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Re^3: What does 'next if $hash{$elem}++;' mean?

by inman (Curate)
on Feb 17, 2006 at 15:51 UTC ( #530980=note: print w/replies, xml ) Need Help??


in reply to Re^2: What does 'next if $hash{$elem}++;' mean?
in thread What does 'next if $hash{$elem}++;' mean?

It isn't necessary to do all of the intermediate processing. You can read a line and check it all at the same time.

The line is used as a hash key. The value is tested before being incremented and the line is added to the array.

my %seen; while (<PROCESSED_FILE>){ push @unique, $_ unless $seen{$_}++; }

This is OK if the hash doesn't grow to big. Using MD5 hashes of lines is an uesful technique.

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[Corion]: GotToBTru: Yeah, I started a quick(ly implemented but slowly running) implementation of a program that would guess the "best" configuration (that is, least amount of changes) from my code, but then found that it stops parsing the source as soon as it ..
[GotToBTru]: sadly, it can't do anything about this
[Corion]: ... encounters sub foo($bar,$baz) {, which is something I like nowadays
[Corion]: GotToBTru: Yeah, that stuff is hard to do away automatically ;)
[GotToBTru]: yeah, you mentioned it could not handle signatures
[Corion]: And so far I like signatures and nobody has yet come up to me and screamed at me for implementing a source filter to handle them even on early Perl versions ;)

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