Re^5: What does my @x= (undef)x7; do?

[BrowserUk]

You do realise that you aren't passing the array into modify()? You're passing a list. And that list is being aliased.

And prior to the mostly pointless, blanket constanisation of the Perl sources, the (incorrect) attribution of a null C pointer to a scalar would not have been spuriously attributed to a "read-only value".

Two mistakes collide here:

1. The lazy definition of an api that takes a list of pre-existing and defined variables as input in order to provide output.
2. The retroactive application of const'ing at the C-level with callous disregard to the affects at the Perl level.

Upshot: p5p have buggered Perl5 in their attempts to 'be correct'.

[betterworld]

You do realise that you aren't passing the array into modify()? You're passing a list. And that list is being aliased.

Yes I do :) It's a list of aliases, just like in the subroutine GetVolumeInformation from the original post.

p5p have buggered Perl5 in their attempts to 'be correct'.

I think this is related to some optimization. Some people like to use $#array = ... because it is faster than explicitly filling the array. However this optimization comes with a cost.

Assigning to the length does not put any SVs into the new elements, and this is why you cannot create references or aliases to them. I thought there was something about this in the documentation, but I cannot find it any more (only a related section in perlguts)

[BrowserUk]

I think this is related to some optimization. Some people like to use $#array = ... because it is faster than explicitly filling the array.

Oh those naughty "some people"; using a defined language feature in the way it was designed.

[AnomalousMonk]

I would be very interested in any comments you might have on the, to me, very puzzling behavior seen when iterating over the aliased  @_ argument list with arrays  @b and  @c in the  modify() function in the reply above. I have only been able to confirm this behavior in the older Perl versions noted therein.

[BrowserUk]

I assume the main point of confusion is the last case where only one of the elements get modified?

[AnomalousMonk]

You assume too little confusion — always a mistake. Why, in the case of the  @b array, would nothing be changed in the aliased  @_ list? Each case more confusing than the other.