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From: mdash@mh3bc1.UUCP (M.D.Scheer)
Newsgroups: net.lang
Subject: Re: declarations and nested blocks
Message-ID: <112@mh3bc1.UUCP>
Date: Wed, 21-Dec-83 16:08:06 EST
Article-I.D.: mh3bc1.112
Posted: Wed Dec 21 16:08:06 1983
Date-Received: Fri, 23-Dec-83 01:29:21 EST
References: <1072@mit-eddie.UUCP>, <749@sdcrdcf.UUCP>
Organization: Bell Labs, Murray Hill
Lines: 17


Of course, Ada for loop iterators are implicitly declared, but
this does not solve the general problem of unintenionally modifying
variables inherited from outer scopes.

One solution is to use naming conventions like P_X (subject this
construct to the lexical restrictions of your favorite programming
language) for the variable X declared in procedure P.  This would
solve the majority of >accidents< arising from implicit inheritance
in nested scopes.

Many of the >problems< arising in nested scopes are not accidents,
though.  Simple nesting is simply an inadequate form of program organization
and makes certain problems unavoidable.  For a nice discussion of the
problems of nested organization, see the paper by Clarke, Wileden,
and Wolf, "Nesting in Ada Programs is for the Birds," SIGPLAN Notices,
v.15, #11, November 1980.