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From: Dale Stanbrough <dale@goanna.cs.rmit.EDU.AU>
Subject: Re: 'size attribute inheritance
Date: 1997/08/14
Message-ID: <5t018b$g3o$1@goanna.cs.rmit.edu.au>#1/1
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References: <33ECF679.4B5D@lmco.com>
 <mheaney-ya023680001308972242460001@news.ni.net>
 <mheaney-ya023680001308972232470001@news.ni.net> <EEwvGB.DD5@world.std.com>
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Organization: Royal Melbourne Institute of Technology
Newsgroups: comp.lang.ada
Date: 1997-08-14T00:00:00+00:00
List-Id: <comp.lang.ada>


Matthew Heaney, mheaney@ni.net writes:
 I wouldn't suggest giving up strong typing completely, only at the
 interface layer of the system, where you're touching the metal (ie whenever
 you write O'Address).  Whatever data an interface abstraction presents to
 the rest of the system should be strongly typed, but I recommend that in
 the implementation of that abstraction, weak types be used to read in the
>data, and that the range of the input data be checked manually.


I would still use strong typing even at this level. Obviously out of range
values are a big problem, so don't declare types that could have out of range
values.

E.g. if you are reading in a 12 bit value from an A/D then declare...


	type AD_Reading is mod 2**12;


You still get the benefits of strong typing (can't accidentally convert to
an appropriately scaled/biased value) and no risk of Constraint_Error.


Dale