static arrays becoming value types

[Leandro Lucarella]

language_fan, el 20 de octubre a las 19:19 me escribiste:
> >> One nasty thing about D's structs is that they don't have structural
> >> equivalence relation unlike tuples. So you need to use the same
> >> container struct type to get the same semantics. To achieve that you
> >> would need some kind of STuple on standard library level or other kinds
> >> of hacks.
> >> 
> >> What I find unfortunate in D is that your abstractions come in two
> >> sizes - either you use the modest tiny construct that does not scale
> >> elegantly or the enormous hammer to crush things down theatretically.
> > 
> > I don't understand very well what are you saying anyways...
> 
> Because of the unnecessary nominal typing in D's tuple emulation, 
> redefinitions of Tuples do not have implicit equivalence relation:
> 
>   struct Tuple(T...) {
>     T t;
>   }
>   struct Tuple2(T...) {
>     T t;
>   }
> 
>   void main() {
>     Tuple!(int,int) a;
>     Tuple!(int,int) b;
>     Tuple2!(int,int) c;
> 
>     assert(a == b); // ok
>     assert(a != c); // Error: incompatible types for ((a) != (b))
>   }
> 
> In some other language:
> 
>   val a = (1,2) : [Int,Int]
>   val b = (1,2) : [Int,Int]
>   val c = (2,3) : [Int,Int]
> 
>   assert(a == b); // ok
>   assert(a != c); // ok
> 
> Did you get it now?

Yes, thanks for the clarification.

> Real tuple types do not have a special type tag which gets injected 
> implicitly with structs. So every time you try to do something 
> lightweight by emulating tuples, you need to refer to the global Tuple 
> type or bang your head to the wall.

Yes, D support for tuples is way far from ideal.

-- 
Leandro Lucarella (AKA luca)                     http://llucax.com.ar/
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