Re: [boost] [mixin] Introducing a new library.

Subject: Re: [boost] [mixin] Introducing a new library.
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-01-31 02:30:27

Le 30/01/13 20:53, Borislav Stanimirov a écrit :
> Hello,
>
> Boost.Mixin is a library I'm developing with the idea to someday 
> submit it to Boost.
>
> It is an entity-component system, with full abstraction between 
> interface and implementation.
>
> In short, users can define objects by combining components (often 
> referred to from here on out as mixins). A mixin is a regular C++ 
> class for which two macros are defined. The main thing however are the 
> messages. Instead of getting the component with some function like 
> `get_component` (which is possible but discouraged in the library), 
> users deal with objects only. They can call messages (inspired by 
> Smalltalk's messages) which are dynamically dispatched to the 
> appropriate mixin.
>
> The messages (also defined with macros) are the only thing needed for 
> a user to call methods from the object's mixins. When defining a 
> mixin, the user tells which messages it's going to implement, and when 
> adding this mixin to the object a virtual table of sorts is filled and 
> the object starts responding to those messages by calling the mixin's 
> actual C++ methods.
>
> Some of the key features are:
> * Multicast messages. A message that is implemented and handled by 
> more than one mixin. See the message `trace` in the example. (As 
> opposed to unicast messages, that are handled by a single mixin)
> * Object access from within the mixin. The macro `bm_this` 
> (Boost.Mixin this). See the renderer do in the example.
> * "Live" object mutation by adding and removing mixins. As 
> demonstrated in `change_rendering_system` in the example. This is done 
> via the `object_transformer` class and is currently the only way of 
> adding mixins to objects.
> * Mixin (and message) domains. The domain is a collection of mixins 
> and messages that work together. If you create a set of mixins that 
> will never conceivably have to exist in the same object as another set 
> of mixins, you should use a different domain.
>
> Here is a github link to the library: http://github.com/iboB/boost.mixin
> A working example can be found here: 
> http://github.com/iboB/boost.mixin/tree/master/libs/mixin/example/basic
>
Hi,

IIUC your library is related to the subject-role [1] but a mixin is more 
an aspect of an entity than a role.

Could the user define a typed subjects, that is an entity that have some 
specific mixins?
Could the user see an object restricted to some of his mixins?

Best,
Vicente

[1] Roles :Conceptual Abstraction Theory 
& Practical Language Issues