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From: Phil Clayton <phil.clayton@lineone.net>
Newsgroups: comp.lang.ada
Subject: Re: Array initialization in SPARK
Date: Sat, 30 Oct 2010 06:11:41 -0700 (PDT)
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Date: 2010-10-30T06:11:41-07:00
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On Oct 30, 9:10=A0am, AdaMagica <christoph.gr...@eurocopter.com> wrote:
> On 30 Okt., 03:04, Phil Clayton <phil.clay...@lineone.net> wrote:
>
> > ... =A0We
> > could then write something like:
>
> > =A0 Out_Matrix :=3D
> > =A0 =A0 =A0Matrix'(for I in Natural range Out_Matrix'Range(1) =3D>
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0(for J in Natural range Out_Matrix'Range=
(2) =3D>
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 In_Matrix(J, I)));
>
> But we would need an assertion that 'Range(1) equals 'Range(2), else
> we would get Constraint_Error. (Equal lengths would not suffice - no
> sliding there.)

Yes, you would need Out_Matrix'Range(1) =3D In_Matrix'Range(2) and vice-
versa.
I actually meant to write:

  Out_Matrix :=3D
     Matrix'(for I in Natural range In_Matrix'Range(2) =3D>
               (for J in Natural range In_Matrix'Range(1) =3D>
                  In_Matrix(J, I)));

which still requires the same assertions.  However, this r.h.s. could
be used as the return value of a Matrix_Transpose function which would
enable us to avoid such assertions because we don't have to specify
the unconstrained array size independently, e.g.

  Out_Matrix : Matrix :=3D Matrix_Transpose(In_Matrix);

I suppose this is a more 'functional' style of Ada...

Phil