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

From: Randy Roberts (rroberts_at_[hidden])
Date: 2000-12-07 17:07:20

--- In boost_at_[hidden], "Randy Roberts" <rroberts_at_r...> wrote:
> Some of us do alot of interfacing with old F77 or newer F90 code.
> An **intrinsic** FORTRAN-order for the actual array class would
> probably
> be more efficient, especially since we would need a raw pointer to
the
> data in contiguous FORTRAN-order.  Therefore, I propose that the
array
> class be templated on a policy parameter dictating the intrinsic
> ordering
> of the data.
> 
> template <int N>
> class C_ordering_policy
> {
>   // I'll have to think about what goes in here.  Sorry!
> };
> 
> template <int N>
> class F77_ordering_policy
> {
>   // I'll have to think about what goes in here.  Sorry!
> };
> 
> template <typename T, int N, class
OrderingPolicy=C_ordering_policy<N>
> >
> class array : private OrderingPolicy
> {
>   // Use the OrderingPolicy to correctly create sub_array<N-1>
> };
> 
> Sorry it's so sketchy, but my attempt at N-dimensional arrays was
> similar
> to the original article, but used std::valarray for the
> representation.
> The different OrderingPolicy's created and manipulated std::gslice's
> that were contained within the array's representation.  I don't
think
> we want to do this here. :-}

The only problem with this, now that I remember my version,
is that my sub_array's had to handle generalized slices of the
original array's data.  That's why I used the std::gslice mechanism.

array<double,2,F77_ordering_policy> a(dims(10)(20));  // ?? dims ??

a[3] would have to create a
   sub_array<double,1,F77_ordering_policy>
that refers to a 20-strided slice of a's data (whereas
C_ordering_policy would have returned a single-strided slice).

What was so clean about Giovanni's original version was that each
sub_array handled a contiguous range of the array's data.  Do we
want to allow that sub_array's manipulate general slices of the
array's data?

Regards,
Randy
--
Randy M. Roberts           |    "His men would follow him anywhere,
rroberts_at_[hidden]          |     but only out of morbid curiosity." 
rsqrd_at_[hidden]             |            -- a performance review     
work: [phone]