty trick that break larger more important conception principles. Now, it may be different with interfaces. TDPL specifically talks about using private for NVI with _interfaces_, not classes. Doing that sort of thing with interfaces requires special treatment already, and it doesn't affect efficiency like making private always virtual would, so that should be okay. In the general case though, it's just far better to use protected to do NVI with classes and let private be non-virtual and therefore efficient by default rather than inefficient by default. - Jonathan M Davis It is not that simple. First, it introduce an inconsistency between interfaces and classes for no real reasons. The only difference between classes and interfaces should be that interface cannot have member data, and you can inherit from multiple interfaces. Interface have been created to solve the problems that exists for multiple inheritance, and that is enough to solve that problem. Everything else is, again, lack of separation of concerns. Second, the same method can be declared in the base class and in an interface, and in this case, we cause compile error for nothing.
Re: traits getProtection
On Tuesday, April 03, 2012 08:23:49 deadalnix wrote: > Le 02/04/2012 22:59, Simen Kjærås a écrit : > > On Mon, 02 Apr 2012 20:02:20 +0200, deadalnix wrote: > >>> Now, there are a number of people very unhappy about this state of > >>> affairs and > >>> want private to hide symbols as well (personally, I think that the > >>> fact that > >>> it makes private aliases effectively useless is reason enough to > >>> seriously > >>> reconsider the current behavior), but I don't know if there's any > >>> real chance > >>> of convincing Walter or not. > >> > >> This would be a huge mistake. For instance, private method are > >> sometime meant to be overridden in subclasses, which is impossible if > >> symbol is inaccessible. > >> > >> NVI for instance would be impossible in such a situation. > > > > NVI is perfectly possible with protected. > > You'll loose the ability to define a function, without being able to > call it. Except that that doesn't even actually work as discussed in this thread: http://www.digitalmars.com/d/archives/digitalmars/D/Re_Module- level_accessibility_118209.html#N118329 The derived class overrode the function, so it can call it. It may not be able to call the base class version, but it can call its own. Sure, NVI is great, but it works just as well with protected. private doesn't actually prevent you from calling the function in the derived class, and even if it did, it's _not_ worth the cost of making private virtual by default. And as D lets the compiler control virtuality, unlike C++, it doesn't make any sense to make it so that the programmer can specifically make a private function virtual to work with NVI. So, it just makes more sense to use protected to do NVI. Now, it may be different with interfaces. TDPL specifically talks about using private for NVI with _interfaces_, not classes. Doing that sort of thing with interfaces requires special treatment already, and it doesn't affect efficiency like making private always virtual would, so that should be okay. In the general case though, it's just far better to use protected to do NVI with classes and let private be non-virtual and therefore efficient by default rather than inefficient by default. - Jonathan M Davis
Re: traits getProtection
On Tue, 03 Apr 2012 08:30:25 -0500, Adam D. Ruppe wrote: On Tuesday, 3 April 2012 at 13:14:00 UTC, Robert Jacques wrote: As someone who has implemented a runtime reflection library in D, it is entirely possible to detect whether a function is marked private/protected or not using __traits today. How did you do it? __traits(compiles) is the best I could find, and that breaks down if you are friends (easy to happen with mixins, even if the code is in a separate file) and is kinda fragile in general since it will swallow unrelated errors too. I did it by having all the inspection routines in a private template inside a struct in another module.
Re: traits getProtection
On 4/3/12, Adam D. Ruppe wrote: > is kinda fragile in general since it will swallow unrelated > errors too. That's an issue I've noticed recently. msgpack-d allows me to define a custom serialization routine in my structs/classes, but it has to be a template. Then msgpack tries to instantiate it via __traits(compiles), and if it doesn't work it just skips calling the routine alltogether. So if I have invalid code in my template I'll never know because the external library just swallows the errors. It took me a long time to figure out why my routine wasn't called. I really wish DMD would semantically check templates at least partially even if they're never instantiated.
Re: traits getProtection
On Tuesday, 3 April 2012 at 13:14:00 UTC, Robert Jacques wrote: As someone who has implemented a runtime reflection library in D, it is entirely possible to detect whether a function is marked private/protected or not using __traits today. How did you do it? __traits(compiles) is the best I could find, and that breaks down if you are friends (easy to happen with mixins, even if the code is in a separate file) and is kinda fragile in general since it will swallow unrelated errors too.
Re: traits getProtection
On Mon, 02 Apr 2012 08:05:09 -0500, Dmitry Olshansky wrote: On 02.04.2012 16:04, Adam D. Ruppe wrote: On Monday, 2 April 2012 at 09:26:07 UTC, Dmitry Olshansky wrote: It's all nice and well, but I believe part of the reason of say private protection is that user is never ever able to see(!) it. Thus it user can't depend on private members being there, which is a good thing. That's not the way it is right now in D: if you use the reflection traits, you can see and access private members. Worse yet, the way it is now, there's no way to tell they are marked private when using reflection! Awful. As someone who has implemented a runtime reflection library in D, it is entirely possible to detect whether a function is marked private/protected or not using __traits today. In fact, IIRC, there is no way to break protection using __traits; what the op is referring to is .tupleof, which can be used to break protections of fields if you have the full source code.
Re: traits getProtection
On 04/03/2012 08:27 AM, deadalnix wrote: Le 03/04/2012 00:00, Timon Gehr a écrit : Making private symbols invisible to other modules or at least excluding them from symbol clashes is necessary. The current behaviour is not useful or desirable in any way. This smells like religious coding to me. Nope. NVI is perfectly possible with protected. Exactly. Furthermore, private implies final anyway. Which is complete bullshit. It is a questionable design decision. It might be reasonable to allow overriding private members, but that would mess with the vtable layout. Even in a module you may want to override a method. ... which is excluded from the public interface. There are better ways to hide a method than to mark it private in an implementation class.
Re: traits getProtection
Le 03/04/2012 00:00, Timon Gehr a écrit : Making private symbols invisible to other modules or at least excluding them from symbol clashes is necessary. The current behaviour is not useful or desirable in any way. This smells like religious coding to me. NVI is perfectly possible with protected. Exactly. Furthermore, private implies final anyway. Which is complete bullshit. Even in a module you may want to override a method.
Re: traits getProtection
Le 02/04/2012 22:59, Simen Kjærås a écrit : On Mon, 02 Apr 2012 20:02:20 +0200, deadalnix wrote: Now, there are a number of people very unhappy about this state of affairs and want private to hide symbols as well (personally, I think that the fact that it makes private aliases effectively useless is reason enough to seriously reconsider the current behavior), but I don't know if there's any real chance of convincing Walter or not. This would be a huge mistake. For instance, private method are sometime meant to be overridden in subclasses, which is impossible if symbol is inaccessible. NVI for instance would be impossible in such a situation. NVI is perfectly possible with protected. You'll loose the ability to define a function, without being able to call it. It is something you want if function have to be called by pair for example (using protected here would introduce temporal coupling). It make even more sense if you consider combining it with contract programing.
Re: traits getProtection
On 04/02/2012 10:59 PM, Simen Kjærås wrote: On Mon, 02 Apr 2012 20:02:20 +0200, deadalnix wrote: Now, there are a number of people very unhappy about this state of affairs and want private to hide symbols as well (personally, I think that the fact that it makes private aliases effectively useless is reason enough to seriously reconsider the current behavior), but I don't know if there's any real chance of convincing Walter or not. This would be a huge mistake. For instance, private method are sometime meant to be overridden in subclasses, which is impossible if symbol is inaccessible. NVI for instance would be impossible in such a situation. Making private symbols invisible to other modules or at least excluding them from symbol clashes is necessary. The current behaviour is not useful or desirable in any way. NVI is perfectly possible with protected. Exactly. Furthermore, private implies final anyway.
Re: traits getProtection
On Mon, 02 Apr 2012 20:02:20 +0200, deadalnix wrote: Now, there are a number of people very unhappy about this state of affairs and want private to hide symbols as well (personally, I think that the fact that it makes private aliases effectively useless is reason enough to seriously reconsider the current behavior), but I don't know if there's any real chance of convincing Walter or not. This would be a huge mistake. For instance, private method are sometime meant to be overridden in subclasses, which is impossible if symbol is inaccessible. NVI for instance would be impossible in such a situation. NVI is perfectly possible with protected.
Re: traits getProtection
On 1 April 2012 21:27, Adam D. Ruppe wrote:
> I've prepared a dmd pull request to add a new __trait:
> getProtection.
>
> It is meant to be used along with getMember() to add to
> the reflection capabilities, letting us use the existing
> protection qualifiers as strings.
>
> From the test:
> ==
> class Test {
>public int a;
>private int b;
>export string c;
>protected int d;
>package void e() {}
> }
>
> void main() {
>Test t;
>static assert(__traits(getProtection, __traits(getMember, t, "a")) ==
> "public");
>static assert(__traits(getProtection, __traits(getMember, t, "b")) ==
> "private");
>static assert(__traits(getProtection, __traits(getMember, t, "c")) ==
> "export");
>static assert(__traits(getProtection, __traits(getMember, t, "d")) ==
> "protected");
>static assert(__traits(getProtection, __traits(getMember, t, "e")) ==
> "package");
> }
> ==
>
>
>
> This will help D automatically generate things like
> external interfaces that use the protections.
>
> For instance, I plan to use it in my web.d to only
> make functions marked "export" available via the
> web interface. Currently, you have to use a naming
> convention to hide functions - a leading underscore -
> even on private members. This is ok, but not great.
>
> But with the protection trait, we can mark it with
> a much more natural "private", or any of the other
> specifiers D has.
>
>
> I'm sure other uses will come up too.
>
Wow, it so happens I need to use this immediately (tomorrow), and I assumed
it was already possible...
I wonder about the protection flags used this way though.
I want to generate external interfaces for all public stuff, but it
occurred to me that an explicit modifier like export would be more
appropriate to control what is exposed.
The problem with 'export' is it's already defined to export from a shared
object/dll, and my code IS a dll, so export is not something I can overload
for this purpose...
export(dll) maybe? Then you could describe other export types... ?
... this is another perfect use for... custom attributes! ;)
I also need to tag functions/classes/methods/properties as being saved,
state recorded, editor exposed, script bound... I have a bucket load of
needs for custom attributes.
Re: traits getProtection
On Monday, April 02, 2012 20:02:20 deadalnix wrote: > Le 02/04/2012 19:10, Jonathan M Davis a écrit : > > On Monday, April 02, 2012 13:26:05 Dmitry Olshansky wrote: > >> It's all nice and well, but I believe part of the reason of say private > >> protection is that user is never ever able to see(!) it. Thus it user > >> can't depend on private members being there, which is a good thing. > >> If I read it right, the technique you present allows user code to depend > >> on private functions being there. > >> I argue that we shouldn't even provide a _possibility_ for external > >> stuff to depend on private members. > >> Same argument in limited scope goes for protected. > > > > As it stands, private has _no_ effect on symbol visibility. All it affects > > is symbol accessibility. For instance, if you create a private alias in a > > module, it affects every module that imports your module, or if you > > create a function which causes an overload conflict, it creates an > > overload conflict regardless of whether it's private or not. C++ is the > > same way. Access modifiers are just that, _access_ modifieres. They > > _only_ affect accessibility, not visibility. > Reflection should reflect what the reflectee is. Private stuff are part > of the reflectee. It may be that private stuff needs to be visible for some reflection stuff (particularly if you're dealing with lower level stuff) - I don't know. But at minimum, removing it from overload resolution would be a huge win. > > Now, there are a number of people very unhappy about this state of affairs > > and want private to hide symbols as well (personally, I think that the > > fact that it makes private aliases effectively useless is reason enough > > to seriously reconsider the current behavior), but I don't know if > > there's any real chance of convincing Walter or not. > > This would be a huge mistake. For instance, private method are sometime > meant to be overridden in subclasses, which is impossible if symbol is > inaccessible. > > NVI for instance would be impossible in such a situation. 1. NVI works perfectly well with protected functions. 2. private is currently never virtual in D anyway. If you want a function to be virtual, it must be public or protected. 3. Making private virtual would be a huge detriment to the language, because it would make all classes inefficient by default. You'd have to mark all non-NVI private functions functions final for them to be non-virtual and inlinable, so the default is then inefficient just to enable NVI with private functions. And since NVI works with protected, there's no real gain. http://d.puremagic.com/issues/show_bug.cgi?id=4542 - Jonathan M Davis
Re: traits getProtection
Le 02/04/2012 19:10, Jonathan M Davis a écrit : On Monday, April 02, 2012 13:26:05 Dmitry Olshansky wrote: It's all nice and well, but I believe part of the reason of say private protection is that user is never ever able to see(!) it. Thus it user can't depend on private members being there, which is a good thing. If I read it right, the technique you present allows user code to depend on private functions being there. I argue that we shouldn't even provide a _possibility_ for external stuff to depend on private members. Same argument in limited scope goes for protected. As it stands, private has _no_ effect on symbol visibility. All it affects is symbol accessibility. For instance, if you create a private alias in a module, it affects every module that imports your module, or if you create a function which causes an overload conflict, it creates an overload conflict regardless of whether it's private or not. C++ is the same way. Access modifiers are just that, _access_ modifieres. They _only_ affect accessibility, not visibility. Reflection should reflect what the reflectee is. Private stuff are part of the reflectee. Now, there are a number of people very unhappy about this state of affairs and want private to hide symbols as well (personally, I think that the fact that it makes private aliases effectively useless is reason enough to seriously reconsider the current behavior), but I don't know if there's any real chance of convincing Walter or not. This would be a huge mistake. For instance, private method are sometime meant to be overridden in subclasses, which is impossible if symbol is inaccessible. NVI for instance would be impossible in such a situation.
Re: traits getProtection
On Monday, April 02, 2012 13:26:05 Dmitry Olshansky wrote: > It's all nice and well, but I believe part of the reason of say private > protection is that user is never ever able to see(!) it. Thus it user > can't depend on private members being there, which is a good thing. > If I read it right, the technique you present allows user code to depend > on private functions being there. > I argue that we shouldn't even provide a _possibility_ for external > stuff to depend on private members. > Same argument in limited scope goes for protected. As it stands, private has _no_ effect on symbol visibility. All it affects is symbol accessibility. For instance, if you create a private alias in a module, it affects every module that imports your module, or if you create a function which causes an overload conflict, it creates an overload conflict regardless of whether it's private or not. C++ is the same way. Access modifiers are just that, _access_ modifieres. They _only_ affect accessibility, not visibility. Now, there are a number of people very unhappy about this state of affairs and want private to hide symbols as well (personally, I think that the fact that it makes private aliases effectively useless is reason enough to seriously reconsider the current behavior), but I don't know if there's any real chance of convincing Walter or not. - Jonathan M Davis
Re: traits getProtection
On 02.04.2012 16:04, Adam D. Ruppe wrote: On Monday, 2 April 2012 at 09:26:07 UTC, Dmitry Olshansky wrote: It's all nice and well, but I believe part of the reason of say private protection is that user is never ever able to see(!) it. Thus it user can't depend on private members being there, which is a good thing. That's not the way it is right now in D: if you use the reflection traits, you can see and access private members. Worse yet, the way it is now, there's no way to tell they are marked private when using reflection! Awful. That's one of the reasons why I want to add this - it lets us check. I remember asking if private members should be hidden from reflection before, and the answer was no - I think it had to do with them being useful for serialization and stuff like that. Now I get it, traits hasIndirections would need it too, and it's too big a feat to lose it. -- Dmitry Olshansky
Re: traits getProtection
On Monday, 2 April 2012 at 09:26:07 UTC, Dmitry Olshansky wrote: It's all nice and well, but I believe part of the reason of say private protection is that user is never ever able to see(!) it. Thus it user can't depend on private members being there, which is a good thing. That's not the way it is right now in D: if you use the reflection traits, you can see and access private members. Worse yet, the way it is now, there's no way to tell they are marked private when using reflection! That's one of the reasons why I want to add this - it lets us check. I remember asking if private members should be hidden from reflection before, and the answer was no - I think it had to do with them being useful for serialization and stuff like that.
Re: traits getProtection
On 01.04.2012 22:27, Adam D. Ruppe wrote:
I've prepared a dmd pull request to add a new __trait:
getProtection.
It is meant to be used along with getMember() to add to
the reflection capabilities, letting us use the existing
protection qualifiers as strings.
From the test:
==
class Test {
public int a;
private int b;
export string c;
protected int d;
package void e() {}
}
void main() {
Test t;
static assert(__traits(getProtection, __traits(getMember, t, "a")) ==
"public");
static assert(__traits(getProtection, __traits(getMember, t, "b")) ==
"private");
static assert(__traits(getProtection, __traits(getMember, t, "c")) ==
"export");
static assert(__traits(getProtection, __traits(getMember, t, "d")) ==
"protected");
static assert(__traits(getProtection, __traits(getMember, t, "e")) ==
"package");
}
==
This will help D automatically generate things like
external interfaces that use the protections.
For instance, I plan to use it in my web.d to only
make functions marked "export" available via the
web interface. Currently, you have to use a naming
convention to hide functions - a leading underscore -
even on private members. This is ok, but not great.
But with the protection trait, we can mark it with
a much more natural "private", or any of the other
specifiers D has.
I'm sure other uses will come up too.
It's all nice and well, but I believe part of the reason of say private
protection is that user is never ever able to see(!) it. Thus it user
can't depend on private members being there, which is a good thing.
If I read it right, the technique you present allows user code to depend
on private functions being there.
I argue that we shouldn't even provide a _possibility_ for external
stuff to depend on private members.
Same argument in limited scope goes for protected.
As for export, I thinks it looks OK.
--
Dmitry Olshansky
Re: traits getProtection
On 2 April 2012 06:27, Adam D. Ruppe wrote:
> I've prepared a dmd pull request to add a new __trait:
> getProtection.
>
> It is meant to be used along with getMember() to add to
> the reflection capabilities, letting us use the existing
> protection qualifiers as strings.
>
> From the test:
> ==
> class Test {
> public int a;
> private int b;
> export string c;
> protected int d;
> package void e() {}
> }
>
> void main() {
> Test t;
> static assert(__traits(getProtection, __traits(getMember, t, "a")) ==
> "public");
> static assert(__traits(getProtection, __traits(getMember, t, "b")) ==
> "private");
> static assert(__traits(getProtection, __traits(getMember, t, "c")) ==
> "export");
> static assert(__traits(getProtection, __traits(getMember, t, "d")) ==
> "protected");
> static assert(__traits(getProtection, __traits(getMember, t, "e")) ==
> "package");
> }
> ==
>
>
>
> This will help D automatically generate things like
> external interfaces that use the protections.
>
> For instance, I plan to use it in my web.d to only
> make functions marked "export" available via the
> web interface. Currently, you have to use a naming
> convention to hide functions - a leading underscore -
> even on private members. This is ok, but not great.
>
> But with the protection trait, we can mark it with
> a much more natural "private", or any of the other
> specifiers D has.
>
>
> I'm sure other uses will come up too.
Looks good, adds a lot to the compile-time reflection capabilities. My
thoughts for it are similar to yours, generating bindings from
"export"ed members, so you don't need to maintain separate lists or
use a naming convention.
--
James Miller
Re: traits getProtection
Code: https://github.com/D-Programming-Language/dmd/pull/856
traits getProtection
I've prepared a dmd pull request to add a new __trait:
getProtection.
It is meant to be used along with getMember() to add to
the reflection capabilities, letting us use the existing
protection qualifiers as strings.
From the test:
==
class Test {
public int a;
private int b;
export string c;
protected int d;
package void e() {}
}
void main() {
Test t;
static assert(__traits(getProtection, __traits(getMember, t,
"a")) == "public");
static assert(__traits(getProtection, __traits(getMember, t,
"b")) == "private");
static assert(__traits(getProtection, __traits(getMember, t,
"c")) == "export");
static assert(__traits(getProtection, __traits(getMember, t,
"d")) == "protected");
static assert(__traits(getProtection, __traits(getMember, t,
"e")) == "package");
}
==
This will help D automatically generate things like
external interfaces that use the protections.
For instance, I plan to use it in my web.d to only
make functions marked "export" available via the
web interface. Currently, you have to use a naming
convention to hide functions - a leading underscore -
even on private members. This is ok, but not great.
But with the protection trait, we can mark it with
a much more natural "private", or any of the other
specifiers D has.
I'm sure other uses will come up too.
