Jarrett Billingsley wrote:
On Thu, Mar 12, 2009 at 9:33 AM, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> wrote:
Hello,
I'm looking for a catchy phrase denoting this D idiom:
template Blah(Stuff)
{
alias ... Blah;
}
i.e., defining inside a template a symbol of the same name as the template
itself. Then you can use Blah!(X, Y) to mean Blah!(X, Y).Blah.
What would be a catchy, descriptive, and memorable phrase for this?
...Unnecessary?
You know i have to be contrary :P but I have never found a use for
multiple declarations inside a template _except_ when it's used as a
mixin. Most of the time, I declare exactly one symbol inside the
template, and it's always the same name as the template. Having to
specify the name of the template over and over inside it is a blatant
violation of DRY, easy to mess up (typos, changing the template name
etc.) and is hard to diagnose when you do it wrong, since the compiler
just has no idea what you're trying to do and you end up with all
sorts of confusing errors about voids having no value.
Allowing multiple declarations inside templates looks good in the
spec, but honestly, I only ever use it for mixins. My mixin templates
are also never used as anything other than mixin templates, creating
this sort of split between templates and mixins, even though they're
represented by the same language structure. Mixins are really more
like a limited form of semihygenic AST macro, one which can only
expand to declarations and not arbitrary code structures.
If templates were limited to a single declaration - and mixins were
either changed to a different "type" or replaced outright by macros -
I'd be perfectly happy, and there'd be no need for Implicit Template
Name Forwarding (do you see what I just did there ;) ).
Nice. The problem however is that very, very often I need to store
intermediate results, otherwise the code becomes quickly unreadable or
spread across too many different non-reusable templates. What I now do
is e.g. create a short template Blah(X, Y, Z) that aliases itself to
BlahImpl!(X, Y, Z).Result. Hardly elegant.
I suggested Walter to allow templates using the eponymous trick to be
able to define private symbols.
Andrei
