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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Safety-critical development in Ada and Eiffel
Date: 1997/07/17
Message-ID: <dewar.869181695@merv>#1/1
X-Deja-AN: 257469336
References: <EDEnp2.1K3@syd.csa.com.au> <EDGE3J.213@syd.csa.com.au>
Organization: New York University
Newsgroups: comp.object,comp.software-eng,comp.lang.ada,comp.lang.eiffel
Date: 1997-07-17T00:00:00+00:00
List-Id: <comp.lang.ada>


Don Harrison says

<<Yes, I should have realised! It's the old workaround to the infuriating Ada83
visibility problem of not being able to see the predefined operators of a user-d
efined(?) type in client code. In spite of already with-ing the
supplier module (which I don't think you should have to do, anyway - if you
*use* features exported by a package, explicitly importing it is redundant),
you can't see (hence, use) the imported operators.
>>


My goodness, surprising that anyone would think this, but then I guess there
are people who really prefer uncontrolled anarchy.

To me one of the real advantages in Ada is that you know right away, right
at the start of the package, exactly what services are being used, and
you can more easily excercise control over this. If you let code anywwhere
reach anywhere easily, you have a recipe for mess.

The requirement to write a with clause is also the requirement to think
about whether it is appropriate for the unit you are in to "with" the
unit that you think you need.

As for the "infuriating" Ada 83 visibility "problem". I always found this
odd. I understand that people do not like to use "use" because, especially
with poor tools, they want to be easily able to tell where somethintg
comes from, but I never understood why this perfectly understandable
reasoning does not apply to operators (personally I prefer to use "use"
most of the time anyway).