Re: [boost] [units]

From: Steven Watanabe (steven_at_[hidden])
Date: 2007-03-05 15:32:59

AMDG

Brook Milligan <brook <at> biology.nmsu.edu> writes:

> It seems that the mcs-units library is moving along well.  I have one
> question, though, about scope and whether the following should be
> within the scope of this library or within the scope of another one.
> 
> In building probability and likelihood models, I often encounter the
> issue of transforming from either to their logarithms and vice versa.
> Code would be much simpler and less error-prone if the appropriate
> domain was defined, the natural arithmetic operators were used, and
> the conversions occurred (or could be prevented to catch errors) as
> necessary, but without necessarily requiring explicit bookkeeping to
> distinguish these quantities and their logarithms.
> 
> This suggests a (small) set of types with appropriate conversions,
> much as in the units library.  However, probabilities are of course
> unitless.
> 
> Should this idea be developed as a separate library or does it make
> any sense to fold it into the existing units framework?

It would be better to develop a separate library.
Units supports only linear conversions.  You need
multiplication to yield the same type as the operands
Units usually gives a different type.  The specializations
that you would need to define to make Units do what
you want would require as much code as if you defined
the classes by hand.

> Cheers,
> Brook

In Christ,
Steven Watanabe