in reply to Re^5: Iterating over hash while deleting elements
in thread Iterating over an hash while removing keys
I don't think a new iterator is the best generic approach.
Because only the loop's body knows if resetting the iterator is appropriate.
for the general case - iterating a hash and occasionally deleting elements in the body, this should always fit
while (my $key = each %hash) { if ( condition($key) ) { delete @hash{ dependent_keys($key) }; keys %hash; } }
The Rule: reset the iterator if and only if other elements are deleted.
This will never end in an endless loop, because the hash will
- either be emptied ²
- or the last "re-iteration" is not interrupted.
- If the $key itself is deleted
=> this should be done outside the if-block to not reset ° - If the $key itself is NOT deleted
=> you might want to avoid processing it again by a checking a %seen hash.
my %seen; while (my $key = each %hash) { next if $seen{$key}++; if ( condition($key) ) { delete @hash{ dependent_keys($key) }; keys %hash; } }
Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery
FootballPerl is like chess, only without the dice
°) not sure how costly resetting is in the end.
²) provided it's a finite structure which isn't refilled simultanously
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Re^7: Iterating over hash while deleting elements (Best Practice)
by Eily (Monsignor) on Feb 07, 2020 at 14:11 UTC | |
by LanX (Saint) on Feb 07, 2020 at 14:23 UTC |