From: Andre Wobst <wobsta@us...>  20040802 05:47:09

Hi, On 01.08.04, Magnus Lie Hetland wrote: > > One structually missing thing is the "redefinition" of an equation, > > but this should not be hard to add it to the solver. > > No  and in a pinch, you could basically just build a new solver with > one equation redefined. I thought about that as well before, but there seems to be a problem: If you create several solver instances (which is trivial, of course), you can't store the solver results in the scalars itself. You would loose to know, whether a scalar is a constant or it got set by another solver (and should be overwritten?). We can find some way out of this problem, but it might be quite obscure to the user ... Beside that there are quite some other things to be discussed. Just a few which come into my mind immediately: In MetaPost you can define equations, which overdetermine the problem. You can do so by nonescalar equations and I think it's a bad idea to do so, but this might be discussed with people, who are used to the MetaPost equation solver. I'm not sure whether this is a often used feature and whether we should spend time on that at all. Currently the integration in PyX is not thought about. We have at least to think about the interfaces to the path stuff, the transformations and the PyX lengths. And we might think about the basic functionality. Currently I've tried to implement some schoollike vector algebra. For example we do have vectors and we can do scalar products between vectors. Multiplying a vector by another vector will lead to a scalar product. One could also think about introducing dual vectors, so that multiplying a dual vector by a vector will be a scalar product, but multiplying a vector by a dual vector will be a dyadic product and result in a matrix. While there would be *some* people how would like that (I think, I would join that portion), it might be inappropriate to our goals using the system for geometrical operations. So, yes, I think we should stick on what we already have (up to introducing a full transformation), but I'm not totally sure. Beside that we'll need to complete the tests and some fancy examples would be great as well ... André  by _ _ _ Dr. André Wobst / \ \ / ) wobsta@..., http://www.wobsta.de/ / _ \ \/\/ / PyX  High quality PostScript figures with Python & TeX (_/ \_)_/\_/ visit http://pyx.sourceforge.net/ 