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Postings from September 2000
Bart Lateur wrote:
> Hmm... the problem is, I think, that array references and ordinary
> scalars are both scalars.
>
That's true, but they're scalars with different interfaces. In particular,
an array ref can be dereferenced and provides an array in doing so. If an
index can do this, then it's a multidimensional index. Of course, this isn't
how it would actually be handled internally, since it's inefficient, but
this is how its language interface would look.
> What would be the difference between
>
> $a[2]
>
> and
>
> $a[[2]]
>
> anyway? Aren't these just the same?
>
Nearly! From the RFC:
<quote>
When a listref is used to index a list of lists, the returned list reference
is automatically dereferenced:
my @array( [0,1], [1,2]);
my @a = @array[[0]]; # Returns (0,1), _not_ [0,1]
</quote>
Indexing with an integer doesn't have this feature. I considered proposing
adding it (so that all list context assignments dereference the rvalue if
it's a list ref), but I think it would lead to too many incompatibilities
with P5.
> If so, why not grab back into the old box, and get the syntax for
> "multidimensional hashes" in perl4?
>
> single dimension: $hash{$item}
>
> 2 dimensions: $hash{$item1, $item2}
>
> Note that because of the '$' prefix, this cannot be confused with a
> narray slice:
>
> hash slice, not multidimensionanl hash: @hash {$item1, îtem2}
>
> So, the similar syntax for ordinary arrays would then be:
>
> $array[2, 3]
>
> not $array[[2, 2]]
>
> Please feel free to corrct me if I'm wrong.
>
The difficulty with this is that it's not clear how to specify a
multidimensional slice. An index is either multidimensional, *or* a slice,
but not *both*.
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