Re: proposed addition to perlvar

On Mon, Jun 14, 2010 at 11:22:58AM +0200, demerphq wrote:
> On 14 June 2010 10:46, Abigail <[email protected]> wrote:
> > On Mon, Jun 14, 2010 at 10:04:09AM +0200, demerphq wrote:
> >>
> >> I agree, but I think it would be the place to note that using $#arry
> >> unguarded by an array size assertion may result in a fatal exception.
> >
> > Fatal exception? Could you provide an example of that?
> >
> >    $ perl -wE 'my @x; say $x [$#x]; END {say "Hello"}'
> >    Use of uninitialized value in say at -e line 1.
> >
> >    Hello
> >    $
> 
> My mail was pre-coffee, and i have to admit i thought that fetching -1
> on an empty array was an error. You have a collection of old perls
> right? Was there an older version where fetching -1 on an empty array
> /was/ an error?

I currently don't have anything older than 5.005_04. In which it wasn't
an error. And I do not believe it ever was an error.

> 
> Anyway, I meant this exception, for /setting/ the last element in an array:
> 
> perl -lwe'use strict; my @array; $array[$#array]=1'
> Modification of non-creatable array value attempted, subscript -1 at -e line 1.
> 

Yes, but that's not a feature of $#.

 $ perl -wE 'my @a; $a [@a - 1] = 1'
 Modification of non-creatable array value attempted, subscript -1 at -e line 1.
 $


Nor is it a feature for empty arrays:

 $ perl -wE 'my @a = (1); $a [@a - 3] = 2;'
 Modification of non-creatable array value attempted, subscript -2 at -e line 1.
 $



Abigail