Bill Baxter wrote:
> On Fri, Aug 21, 2009 at 10:36 AM, div0<d...@users.sourceforge.net> wrote:
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>>
>> Not sure what the original choice was based on, but what you suggest
>> looks wrong to me. You aren't necessarily using a template in order to
>> mix it in somewhere.
>>
>> With that syntax it looks like you can only use foo as a mixin. If you
>> change 'mixin' to 'paste' your way round looks even more wrong.
>
> At least for templates that are just a bunch of alias declarations, it
> can be handy to be able to use directly or to mix in. So there would
> be little to be gained by forcing the developer to choose "mixin" or
> "regular template" up front.
>
> For example
>
> template MeshTypes(MeshType) {
> alias MeshType mesh_type
> alias typeof(MeshType.vertices[0]) vert_type;
> alias typeof(MeshType.vertices[0].x) float_type;
> const uint vert_dim = vert_type.length;
> }
>
> That's handy to use inline like MeshTypes!(MyMesh).vert_type
> Or you can mix it in to another class that uses mesh a lot to have all
> those types defined inside your class too.
>
> --bb
Alright, good example.
But then why not:
mixin MeshTypes(MeshType) {
alias MeshType mesh_type
alias typeof(MeshType.vertices[0]) vert_type;
alias typeof(MeshType.vertices[0].x) float_type;
const uint vert_dim = vert_type.length;
}
template MeshTypesOf(MeshType) {
mixin MeshTypes!(MeshType);
}
Admittedly it is not as clean and violates DRY some. But it does allow
the declarer to explicitly determine how the template/mixin gets used.
Eh, I was kinda hoping for a reason better than "there are some cases
where you want both a mixin and a template to be the same thing." I
thought it might be something obvious to someone; something that I
missed. Nonetheless, the template/mixin duality seems fairly benign, so
this decision is starting to look somewhat arbitrary to me.
