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Date: 28 Jan 93 01:22:24 GMT
From: kanderso@mabillon.ICS.UCI.EDU (Kenneth Anderson)
Subject: Re: private types and recompilation
Message-ID: <9301271722.aa25516@Paris.ics.uci.edu>
List-Id: <comp.lang.ada>

In comp.lang.ada you write:

>When Ada 83 was designed, why did the designers choose to put
>the details of private types in package specifications, rather than
>in package bodies (which is more in the spirit of information hiding, and
>better supports independent compilation).

I'm not sure, but I think because the compiler needs to know the size
of the types so that it can allocate space for parameters in the
subprograms that are defined in the spec.


>generic
>  type ATOM is private;
>package LIST_ADT is
>  type POSITION is private;
>  type LIST is private;
>  procedure CREATE(L: in out LIST);
>  procedure INSERT_AFTER(L: in out LIST; P: POSITION; A: ATOM);
>  ...

>private
>  type LIST;
>  type POSITION is access LIST;

You only need the previous two lines.  The declaration below can be
hidden in the body of the package.

>  type LIST is record
>    A: ATOM;
>    NEXT: POSITION;
>  end record;
>end LIST_ADT;


>-Dave Erickson

Ken
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Ken Anderson                           |  "I'd much rather live in perfection,
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