On 29/04/2011 10:27, Uri Guttman wrote:
"RD" == Rob Dixon<rob.di...@gmx.com> writes:
RD> On 29/04/2011 09:15, Brian Fraser wrote:
>> On Fri, Apr 29, 2011 at 5:02 AM, Uri Guttman<u...@stemsystems.com>
wrote:
>>>
>>> so you can streamline yours with a slice:
>>>
>>> my $status = join '', grep defined, @jvalue{ 0 .. 5 } ;
>>
>> This one was on purpose though - The slice might insert new keys into the
>> hash, and I recently spent the good half of an hour debugging just
that..!
RD> Good call Brian. It's not at all obvious that all the elements of a hash
RD> slice will be created if they don't exist :)
and they won't be anyhow. you need have lvalues to autovivify hash (or
array) elements.
perl -le '@x = @y{ qw( a b )}; print keys %y'
%y is empty as you can see.
I meant in the specific case of the grep that was posted. There are no
lvalues there, yet they are autovivified:
perl -le '@x = grep defined, @y{ qw( a b )}; print keys %y'
Rob
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