Fully dynamic d by opDotExp overloading

[downs]

Andrei Alexandrescu wrote:
> Denis Koroskin wrote:
>> On Fri, 17 Apr 2009 18:24:04 +0400, Steven Schveighoffer
>> <schveiguy at yahoo.com> wrote:
>>
>>> On Fri, 17 Apr 2009 09:44:09 -0400, Leandro Lucarella
>>> <llucax at gmail.com>  wrote:
>>>
>>>> I don't fully understand the example though. In writefln((v.qq = 5).i),
>>>> how is that B.i is assigned to 5 if the opDotExp("qq", 5) don't 
>>>> propagate
>>>> the 5 to the new B()?
>>> I think it translates to
>>>
>>> opDotExp("qq") = 5
>>>
>>> Without knowing the signature of qq, how is the compiler supposed to 
>>> infer that it is a property?  In fact, I think this might be a 
>>> limitation of this syntax, you can't define dynamic properties.
>>>
>>> I for one, can't really see a huge benefit, but then again, I don't 
>>> normally work with dynamic-type langauges.  It looks to me like a
>>> huge  hole that the compiler will ignore bugs that would have been
>>> caught if  the methods were strongly typed:
>>>
>>> class c
>>> {
>>>    void opDotExp(char[] methodname,...)
>>>    {
>>>       if(methodname == "mymethod")
>>>          callMyMethod();
>>>       else
>>>          throw new Exception("bad method name: " ~ methodname);
>>>    }
>>> }
>>>
>>> void foo(c myc, bool rarelySetToTrue)
>>> {
>>>    if(rarelySetToTrue)
>>>      myc.mymethud(); // compiles, will throw runtime exception
>>> }
>>>
>>> Also, how do you overload the return value?  Using this proposal,
>>> you  can't have different dynamic methods that return different types.
>>>
>>> -Steve
>>
>> Here is how it could be done:
>>
>> class C
>> {
>>     auto opDot(string methodName, T... args)(T args) // opDotExp
>> renamed to opDot
>>     {
>>         static if (methodName == "length") {
>>             return _length; // return type is size_t
>>         } else static if (methodName == "resize") {
>>             _resize(args); // return type is void
>>         }
>>     }
>> }
>>
>> This is a great use-case for compile-time "static switch". Can we haz
>> one, please?
> 
> I think the more urgent need is for static loops. At least we have a
> simple workaround for static switch.
> 
> Andrei

Static loops are simple, at least in functions.

import std.stdio;

template Tuple(T...) { alias T Tuple; }
template Repeat(T, int I) { static if (!I) alias Tuple!() Repeat; else alias Tuple!(T, Repeat!(T, I-1)) Repeat; }

void main() {
  foreach (i, bogus; Repeat!(void, 15))
    writefln(i);
}