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From: Fraser <newsfraser@blancolioni.org>
Newsgroups: comp.lang.ada
Subject: Re: Safe Units Handling in Ada
Date: Thu, 23 May 2002 12:16:51 +0200
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Date: 2002-05-23T10:17:45+00:00
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Stephen Leake wrote:

 > I've done some thinking about how this will integrate with my
 > Robotics code, and I'll need Cartesian vectors with units. I
 > currently have:

[code snipped]

 > Now I'll have to have Meters_Cart_Vector_Type and
 > Velocity_Cart_Vector_Type, etc, with associated operations. Time will
 >  remain a scalar :).
 >
 > Any thoughts on extending macks to output that?

Someone will have to remind me how the cross product is calculated!

This is just off the top of my head:

    unit Meters_Type;
    unit Seconds_Type;
    unit Velocity_Type is Meters_Type / Seconds_Type;

    vector Meters_Cart_Vector_Type is Meters_Type * 3;
    vector Velocity_Cart_Vector_Type is Velocity_Type * 3;

There would have to be some sort of syntax for specifying the vector
index type (or to ask for a record type instead).  The operators + and - 
(binary and unary) would be provided, as well as a cross product if it's 
a 3 vector, and a dot product in any case.

Maybe we don't need a vector keyword, since it's implied by the syntax 
"identifier operator constant-integer", but on the other hand there's no 
need to worry about keyword bloat in a language of this size.

 > I like the origin of "macks"; it warms my physics nerd heart :). Be
 > sure to put it in the package somewhere.

Thanks!  I was pretty tickled when I realised the letters spelled a word 
(sort of).

Fraser.