Vectors and matrices

[JC]

I do a lot of linear work with economic models in D at work. For this reason I 
created small matrix and vector package that makes use of the ATLAS library. 
Most of the time I don't know the sizes of the matrices and vectors that I am 
working with until runtime. Because of this and to keep the memory contiguous, 
the backend of my package is implemented as a dynamic single dimensional array.

Because of this and the fact that static arrays cannot exceed 16Mb (according to 
the D1 docs), I would suggest just working with opIndex(i,j) instead of the 
arrays themselves.

Just my 2 cents,
JC

Lars Kyllingstad wrote:
> I am writing a D library based some of the stuff in SLATEC, and I've 
> come to a point where I need to decide on a way to manipulate vectors 
> and matrices. To that end, I have some ideas and questions I would like 
> comments on from the community.
> 
> Ideally, I want to restrict the user as little as possible, so I'm 
> writing heavily templated code in which one can use both library-defined 
> vector/matrix types and built-in arrays (both static and dynamic). My 
> reasons for this are:
> 
>    a) Different problems may benefit from different types. Sparse 
> matrices, dense matrices, triangular matrices, etc. can all be 
> represented differently based on efficiency and/or memory requirements.
> 
>    b) I hope that, at some point, my library will be of such a quality 
> that it may be useful to others, and in that event I will release it. 
> Interoperability with other libraries is therefore a goal for me, and a 
> part of this is to let the user choose other vector/matrix types than 
> the ones provided by me.
> 
>    c) Often, for reasons of both efficiency and simplicity, it is 
> desirable to use arrays directly.
> 
> My first question goes to those among you who do a lot of linear algebra 
> in D: Do you think supporting both library  types and arrays is worth 
> the trouble? Or should I just go with one and be done with it?
> 
> 
> A user-defined matrix type would have opIndex(i,j) defined, and to 
> retrieve elements one would write m[i,j]. However, the syntax for 
> two-dimensional arrays is m[i][j], and this means I have to put a lot of 
> static ifs around my code, in order to check the type every time I 
> access a matrix. This leads me to my second question, which is a 
> suggestion for a language change, so I expect a lot of resistance. :)
> 
> Would it be problematic to define m[i,j,...] to be equivalent to 
> m[i][j][...] for built-in arrays, so that arrays and user-defined types 
> could be used interchangeably?
> 
> (And, importantly, are there anyone but me who think they would benefit 
> from this?)
> 
> 
> -Lars