On the Future Directions page on the D website, three features are presented.  One of which is "Mixins", something that I have never heard of before.  Would someone care to explain what this is?

Thanks,

Craig

"Craig Black" <cblack@ara.com> wrote in message news:c4a46g$jg9$1@digitaldaemon.com...
> On the Future Directions page on the D website, three features are presented.  One of which is "Mixins", something that I have never heard of before.  Would someone care to explain what this is?
>
> Thanks,
>
> Craig
>
>

A mixin is the result of mixing two or more classes together. In C++, for example, 'fstream' is a mixin of 'ifstream' and 'ofstream'. Mixins can be done by multiple inheritance or by aggregation.

On Mon, 29 Mar 2004 15:24:31 -0600 (30/Mar/04 07:24:31 AM)
, Craig Black <cblack@ara.com> wrote:

> On the Future Directions page on the D website, three features are
> presented.  One of which is "Mixins", something that I have never heard of
> before.  Would someone care to explain what this is?
>
> Thanks,
>
> Craig
>

I understand it to mean the process of creating a new class by picking out attributes and methods from two or more other classes. A bit like multiple inheritence but instead of getting everything, you get to pick which parts you want to inherit.

I could be wrong though.

-- 
Derek

Here are some references.  We have a lot of the concept, but there seem to be some things missing.  Maybe someone else can fill that in better than I...

In approximate order of increasing scope and generality:

http://www.cs.utexas.edu/users/richcar/JLMixins.html http://c2.com/cgi/wiki?MixIn http://cpptips.hyperformix.com/cpptips/mixins http://www-106.ibm.com/developerworks/java/library/j-diag1203/ http://www.rubycentral.com/book/tut_modules.html http://www.cs.utexas.edu/users/richcar/fidget.pdf http://www.iam.unibe.ch/~scg/Teaching/IOOM/PPT/VariationOnInheritance.pdf


In article <opr5ndv0f4u2m3b2@news.digitalmars.com>, Derek Parnell says...
>
>On Mon, 29 Mar 2004 15:24:31 -0600 (30/Mar/04 07:24:31 AM)
>, Craig Black <cblack@ara.com> wrote:
>
>> On the Future Directions page on the D website, three features are
>> presented.  One of which is "Mixins", something that I have never heard
>> of
>> before.  Would someone care to explain what this is?
>>
>> Thanks,
>>
>> Craig
>>
>
>I understand it to mean the process of creating a new class by picking out attributes and methods from two or more other classes. A bit like multiple inheritence but instead of getting everything, you get to pick which parts you want to inherit.
>
>I could be wrong though.
>
>-- 
>Derek

To me it seems a lot like the Objective-C concept of categories.  In ObjC, it
goes like this:  I can define
a category of any existing class, which can add methods to any pre-existing
class.  From then on, any
code that imports my category sees my methods on the class as indistinguishable
from those defined
within the class itself.

Example:

There's a class called NSData for holding binary data.  I want it to be able to
use it for GZIP
compression, so I write a category that adds zip() and unzip() methods to it,
and place it in
NSData+Gzip.h.  Then any code that has a "#include NSData+Gzip.h" will see the
zip() and unzip()
methods as if they were part of the class itself.

Ok, that was somewhat random, but it's another approach to the same basic
problem, and perhaps an
interesting idea for D.

Owen

In article <c4ags8$19tu$1@digitaldaemon.com>, larry cowan says...
>
>Here are some references.  We have a lot of the concept, but there seem to be some things missing.  Maybe someone else can fill that in better than I...
>
>In approximate order of increasing scope and generality:
>
>http://www.cs.utexas.edu/users/richcar/JLMixins.html http://c2.com/cgi/wiki?MixIn http://cpptips.hyperformix.com/cpptips/mixins http://www-106.ibm.com/developerworks/java/library/j-diag1203/ http://www.rubycentral.com/book/tut_modules.html http://www.cs.utexas.edu/users/richcar/fidget.pdf http://www.iam.unibe.ch/~scg/Teaching/IOOM/PPT/VariationOnInheritance.pdf
>
>
>In article <opr5ndv0f4u2m3b2@news.digitalmars.com>, Derek Parnell says...
>>
>>On Mon, 29 Mar 2004 15:24:31 -0600 (30/Mar/04 07:24:31 AM)
>>, Craig Black <cblack@ara.com> wrote:
>>
>>> On the Future Directions page on the D website, three features are
>>> presented.  One of which is "Mixins", something that I have never heard
>>> of
>>> before.  Would someone care to explain what this is?
>>>
>>> Thanks,
>>>
>>> Craig
>>>
>>
>>I understand it to mean the process of creating a new class by picking out attributes and methods from two or more other classes. A bit like multiple inheritence but instead of getting everything, you get to pick which parts you want to inherit.
>>
>>I could be wrong though.
>>
>>-- 
>>Derek
>
>