Re: Aliasing or referencing assignment

[David Trudgett <wpower@zeta.org.au.nospamplease>]

Ludovic Brenta <ludovic@ludovic-brenta.org> writes:

> David Trudgett <wpower@zeta.org.au.nospamplease> writes:
>> Without knowing the details of how they work, I was just assuming
>> they would be pre-elaborated during the compilation process.
>
> Internally, they may be implemented by an array and a used length.
> When the used length grows beyond the length of the array, the array
> is reallocated to grow in size.  

I suppose that's the general idea I had in the back of my mind.


> The complexity of this is probably just above what can be
> preelaborated automatically.

It might be tricky, but I'm no compiler writer, so I'll keep my mouth
shut! ;-)


>
> You can have preelaborated unbounded strings if they are constant and
> you declare them in a package which is preelaborated, e.g.

That's useful to know. Thank you.


>
> with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
> package Constants is
>    pragma Preelaborate; -- or better yet, Pure
>
>    function "+" (R : in String) return Unbounded_String
>       renames To_Unbounded_String;
>
>    S : constant Unbounded_String := +"Some fixed string";
> end Constants;
>
> HTH

Yes, it is helpful, thanks. I also like the way you've renamed
To_Unbounded_String to a right associative "+". Very interesting
indeed. Another person posted a code snippet showing a long package
name being renamed to something shorter. It seems 'rename' has more
uses than I at first thought... :-)


>
> (The above package can be declared Pure.  In addition to being
> preelaborated, Pure packages promise that they have no side effects:
> no visible global variables, no access parameters, and no use of
> System.Address.).

I'll keep it in mind the next time I have need of some purity! ;-)

Thanks again for your comments.

David



-- 

David Trudgett
http://www.zeta.org.au/~wpower/

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