> while (my $key = delete_first %hash)
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.
The only difficulty might be efficiency consideration:
- 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;
}
}
°) 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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