Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array?

memnoch has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by friedo (Prior) on Nov 29, 2007 at 21:37 UTC
You can create an ordered hash with Tie::IxHash. Or you can filter duplicates using List::MoreUtils's `uniq` function. (Which basically just uses a hash to do it anyway.) But I think perhaps you're making the problem more complicated than it needs to be. If you describe in more detail what it is you're trying to accomplish, we might be able to offer better solutions.	[reply] [d/l]
Re^2: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by memnoch (Scribe) on Nov 29, 2007 at 22:16 UTC
Thank you friedo! Actually, I just realized that I could do something like: `my $test; unless (exists($hash{$test})) { $hash{$test} = localtime; # For sorting later on }` [download] Then I can do: `sort keys(%hash)` to get the keys in the inserted order.....I'll have to test it later. memnoch *Gloria in Excelsis Deo!*	[reply] [d/l] [select]
Re^3: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by kyle (Abbot) on Nov 29, 2007 at 22:35 UTC
I'd suggest using a counter variable rather than localtime (did you mean time?). `my $count = 0; my $test; unless ( exists $hash{$test} ) { $hash{$test} = $count++; }` [download] This way, you can be sure you don't have duplicate values in the hash, even if you insert two elements at the same second. To do the sorting, you'd need to do this: `sort { $hash{$a} <=> $hash{$b} } keys %hash;` [download]	[reply] [d/l] [select]
Re^4: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by memnoch (Scribe) on Nov 29, 2007 at 23:20 UTC
Re: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by Skeeve (Parson) on Nov 29, 2007 at 21:58 UTC
If you don't want to use a tied hash, you can use an array and a hash. The hash to see whether or not a value has been seen and the array to store the values in order. `push(@array, $value) unless $seen{$value}++` [download] `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]
Re^2: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by memnoch (Scribe) on Nov 30, 2007 at 14:25 UTC
Thanks Skeeve! I tried your code and see that it works, but I don't understand how the `unless $seen{$value}++` works with the autoincrement. Is there an explanation you could point me to? memnoch UPDATE: Okay, I understand it now....I didn't realize that the autoincrement was assigning a value to the hash key that was incremented each time the code runs into the same key. That's very clever! I'm all set. Thank you! *Gloria in Excelsis Deo!*	[reply] [d/l]
Re: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by traveler (Parson) on Nov 30, 2007 at 00:08 UTC
Another way to look at this is that you want a shuffled version of some list. Take (1..7) for example. With Algorithm::Numerical::Shuffle you can do that easily: `@array = shuffle(1..7);` [download] The idea of shuffling an array has been discussed before (and other places, too). HTH, --traveler	[reply] [d/l]
Re: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by Fletch (Bishop) on Nov 29, 2007 at 21:37 UTC
Use Tie::IxHash to maintain insertion order? The cake is a lie. The cake is a lie. The cake is a lie.	[reply]
Re^2: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by memnoch (Scribe) on Nov 30, 2007 at 14:22 UTC
Thanks Fletch! memnoch *Gloria in Excelsis Deo!*	[reply]
Re: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by dragonchild (Archbishop) on Nov 30, 2007 at 04:23 UTC
List::MoreUtils uniq() preserves order. 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^2: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by mreece (Friar) on Nov 30, 2007 at 04:35 UTC
curiously, (the pure-perl version of) `List::MoreUtils::uniq` uses `map { $h{$_}++ == 0 ? $_ : () } @_;` [download] rather than `grep { !$h{$_}++ } @_;` [download] i wonder, a simple preference or are there interesting micro-optimizations in the map verison?	[reply] [d/l] [select]
Re^3: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by dragonchild (Archbishop) on Nov 30, 2007 at 13:36 UTC
I have no idea. If I were to guess, I would say that it probably has to do with a bug report that was received for 5.6.0 on some random OS we've never heard of. Lack of comments make this unclear. 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: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by mreece (Friar) on Nov 30, 2007 at 02:26 UTC
if i understand correctly, you can do it with an intermediate hash and grep. `my %seen; my @nodupes = grep { not $seen{$_}++ } @mayhavedupes;` [download] as for whether you consider grep "having to loop" or not, well, it's a lot less loopy than sorting keys...	[reply] [d/l]
Re: Is there an easy way to assign guaranteed unique values to a simple array without looping through whole array? by aquarium (Curate) on Nov 30, 2007 at 00:10 UTC
there's also a pseudohash in perl...when a particular condition is met (i forget what this is) then the array can be treated as either an array or hash as needed. the hardest line to type correctly is: stty erase ^H	[reply]


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