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

From: Randy Roberts (rroberts_at_[hidden])
Date: 2000-12-07 16:04:51

--- In boost_at_[hidden], Daryle Walker <darylew_at_m...> wrote:
> on 12/5/00 9:53 AM, Gavin Collings at gcollings_at_s... wrote:
> 
> [SNIP]
> > All of those alls seem to hint at a commonality; better it would
be
> > to support the all element interface through a view: -
> > 
> > 
> > class flattened_array
> > {
> > public:
> > 
> > flattened_array( array * );

[SNIP]

> > // insert clean container interface here.
> > 
> > private:
> > 
> > array * array_;
> > };
> > 
> > class array
> > {
> > // ...
> > 
> > flattened_array flat() { return flattened_array( this ); }
> > };
> 
> Should flattened_array be a friend of array?  If not, then
flattened_array
> has to work by translating array indices.  If it does use indices,
then we
> could offer a FORTRAN-order version along with the normal (C-order)
version.
> FORTRAN-order puts the fastest index first instead of last.

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. :-}

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]