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Path: utzoo!attcan!uunet!husc6!linus!mbunix!eachus
From: eachus@mitre-bedford.ARPA (Robert Eachus)
Newsgroups: comp.lang.ada
Subject: Re: Typing Ada
Summary: What about generics, tasks and subprograms?
Keywords: graphical design, structures, abstraction
Message-ID: <32982@linus.UUCP>
Date: 26 May 88 14:14:51 GMT
References: <12400764147.13.RCONN@SIMTEL20> <25135.580491166@mbunix> <1017@cresswell.quintus.UUCP> <2831@Shasta.STANFORD.EDU>
Sender: news@linus.UUCP
Reply-To: eachus@mbunix (Robert I. Eachus)
Organization: The MITRE Corporation, Bedford, Mass.
List-Id: <comp.lang.ada>


	[In Memorandum. The line eater, may he rest in peace.]

In article <2831@Shasta.STANFORD.EDU> neff@Shasta.UUCP (Randall Neff) writes:
(Some stuff omitted for brevity)
>
>In Ada, there is only a single hierarchy mechanism, the package; and only
>a single abstraction, the programming language code.
>
    To quote the Ada RM:

    Packages are one   of the four  forms  of program  unit of   which
programs can  be  composed.  The  other forms  are   subprograms, task
units, and generic units. Chapter 7, paragraph 1.

    All four are heirarchy mechanisms, all four  can be used  to model
abstractions (although each is most appropriate for a different set of
abstractions).   I'm sure   Randall's  omission   of other   hierarchy
mechanisms  was   accidental, but there  are many  Ada programmers out
there who don't seem to realize that generics and tasks can, and often
should, be used to create abstact data types,  so I couldn't  let this
just pass by.  (Just in case  someone decides  to  pick nits, Ada also
has blocks which can be considered as a heirarchy mechanism.  But they
are in general not used in that way, and should be excluded also based
on the sense of Randall's discussion.)


					Robert I. Eachus

with STANDARD_DISCLAIMER;
use  STANDARD_DISCLAIMER;
function MESSAGE (TEXT: in CLEVER_IDEAS) return BETTER_IDEAS is...