Xref: utzoo comp.lang.c:26853 comp.lang.misc:4428
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From: news@ism780c.isc.com (News system)
Newsgroups: comp.lang.c,comp.lang.misc
Subject: Re: C strongly typed?
Message-ID: <39941@ism780c.isc.com>
Date: 13 Mar 90 01:35:56 GMT
References: <259@eiffel.UUCP) <1990Mar1.172526.28683@utzoo.uucp) <849@enea.se) <1990Mar7.182230.5517@utzoo.uucp) <862@enea.se>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 25

In article <862@enea.se> sommar@enea.se (Erland Sommarskog) writes:
>
>Well, apparently I am allowed to mix apples and oranges. If I have
>two types of data that both happens to be represented by integers,
>but have no logical connection what so ever I cannot apparently 
>express that in C. And consequently I cannot take help from the
>compiler to catch inadvertent mixups in for instance procedure calls.
>

I am unaware of any commonly available language that prevents this form of
mistake.  Look at the following:

  double distance;
  double time;
  double velocity;

  velocity = distance/time;  /* this makes sense */
  velocity = distance+time;  /*  I mixed 'apples' and 'oranges' and produced
				 a lemon :-) */

I did read a paper (sorry, I don't have the reference) describing a language
that allowed one to augment the the type declaration with a units declaration
so as to be able to catch errors of this form.

   Marv Rubinstein