Re: exists $foo[7] and delete $foo[7]

[Larry Wall <larry@wall.org>]

Tom Christiansen writes:
: >IIRC, the current documentation says it will be fixed in a future
: >release.
: 
: My copy reads:
: 
:     This surprising autovivification in what does not at first--or
:     even second--glance appear to be an lvalue context may be fixed
:     in a future release.
: 
: This is *not* related to exists().

That's correct, insofar as exists() is an rvalue.

: You have to make all uses of
: the pointer arrow dereference, implicit or explicit, stop autovivifying.
: 
:     $x[$i][$j] += $y[$i][$j] if $z[$i][$j] < 10;
: 
: That will autovivify three things.  Your task, if you choose to
: accept it, it to make it autovivify but two of them.

It shouldn't autovivify on any rvalues.  I only see one lvalue there,
so I only see one ref autovification (plus one array element creation).

: But there are a lot of other border situations to consider.  Here's one:
: 
:     $x[$i][$j] =~ s/foo/bar/;   
: or
:     $x[$i][$j] =~ s/^//;   		# how no-op-py is this *really*?

Those have always been considered lvalues.  Same for tr///.  But not
for m//.

: And then there's this fun one:
: 
:     somefunc( $x[$i][$j] );

That's been considered an honorary lvalue for some time, if I recall.

Larry

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Follow-Ups from:

Larry Wall <larry@wall.org>

References to:

Tom Christiansen <tchrist@chthon.perl.com>

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