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From: "Luke A. Guest" <laguest@n_o_p_o_r_k_a_n_d_h_a_m.abyss2.demon.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: Access type conversions, how?
Date: Tue, 13 Apr 2004 23:51:50 +0100
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User-Agent: Pan/0.14.2 (This is not a psychotic episode. It's a cleansing
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Date: 2004-04-13T23:51:50+01:00
List-Id: <comp.lang.ada>

Well, in answer to my question:

with Unchecked_Conversion;
...
type FloatPtr is access all Float;
	  
function Float_To_GLfloat is new Unchecked_Conversion(Source => FloatPtr, Target => GL.GLfloatPtr);
...
GL.glMultMatrixf(Float_To_GLfloat(M(M'First)'Unchecked_Access));

And all is well.

Luke.