Re: [boost] Boost Units library preview

From: Andy Little (andy_at_[hidden])
Date: 2006-08-24 10:17:13

"Matthias Troyer" <troyer_at_[hidden]> wrote in message
news:E76A322A-1D3B-4B5C-88A0-2B52FD2387EE_at_itp.phys.ethz.ch...

<...>

> Why not just use a ublas vector or MTL vector with a quan quantity?
> As i mentioned before I see no reason for reinventing the wheel. I
> still have not seen your reason for having your own vector classes.

My use cases for vectors are limited to vectors representing 2 dimensional and 3
dimensional space. I find it convenient to represent a vector in 3 dimensions as
a container with 3 elements representing the direction and magnitude projected
onto the x, y, z axes.  I will certainly look into UBLAS, but my initial
impression is that it is quite heavyweight for this task. Though I havent looked
at MTL, I would guess that it is even more complex than UBLAS. I will look at
MTL2, but so far I have been unable to locate any information on MTL4.

For matrices my tests have been limited to homogeneous transformation matrices.
In this case the matrix elements for a *simple/obvious* implementation of a
matrix for a physical quantity are comprised of various types, comprising of the
quantity type, the reciprocal of the quantity and numeric types. It may be
possible to somehow 'tag' a numeric matrix  as a quantity matrix, but I havent
invetigated that.

I havent looked into other use cases for linear algebra in association with Quan
however. It may be that in the general case ( for large matrices) that it is
impractical ( IOW the costs outweigh any possible benefits) to use non-numeric
types as the elements, but that remains to be investigated.

regards
Andy Little