On Aug 24, 2006, at 11:17 PM, Andy Little wrote:
"Matthias Troyer" <troyer@itp.phys.ethz.ch> wrote in message news:E76A322A-1D3B-4B5C-88A0-2B52FD2387EE@itp.phys.ethz.ch...
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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 that purpose the Blitz++ TinyVector class seems ideal, and I think that MTL4 will have something similar.
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.
Just use a quantity as value type? What's the problem with 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.
Why? What should be the problem? Your quantity is just a number, and the rest is compile time type information? Or is a quantity heavier than just a floating point number? Matthias