Re: Dynamic array allocation and STL equivalents?

[bdbryant@mail.utexas.edu (Bobby D. Bryant)]

On Fri, 11 Feb 2005, brian.b.mcguinness@lmco.com wrote:

> One interesting project would be to create an object class hierarchy to
> implement APL arrays.  In APL, the lengths of an array's dimensions can
> change, e.g. by concatenating new rows or columns onto a matrix, or
> concatenating two matrices, and the number of dimensions can also
> change, e.g. by "laminating" two 12x30 arrays to form a 2x12x30 array.
> In C++, an obvious solution would be to use STL vectors, e.g.:
> 
> class RealArray {
>   private:
>     vector <unsigned long> dimensions;
>     vector <double>        data;
>   public:
>     // define an indexing operator[] to use the dimensions
>     // vector to translate sets of indices into offsets
>     // into the data array
>     ...
> };
> 
> But I don't know how to do this in Ada.

If you can work out the recursive data typing issues, you might be
able to do it by overloading the '&' catenation operator to bind a new
row/column/layer onto an array or matrix.

The indexing would be tricky, but if you want think of an array access
as a sort of function call (send an argument, get a result), you might
be able to kludge together a function to do the work.  Let the
function's first argument be the data structure, and the second a
pointer to an (unconstrained) array type that holds the (variable
length) value of the indices of interest.

I think the concept is sound, if you can get everything past the type
checking, though specifying the indices in a program might be tedious.

-- 
Bobby Bryant
Austin, Texas