Objective-D, reflective programming, dynamic typing

[Georg Wrede]

Andrei Alexandrescu wrote:
> Christopher Wright wrote:
>> Andrei Alexandrescu wrote:
>>> Jarrett Billingsley wrote:
>>>> On Fri, Apr 3, 2009 at 11:20 AM, Andrei Alexandrescu
>>>> <SeeWebsiteForEmail at erdani.org> wrote:
>>>>
>>>>>> You can't.  D's varargs suck.
>>>>> Of course you can. Where did that come from?
>>>>>
>>>>> void foo(T...)(T args) { bar(args); }
>>>>> void bar(T...)(T args) {  foreach (a; args) writeln(a); }
>>>>
>>>> *NOT* the same thing.  They are templated, which means a new
>>>> instantiation for each different combination of argument types, and
>>>> cannot be virtual.  Please keep that in mind.
>>>
>>> But my point was that variadic templates can be ideal wrappers for 
>>> the non-templated variadics, which can be virtual. It's the best of 
>>> both worlds, you get no bloating and comfortable calling syntax too.
>>>
>>> I think it's silly to ask "I want to do... xyz... but without 
>>> templates because templates aren't virtual/cause bloating/bring up 
>>> painful memories". Templates are an excellent starting point in many 
>>> designs because they preserve full typing of the parameters. Then, of 
>>> course you can route them to dynamic functions no problem.
>>
>> Okay, so before I had to write:
>>
>> void foo(...)
>> {
>>    foo(_argptr, _arguments);
>> }
>> void foo(void* argptr, TypeInfo[] argtypes) {}
>>
>>
>> You want me to instead write:
>>
>> // needs a different name due to overload issues
>> void foo_templated(T...)(T args)
>> {
>>    foo(args);
>> }
>> void foo(...)
>> {
>>    foo(_argptr, _arguments);
>> }
>> void foo(void* argptr, TypeInfo[] argtypes) {}
>>
>> How the hell does that help?
> 
> void foo_templated(T...)(T args)
> {
>    Variant[args.length] dynatyped;
>    foreach (i, arg; args) dynatyped[i] = arg;
>    return foo(dynatyped);
> }
> void foo(Variant[] dynatyped...)
> {
>    ...
> }


Nice idiom! Wish I could templatize this template, or sugarize this syntax.