More specific instantiations

[Marco Leise]

Am 14.02.2012, 15:46 Uhr, schrieb Timon Gehr <timon.gehr at gmx.ch>:

> It cannot be a compiler optimization because it potentially changes the  
> semantics of the code:
>
> template T(U, V, W){
>      @templated(W) W idx;
> }
>
> void main(){
>      T!(int,double,long).idx = 1;
>      assert(T!(double,int,long).idx == 1);
> }

Ah right, I was a bit off-topic then: @templated removes duplicate static  
data (if desired) whereas the code gen optimization removes duplicate code  
(automatically). Can we make this distinction at least, or did I miss  
something else? The initial post by bearophile was about both - code and  
data, and I argue that the compiler can figure out which code/methods are  
duplicates, which would be preferred over doing it manually.

These uses would remain:

template T(U, V, W) {
     @templated(W) W idx;
}

struct Foo(U, V, W) {
     void bar() { // one method per W
         @templated(W) static W value;
     }
     void foobar() { // one method per U, V, W
         static W value;
     }
}

while this would be invalid:

struct Foo(U, V, W) {
     @templated(W) void bar() {
         static W value;
     }
}

The reasons are that it could duplicate a safe compiler optimization if  
used on methods and I think @templated is easier to understand if it only  
applies to static data.

-- Marco