RE: [boost] Eric Ford's Unit package

From: Paul A. Bristow (boost_at_[hidden])
Date: 2003-03-04 02:48:06

(Reporting including title)  Sorry.  Paul

> This looks most interesting, and there most definitely remains a
> great need for
> a units handling package.
>
> I presume you have looked at W W Brown's SI units proposal
>
> http://home.fnal.gov/~wb/SItempl8.pdf
>
> and wonder why you rejected it and how your proposal is different.
>
> Paul
>
> PS It seems that time gets into global namespace.  I agree it should not be
> there but don't know how to fix it. I hit the same problem in my previous
> (rudimentary) attempt with units.
>
> Paul A Bristow, Prizet Farmhouse, Kendal, Cumbria, LA8 8AB  UK
> [phone]   Mobile [phone]
> Mobile mailto:pabristow_at_[hidden]
> mailto:pbristow_at_[hidden]
>
>
> > -----Original Message-----
> > From: boost-bounces_at_[hidden]
> > [mailto:boost-bounces_at_[hidden]]On Behalf Of Eric Ford
> > Sent: Friday, February 28, 2003 8:46 AM
> > To: boost_at_[hidden]
> > Subject: [boost] (no subject)
> >
> >
> > I decided that I needed a workable units library, so I wrote one.  It
> > allows for weakly typed dimensioned quantities (so a length divided by
> > a time is automatically converted to a velocity).  It also allows
> > users to use strong typeing for quantities of the same dimension which
> > shouldn't be confused (so you don't set a mass of apples equal to a
> > mass of oranges).
> >
> > I attempted to make it pretty general, allowing for all the standard
> > SI dimensions, a dimension for money (since that is something lots of
> > people care about), and I've left one dimension avaliable for users.
> > Fractional powers of dimnensions are allowed.  (It also includes a
> > compile-time fractions header file that might be useful for other
> > purposes.)  Power users could setup units using their own classes
> > for the internal numeric type or even provide their own systems of units.
> >
> > I uploaded the first draft version of it to the vault a ebf_units.zip.
> > I've included several demonstration programs to show how it can be used.
> >
> > example1.cpp demonstrates the use of simple SI units, including arithmetic
> > on such variable and automatic conversion when multiplying or dividing
> > dimensioned quantities.
> >
> > example2.cpp demonstrates how you could use multiple representations
> > (e.g., float and double) in the same program.  I've included extremely crude
> > numeric type promtion mainly for  demonstration purposes.
> >
> > example3.cpp demonstrates the use of multiple systems of units in a
> > single program (e.g., including both standard/si/mks units and
> > "relativistic units where the speed of light is set to unity).
> > SIUnits only allows one in a program.  Any conversions
> > between systems must be made explicitly.
> >
> > example4.cpp demonstrates basic use of "qualifiers".  These allow
> > users to make strongly typed units, so that quantities of the same
> > dimension, but different meaning can't be confused.  (e.g., a mass
> > of apples and a mass of oranges)
> >
> > example5.cpp demonstrates how a user can extend this to allow for
> > some automatic conversions (e.g., automatically convert apples to
> > fruits, but not vice versa, or add apples and oranges and assign
> > the result to fruits).
> >
> > Known bugs/limitations:
> >
> > - In the mks_double and mks_single namespaces, time is non-standard in
> > that it is capitalized unlike all the other dimenions.  This is due to
> > my compiler (g++ 3.0.4 on rh) having conflicts with time (which I
> > beleive should be in the std namespace).  Help on solving this would
> > be appreciated.
> >
> > - Many more dimensions could be predefined in the standard system
> > (basically SI).  However, I'd prefer not to define every possible unit
> > (like SIunits), particularlly those that are not frequently used
> > (e.g., furlong) and/or those which can be easily constructed by the
> > user (e.g., meters per second).
> >
> > - Headers for other internal numeric representations (e.g., mks_int
> > ???) could be included.
> >
> > - Other systems (quantum, natural, planetary, ...) could be included.
> >
> > - The system tag classes (e.g., mks_tag, which provides for
> > identifying which system of units is being used and labeling the
> > dimension of quantities) could be made more intelligent.  For example,
> > SIUnits allows users to set the default unit that they'd like a
> > quantity with a certain dimension to be displayed as.  Since one can
> > simply divide by whatever unit they want their result in, I don't see
> > much point.  However, if someone wanted this, they should be able to
> > add such features by replacing the sytem tag class class without touching
> > the rest.
> >
> > Bugfixes, improvements, encouragment, and other feedback would be welcome.
> >
> >
> >
> >
> >
> >
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