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From: ytomino <aghia05@gmail.com>
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Subject: Re: discriminant questions
Date: Tue, 20 Sep 2011 16:28:55 -0700 (PDT)
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Date: 2011-09-20T16:28:55-07:00
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(To avoid confusion, I do not use names of "Get" and "Set".)

function Element (C : Container) return Element_Type;
function Set_Element (C : Container; New_Item : Element_Type);

These functions may copy Element_Type.
It's futile cost if Element_Type'Size is large.

function Element (C : Container) return access constant Element_Type;

It's dangerous. the reason is written in AdaCore Gem #107.

procedure Query_Element (C : Container; Process : access procedure
(Item : in Element_Type));
procedure Update_Element (C : Container; Process : access procedure
(Item : in out Element_Type));

These procedures are better than above functions.
No copy, no dangerous.
But, we must make nested subprogram, so source code may be verbosity.

function Constant__Reference (C : Container) return
Constant_Reference_Type;
function Reference (C : Container) return Reference_Type;

These functions give same effects as Query_Element and Update_Element.
And These are simple to use.

In fact, Element, Set_Element, Query_Element and Update_Element are
able to be implemented with Reference.
The reverse is impossible.

Therefore I think Constant__Reference and Reference are more better
functions ... aside from primitive or not.
I also understand your feeling because the mechanism of accessor is
complex a little to call primitive.
But accessor is a nice idea, not kludge.