Re: Some PDL issues (was Re: Test)

Nathan Torkington wrote:
> > (1) The current
> >
> >    $pdl->slice("0:$n,(0)");
> >
> > syntax sucks.
> 
> Would:
> 
>   $pdl->[0:$n][0][:]
> 
> suffice?  I figure this would translate into something like:
> 
>   $pdl->subscript( 0, $n )
>       ->subscript( 0 )
>       ->subscript( undef, undef )
> 
> That is, you can overload [] on objects but instead of being @{}
> as it currently is (where your overload sub returns an array ref)
> you get to handle the subscript operation yourself.

Some comments:

"->" really sucks as something to routinely type in to a interactive shell
all the time. I hate it.  

$pdl[0:$n][0][:]

would be fine as a syntax

BUT we really want the subscription operation to be fast and efficient -
which means doing it with one subroutine call not 3. This is where the 
$pdl[0:$n,0,:] form wins as you can imaging the subroutine just seeing
"0:$n,0,:" in one arg.

Also another common idiom in PDL is:

$pdl[0:$n,(0),:]

where the () means - lose this dimension of size unity. I.e. make the result
MxN rather than Mx1xN. How would this be handled?


> 
> > (2) We see the need for a multidimensional, packed and typed array.
> >
> > The question is: should such an array type be part of perl6 or should it
> > be left to a module to implement such types?
> 
> I vote module.

I guess having true multidim arrays in the core would lead to a [a,b,c[
slicing syntax.

Karl