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From: Fraser Wilson <newsfraser@blancolioni.org>
Newsgroups: comp.lang.ada
Subject: Re: Announce: Grace project site operational
Date: 17 May 2002 18:41:17 +0200
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Darren New <dnew@san.rr.com> writes:

> area=length*length is easy. volume=length*length*length is harder, because
> you would need to automatically generate the intermediate type involved in
> the volume. I.e., if "area" weren't defined, how would you define operator
> "*"(l,r : length)?

The short answer is that you make sure you do define area.  I restrict
new dimensions to a maximum of two base dimensions; though you can
have more than one way of constructing them; e.g.

    Energy in Joules is Force * Length or Power * Time;

but you can't say Acceleration is Length / Time / Time, for the reason
you mention above.

Here's why I love Ada: given definitions for length, area in terms of
length and volume in terms of length and area, you can multiply three
lengths together and automagically have a volume return type.  I
suspect that much more of this sort of carrying on will make the
compiler run noticeably slower though.

Fraser.