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Date: Thu, 4 Oct 2018 14:38:17 -0700 (PDT)
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Subject: A little trouble with very large arrays.
From: Shark8 <onewingedshark@gmail.com>
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Xref: reader02.eternal-september.org comp.lang.ada:54479
Date: 2018-10-04T14:38:17-07:00
List-Id: <comp.lang.ada>

I'm trying to implement a FITS library for work -- see https://fits.gsfc.na=
sa.gov/standard40/fits_standard40aa.pdf -- and have come across some rather=
 interesting problems implementing it.

The main-problem right now is the "Primary Data Array" which can have a dim=
ensionality in 1..999, each itself with some non-zero range. (In the files =
these are specified by keywords in the file like NAXIS =3D n, NAXIS1 =3D n_=
1, NAXIS2 =3D n_2, and so on until the NAXISn =3D n_n keyword/value pair is=
 encountered.)

Relatively straightforward, no? Well, I'd thought I could handle everything=
 with a dimensionality-array and generic like:


    Type Axis_Count is range 0..999 with Size =3D> 10;
    Type Axis_Dimensions is Array (Axis_Count range <>) of Positive
      with Default_Component_Value =3D> 1;
...
Generic
	Type Element is (<>);
	Dim : Axis_Dimensions:=3D (1..999 =3D> 1);
Package FITS.Data with Pure is

	Type Data_Array is not null access Array(
			1..Dim( 1),1..Dim( 2),1..Dim( 3),1..Dim( 4),
  			1..Dim( 5),1..Dim( 6),1..Dim( 7),1..Dim( 8),
  			--...
			1..Dim( 997),1..Dim( 998),1..Dim( 999)
		) of Element
      with Convention =3D> Fortran;
End FITS.Data;

But no dice.
GNAT won't even compile an array like this [999 indexes].


What's the proper way to go about doing this?
(As another interesting constraint, the file-format mandates a sort of bloc=
k-structure of 2880 bytes [23040 bits], and while I don't anticipate this b=
eing an issue, something that might be relevant.)