comatose comatose - 1 year ago 77
Perl Question

perl, removing elements from array in for loop

will the following code always work in perl ?

for loop iterating over @array {
# do something
if ($condition) {
remove current element from @array

Because I know in Java this results in some Exceptions, The above code is working for me for now, but I want to be sure that it will work for all cases in perl. Thanks

Answer Source

Well, it's said in the doc:

If any part of LIST is an array, foreach will get very confused if you add or remove elements within the loop body, for example with splice. So don't do that.

It's a bit better with each:

If you add or delete a hash's elements while iterating over it, entries may be skipped or duplicated--so don't do that. Exception: In the current implementation, it is always safe to delete the item most recently returned by each(), so the following code works properly:

 while (($key, $value) = each %hash) {
    print $key, "\n";
    delete $hash{$key}; # This is safe

But I suppose the best option here would be just using grep:

@some_array = grep {
  # do something with $_
} @some_array;