Re: [boost] Interest in dimension/unit-checking library?

From: Deane Yang (deane_yang_at_[hidden])
Date: 2005-10-20 13:35:59

Phil Richards wrote:
> 
> If you change your basis set for dimensional analysis, then length
> may not be a basis dimension in this new basis set.  This different
> new (derived) definition of "length" dimensionality has to exist in
> a different namespace to SI length.  And it *can't* interoperate
> with it particularly easily - you would have to specify the
> transformation of each basis dimension from one family to the other.
> 

I have no idea what all this means. Why would I change my "basis set" (I 
assume this means a base collection of dimensions) if I want to use SI 
dimensions?

Why should it matter to you that someone else outside of physics might 
use the library with a completely set of dimensions that are completely 
disjoint from the dimensions you use? I don't understand why that causes 
any problems for you, especially if the library is kind enough to 
provide a layer that predefines the basic physical dimensions and 
corresponding SI units for you. And why should it matter to you if the 
library also allows me to use it without any predefined physical 
dimensions and SI units?

Are you objecting to using an mpl map, because you think it'll 
substantially increase the compilation time? If that turns out to be 
true, I think you do have a case. Then I think we need two completely 
separate libraries, one designed specifically for standard physical 
dimensions and one for user-defined dimensions only.

>>  I am strongly in favor of the former, I have also never understood why
>>  the latter couldn't be built using the former anyway, so the library 
>>  could have two layers to it. The physicists could ignore the lower layer 
>>  completely, and I could ignore the upper one.
> 
> Ok, give a few examples of different basis sets that may be wanted :-)
> The best thing to drive this forward are real use-cases for the library.
> Without them, we'll just go round in circles again.
> 

In mathematical finance, the only essential dimensions are time and 
dimensions derived from time. Why do I want a library that lugs around 
all the other physical dimensions, too?

A general dimension/units library is, I think safe to say, useful 
anywhere one is doing mathematical computations in a practical setting. 
Virtually any practical mathematical calculation uses well-defined 
dimensions and units, and such a library would help guard against 
incorrect formulas. But I don't have specific examples (my experience is 
just as limited as yours); I'll have to let others, if any, speak up.

And, please, if I'm the only one expressing these extreme views, you're 
all welcome to ignore and dismiss me. It's clear that a pure physical 
dimensions library is still extremely useful for a lot of people. I hope 
that one of you (Phil, Matt, Andy) will find a way to submit something 
to boost, even if I don't like it at all.