static arrays becoming value types

downs default_357-line at yahoo.de
Mon Oct 19 20:02:04 PDT 2009


Walter Bright wrote:
> 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)

WOO! Thanks! :D



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