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From: "martin.m.dowie" <martin.m.dowie@ntlworld.com>
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Subject: Re: Safe Units Handling in Ada
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Date: Thu, 23 May 2002 17:48:06 +0100
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Date: 2002-05-23T17:48:06+01:00
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"Dan Andreatta" <andreatta@mail.chem.sc.edu> wrote in message
news:338040f8.0205230757.2150b881@posting.google.com...
> > The generated example.ads yields:
> > ...
> >    function "*"
> >      (Left  : Kilogram;
> >       Right : Kilogram)      -- This is good, we want it abstract.
> >      return Kilogram
> >    is abstract;
> >
>
> This also should return kg**2.

Can you set this up as another rule?

My own attempt at a Unit Generator package was allowed
users to define:
   a) which of the SI base units they wanted
   b) which of the SI derived units they wanted
   c) to define alias (ie subtypes, e.g. "subtype Area is Metre_Squared;")
of any unit
   d) to define a range of powers

This lead to a package such as:

generic
   type A_Float is digits <>;
package SI_Units is

   type Unitless is new A_Float;

   type Metre is new A_Float;
   type Metre_Squared is new A_Float;
   type Metre_Cubed is new A_Float;

   function "*" (L : Metre; R : Metre) return Metre_Squared;
   ...
end SI_Units;

The problem I found with this approach was one of line numbers when
all units are requested for the range **-3 .. **+3. Some code browsers
don't seem to like file >1200 lines long!