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From: lmiller@indyvax.iupui.edu
Newsgroups: comp.lang.ada
Subject: Re: Types with physical dimension
Message-ID: <1994Oct3.210603.8801@ivax>
Date: 3 Oct 94 21:06:03 -0500
References: <INFO-ADA%94092805521945@VM1.NODAK.EDU>
Date: 1994-10-03T21:06:03-05:00
List-Id: <comp.lang.ada>

Stephe Leake at NASA GSFC (NBSSAL@stdvax.gsfc.nasa.gov) worked on something
like this some years ago.  I never worked with the packages produced but was
told by Stephe that the huge number of types generated made for long compile
times on good compilers and vast ugly deaths on poor ones.  His final analysis: 
neat, but not quite worth the effort.  For cartesian and other multi
dimensional stuff I found creating types which reflected reality quite useful
in pointing out errors at compile time.  Overloading the operators then made
for very readable expressions in code.  

type CART_AXES is (X, Y, Z);
type POLAR_AXES is (Lat, Long, Radius);
-- continue for all helpful coordinate systems...

type CART_VECTORS is array (CART_AXES) of Float;
type POLAR_VECTORS is array (POLAR_AXES) of Float;


Then the compiler will always kick you in the shin if you try to add
cart_vectors and Polar_Vectors without defining the proper operators.  One can
just imagine all of the opportunities C provides to make multitudes of mistakes
related to this situation.