From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,5d708145f98f6273
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2004-04-12 18:25:41 PST
Path: 
 archiver1.google.com!news1.google.com!news.glorb.com!wn51feed!worldnet.att.net!216.168.1.162!sn-xit-02!sn-xit-01!sn-post-01!supernews.com!corp.supernews.com!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Access type conversions, how?
Date: Mon, 12 Apr 2004 20:25:23 -0500
Organization: Posted via Supernews, http://www.supernews.com
Message-ID: <107mgcjspsour11@corp.supernews.com>
References: 
 <pan.2004.04.13.00.32.33.603741@n_o_p_o_r_k_a_n_d_h_a_m.abyss2.demon.co.uk>
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4910.0300
X-Complaints-To: abuse@supernews.com
Xref: archiver1.google.com comp.lang.ada:7028
Date: 2004-04-12T20:25:23-05:00
List-Id: <comp.lang.ada>

"Luke A. Guest" <laguest@n_o_p_o_r_k_a_n_d_h_a_m.abyss2.demon.co.uk> wrote
in message
news:pan.2004.04.13.00.32.33.603741@n_o_p_o_r_k_a_n_d_h_a_m.abyss2.demon.co.
uk...
> Hi,
>
> We have the following in our GL package:
>
> package C renames Interfaces.C;
> ...
> type GLfloat      is new C.C_float;
> ...
> type GLfloatPtr   is access all GLfloat;
> ...
> procedure glMultMatrixf(M : in GLfloatPtr);
>
> Now, in my code, I've created a Matrix package which has as it's type:
>
> type Object is array(Integer range 0 .. 15) of aliased Float;
>
> Now, I've made it aliased because I want to pass this to glMultMatrixf,
> but for some reason I cannot work out exactly how to do it.
>
> I've tried all sorts, like:
>
> GL.glMultMatrixf(M(M'First)'Unchecked_Access); -- Wrong type
>
> I've tried casting it to GL.GLfloat and GL.GLfloatPtr, but nothing's
> working. Can anyone help?

Ready for a head slapping moment? :-)

GLfloatPtr points at a GLFloat (a C.C_Float), the 'Unchecked_Access points
at a (Standard.)Float. These aren't the same type! They don't even need to
be the same size (although they will be in practice), so you can't convert
the access type.

If Object was declared "... of aliased GLFloat" everything should be fine.

(You can slap your head and go "Duh!" now. :-)

                 Randy.