Re: A class template for an N-dimensional generic resizable array

From: mschuerch_at_[hidden]
Date: 2000-12-04 05:54:35

I would very much like a multidimensional array-class in boost. I'm 
one of the ones, which have to use VC. Blitz++ is therefore no 
alternative.

> 
> I think this is part of a very important issue. Should we see an N 
> dimensional array as a container of elements, or as a container of 
N-
> 1 dimensional arrays? It really is both, but which view simplifies 
> what we want to do with it? How do we want to access it? I think I 
> ended up privileging the former view, that of a multidimensional 
> array as a container of elements, structured in N dimensions, and I 
> just used class SubArray as a way to get at the elements. I do not 
> treat the various dimensions differently. When I resize the Array, I 
> resize it all, I pass all the N dimensions of the Array to the 
resize 
> member function (naturally some of these can remain the same, and in 
> any case, I preserve the existing elements where possible and 
> desired). I do not see the first dimension as being different, and 
> the result is that in my thinking:
> 

> 1) size() returns the total number of elements in the N dimensional 
> (sub)array, not the number of N-1 dimensional subarrays.
> 2) begin() returns an iterator that allows direct access to the 
first 
> element, not to the first N-1 dimensional array.  
> 3) I wanted to maintain also a flat view of the underlying elements, 
> so that I could apply algorithms and traverse the array 
sequentially, 
> following the order in which the elements are stored in memory. 
>

I also think that a multidimensional array should be a flat container 
with some mapping.

For the special case of N=2 this mapping mode should be compatible 
with e.g. LinPack:
iflat = offset + i*istride + j*jstride

I think this is not possible with the second concept.

Some kind of expression templates would be the sugar of the library.

regards
Martin