Re^3: multiple values for one key in hash

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Re^4: multiple values for one key in hash by dragonchild (Archbishop) on May 12, 2008 at 23:04 UTC
It doesn't work if there was an undef explicitly assigned to the value before. A lot of people get tripped up by this because they just assign undef to something they don't use anymore instead of deleting the key. My criteria for good software: Does it work? Can someone else come in, make a change, and be reasonably certain no bugs were introduced?	[reply]
Re^5: multiple values for one key in hash by Fletch (Bishop) on May 13, 2008 at 01:55 UTC
How would autovivification know that the undef in lvalue context it's autovivifying wasn't the original undef? `$ perl -MYAML::Syck -le '$h{bar}=1;$h{bar}=undef;push @{$h{bar}}, qw/a + b c/;print Dump( \%h )' --- bar: - a - b - c` [download] The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l]
Re^6: multiple values for one key in hash by moritz (Cardinal) on May 13, 2008 at 14:51 UTC
How would autovivification know that the undef in lvalue context it's autovivifying wasn't the original undef? By using a proxy object that acts as undef. Note that you need a reference for autovivification anyway because `push @{...}` has to modify something that is stored in place of `...` anyway. I don't know if Perl 5 does it that way, but I think kp6 does.	[reply] [d/l] [select]
Re^6: multiple values for one key in hash by dragonchild (Archbishop) on May 13, 2008 at 14:12 UTC
huh. My understanding was always that an exists check was done in the background (reflecting my experience with the tied madness that is DBM::Deep), but I've never felt curious enough to explore more deeply. My criteria for good software: Does it work? Can someone else come in, make a change, and be reasonably certain no bugs were introduced?	[reply]