C++ guys hate static_if?

[deadalnix]

On Tuesday, 12 March 2013 at 02:39:06 UTC, TommiT wrote:
> On Saturday, 9 March 2013 at 16:42:56 UTC, deadalnix wrote:
>> On Saturday, 9 March 2013 at 15:22:55 UTC, monarch_dodra wrote:
>>> [..]
>>> BTW, in regards to template constraints (not the rest), he 
>>> does have a point. We have raised the exact same issues here 
>>> on the boards more than once.
>>
>> The more I think of it, the more this whole duck typing for 
>> templates is probably a bad solution because we lack tool to 
>> express « meta types ».
>
> I'm starting to think so too.
>
> On Saturday, 9 March 2013 at 18:46:23 UTC, Peter Alexander 
> wrote:
>> [..]
>> I suppose a better solution to this problem would involve 
>> someway of specifying that random access ranges are a subtype 
>> of input ranges, and the overload resolution would recognise 
>> that the random access range version is preferable to the more 
>> general version when available.
>
> I wonder how would these "polymorphic concepts" work exactly. 
> The following is pseudo-code:
>
> concept A1 {
>     void foo();
> }
>
> concept A2 : A1 { // A2 extends A1
>     void bar();
> }
>
> concept B1 {
>     void fun();
> }
>
> concept B2 : B1 {
>     void gun();
> }
>
> struct S1 implements A2 {
>     void foo() { }
>     void bar() { }
> }
>
> struct S2 implements B2 {
>     void fun() { }
>     void gun() { }
> }
>
> void dostuff(A1, B1)(A1 a, B1 b) { } // Overload-1
> void dostuff(A2, B1)(A2 a, B1 b) { } // Overload-2
>
> void main() {
>     S1 s1;
>     S2 s2;
>     dostuff(s1, s2); // calls the more specialized Overload-2
> }
>
> // But, if we add the following overload, then the above
> // function call dostuff(s1, s2) doesn't know whether to
> // call Overload-2 or, the equally specialized, Overload-3:
>
> void dostuff(A1, B2)(A1 a, B2 b) { } // Overload-3
>
> // And, if we add yet another, more specialized, overload,
> // then the previous ambiguity goes away:
>
> void dostuff(A2, B2)(A2 a, B2 b) { }

Yes, that is the idea. It seems really cool.