C++0x Concepts - Dead?

[Walter Bright]

aarti_pl wrote:
> Walter Bright pisze:
>> aarti_pl wrote:
>>> My proposal would make meta programing in D much more intuitive 
>>> (because of using rules - not bunch of corner cases as it is today). 
>>> Unfortunately almost no one from NG commented on that...
>>
>> Thank you, but I don't see in your proposal a method that can:
>>
>> 1. instantiate templates only if a value argument is prime or odd.
>>
>> 2. instantiate templates only on a type which supports addition and 
>> has the method foo.
>>
>> Note that C++ Concepts could do (2) but could not do (1).
> 
> ad.1
> 
> template normalizedType((T U N : U[N=size_t]) && (N & 1))
> 
> As it is stated in proposal commas are only syntax sugar for more 
> general form with '&&'.

How do you distinguish a type from an expression?


> ad.2.
> 
> This case is in fact the same as 1. Because of the fact that A, B, C <=> 
> A && B && C, you can create expressions as you want just using second 
> form with logical operators. In this case you should just use proper 
> compile time reflection mechanism in D to get information about type 
> properties.

class C {
     int opAdd(C);
}

How would I write the parameter to accept any type that supports 
addition? I want to support int, float, C, etc., without having to 
exhaustively enumerate them.