Re: Efficient Matrix?

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Adrian Knoth <adi@drcomp.erfurt.thur.de> writes:

> Robert A Duff <bobduff@shell01.TheWorld.com> wrote:
> 
> > Compilers are required to pack tightly in this case (one bit per Boolean
> > component).  I.e., Matrix'Component_Size will be 1 if there's a pragma
> > Pack.  See RM-13.2(9).
> 
> Hmm?

Looks like a compiler bug to me.  It seems to me that RM-13.2(9) implies
packed arrays of Boolean have 'Component_Size = 1.  Don't you think so?

> with Ada.Text_IO; use Ada.Text_IO;
> 
> procedure bla is
> 
>    type MATRIX is array (Positive range <>, Positive range <>) of Boolean;
>    type POINTER_MATRIX is access all MATRIX;
> 
>    pragma Pack (MATRIX);
> 
>    type my_matrix is array (Positive range <>, Positive range <>) of Boolean;
> 
>    A : POINTER_MATRIX := new MATRIX (1 .. 10000, 1 .. 5000);
> 
> begin
>    Put_Line (Integer'Image (MATRIX'Component_Size));
>    Put_Line (Integer'Image (my_matrix'Component_Size));
> end bla;
> 
> 
> adi@drcomp:/tmp$ ./bla
>  8
>  8
> adi@drcomp:/tmp$
>  
> > It's got nothing to do with the fact that the thing is heap allocated,
> > nor the fact that the bounds are not known at compile time.
> 
> For the variable A it is even known, but I was not able to determine
> a valuable difference in memory-comsumption.

So what size is A.all?

- Bob