Re: [boost] Re: Re: quantity libraries

From: Anatoli Tubman (anatoli_at_[hidden])
Date: 2001-08-30 12:50:45

On Thursday 30 August 2001 20:33, Ken Shaw wrote:

> As I'm sure the guys at JPL thought when different groups mixed radians and
> seconds of arc in the guidance software for the Mars Climate Orbiter.

Do you have any evidence about JPL using some sort of quantity library?
I suspect they used bare doubles or whatever they are called in Ada.
This *is* the sort of thing a quantity library should prevent.

> I think it should restrict the user to one set of measures or the other
> with no mixing or conversion possible. Allowing both in the same
> calculation will insert conversion errors because of the inherent
> dissimularities of the 2 systems.

As long as the conversion is explicit (and is called 
dangerous_inexact_unit_conversion<pounds_force>(kilogram) :) there's no 
problem.

If you don't provide a conversion, then there *is* a problem, because the
user will provide one for himself -- incorrectly.
-- 
anatoli at ptc dot com -- opinions are mine