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From: mfeldman@seas.gwu.edu (Michael Feldman)
Newsgroups: comp.lang.ada
Subject: Re: Pre-condition vs. Post-condition
Message-ID: <2937@sparko.gwu.edu>
Date: 26 Mar 91 23:36:40 GMT
References: <20600091@inmet> <23141@as0c.sei.cmu.edu> <2918@sparko.gwu.edu> <2929@sparko.gwu.edu> <5074@goanna.cs.rmit.oz.au>
Reply-To: mfeldman@seas.gwu.edu ()
Organization: The George Washington University, Washington D.C.
List-Id: <comp.lang.ada>

O'Keefe's posting gave such a good discussion of the issues that there's not
much to add, except the following:

The whole thread started with preconditions. I think Ada has a chance to
make life a whole lot easier by making it _possible_ to initialize all
types with default initial values, consistently. I am not interested in
having clients depend upon the initial values; rather I want clients
to be able to depend on variables, types, whatever, _not_ being
_uninitialized._ There will always be something in there that's
"in-range" for the type. Clearly Ada83 thought this was worth doing for
access types, and look how much easier it is to write linked-list
packages because there are no garbage pointers to worry about (leave
aside the dangling-pointer problem left unsolved by Unchecked_Deallocation!)

I was told once by an Ada83 high priest that the reason record fields can
be initialized is that, syntactically, it's "free" because the syntax
of a field declaration is the same as the syntax of a variable declaration.
I got the impression that the thinking didn't go much deeper than that.
They didn't bother with initializers for other types because it wasn't free.

Mike