static arrays becoming value types

[Leandro Lucarella]

language_fan, el 20 de octubre a las 13:52 me escribiste:
> Tue, 20 Oct 2009 10:34:35 -0300, Leandro Lucarella thusly wrote:
> 
> > dsimcha, el 20 de octubre a las 02:44 me escribiste:
> >> == Quote from Walter Bright (newshound1 at digitalmars.com)'s article
> >> > Currently, static arrays are (as in C) half-value types and
> >> > half-reference types. This tends to cause a series of weird problems
> >> > and special cases in the language semantics, such as functions not
> >> > being able to return static arrays, and out parameters not being
> >> > possible to be static arrays.
> >> > Andrei and I agonized over this for some time, and eventually came to
> >> > the conclusion that static arrays should become value types. I.e.,
> >> >    T[3]
> >> > should behave much as if it were:
> >> >    struct ??
> >> >    {
> >> >       T[3];
> >> >    }
> >> > Then it can be returned from a function. In particular,
> >> >    void foo(T[3] a)
> >> > is currently done (as in C) by passing a pointer to the array, and
> >> > then with a bit of compiler magic 'a' is rewritten as (*a)[3]. Making
> >> > this change would mean that the entire array would be pushed onto the
> >> > parameter stack, i.e. a copy of the array, rather than a reference to
> >> > it. Making this change would clean up the internal behavior of types.
> >> > They'll be more orthogonal and consistent, and templates will work
> >> > better. The previous behavior for function parameters can be retained
> >> > by making it a ref parameter:
> >> >     void foo(ref T[3] a)
> >> 
> >> Vote++.  It's funny, I use static arrays so little that I never
> >> realized that they weren't passed by value to functions.  I'd
> >> absolutely love to be able to just return static arrays from functions,
> >> and often use structs to do that now, but using structs feels like a
> >> really ugly hack.
> > 
> > It would be the poor men tuple for returning (homogeneous) stuff =P
> 
> It depends on how you define things. Traditionally tuples are seen as a 
> generalization of pairs (2 elements -> n elements). Records, on the other 

In what tradition? C++ maybe. I never saw a pair type outside C++, but saw
tuples everywhere (even in other structured languages like SQL).

> hand, are generalization of tuples (simple number index -> named 
> elements). You need couple of additional layers of generalization to come 
> up with structs (subtyping, member functions, generics etc.)
> 
> 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...

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