Re: (bbfu) (eq instead) Re3: Appending an array

push @data, $response unless grep { $_ eq $response } @data;
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Please advise, I understand now that the push function adds to end of list but why is the grep on the response needed?
Basically what is the grep { $_ eq $response } @data part doing??

Comment on Re: (bbfu) (eq instead) Re3: Appending an array Select or Download Code

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Finding answers in perl (How to fish) by boo_radley (Parson) on May 31, 2002 at 14:42 UTC
This may be a good time to point out all the wonderful things that perl (including grep) can do for you. Any time you have a question about what a certain function does, you can type `perldoc -f functionname` and get a reasonably detailed explanation.	[reply]
grep in a conditional by ChemBoy (Priest) on May 31, 2002 at 16:37 UTC
What grep does is go through the list and return a sublist of elements that (in this case) are equal to the element you're about to add. That sublist is then evaluated in boolean context by the unless: if the sublist is empty, it evaluates false, and the push takes place; if it's non-empty (which is to say, if `$result` appears in `@data` already), it evaluates true, and the push is stopped. In effect, the `unless grep...` means "unless we've already seen this result": it's there to prevent you from adding duplicates to `@data`. You could filter for it later on, but it'd be a pain, so pre-filtering it makes a lot of sense. If God had meant us to fly, he would never have given us the railroads. --Michael Flanders	[reply]