private mixin function

[Regan Heath]

On Wed, 12 Apr 2006 11:44:56 -0500, Chris Nicholson-Sauls  
<ibisbasenji at gmail.com> wrote:
> Regan Heath wrote:
>> On Tue, 11 Apr 2006 16:03:36 -0400, Jarrett Billingsley   
>> <kb3ctd2 at yahoo.com> wrote:
>>
>>> "Frank Benoit" <benoit__ at __tionex.de> wrote in message
>>> news:e1gh7m$2btt$1 at digitaldaemon.com...
>>>
>>>> Never mind. Calling it with
>>>> m1.func();
>>>> works.
>>>
>>>
>>> Hahaha, it's two bugs canceling each other out (maybe).
>>   I have a feeling it's related. I think mixins have some problems  
>> which  should be addressed, or at the very least cleared up in the  
>> docs. Let me  elaborate... :)
>>  In this case a 'MixinIdentifier' has been given 'm1':
>>  mixin m!(byte) m1;
>>  The docs say: "If a mixin has a MixinIdentifier, it can be used to   
>> disambiguate" which, isn't exactly what we're using it for, but it  
>> does  seem to solve the problem. Then again, maybe this is the same bug  
>> as you  mention where a private member in another module can be  
>> accessed with it's  full name.
>>  I think part of the problem is that "A mixin has its own scope ...",  
>> this  was taken a little out of context, see:
>>   http://www.digitalmars.com/d/mixin.html
>>  It suggests to me that mixin has a scope (especially when you give it  
>> an  identifier like 'm1'). If it has a scope, and that scope is m1,  
>> then it  makes sense that need to call the function with m1.func();
>>  That said, earlier in the docs it says "The declarations in a mixin  
>> are  'imported' into the surrounding scope" and "It is analogous to  
>> cutting and  pasting the body of the template into the location of the  
>> mixin", if those  statements were true then this code should work:
>>  template m(T){
>>     private void func() {}
>> }
>>  class C{
>>     mixin m!(byte);
>>         public this(){
>>         func(); // error: func is private
>>     }
>> }
>>  (note, no identifier) but it doesn't. It gives the same error as you  
>> had  before. As there is no mixin identifier there is no solution here.
>>  I've had this exact problem with them in the past, trying to mix  
>> private  declarations into a class just plain doesn't work. Instead it  
>> results in  something akin to a derived class, where the base had  
>> private members.  They're just plain inaccessable, as you've found.
>>  I would love to see this cleaned up.
>>  Regan
>
> This might seem crazy, but bear with me.  It looks to me like the  
> function is declared as private In-Terms-Of the mixin, rather than the  
> instantiating class

Yes, that's exactly what I was suggesting by saying the result was akin to  
a derived class, eg:

class A { //AKA the mixin
   private void func() {}
}

(in a different module)
class B : A {
   this() {
     func(); //error, private
   }
}

> , therefore maybe the solution would be to be able to do this:
>
> # template m (T) {
> #   void func () {}
> # }
> #
> # class C {
> #   private mixin m!(byte);
> #
> #   public this () {
> #     func();
> #   }
> # }
>
> Note that the 'private' attribute is moved out of the template, and  
> instead applied to the mixin statement itself.  I suppose the meaning  
> ought to be something similar to the meaning of public/protected/private  
> in inheritance (iow, similar to the way "class Foo : private Bar" would  
> behave).

Only it doesn't let you go:

template m(T) {
   private void func();
   public void foo();
}

class B {
   mixin m!(byte);
}

and have 'func' private in B, and 'foo' public in B. Instead you have to  
make several templates and mix them all seperately.

Regan