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Re^3: Explain the code

by gopalr (Priest)
on Jul 24, 2008 at 13:08 UTC ( #699868=note: print w/ replies, xml ) Need Help??

in reply to Re^2: Explain the code
in thread Explain the code

How? If the array (@a) has duplicate values, hash will eliminate that.

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Re^4: Explain the code
by olus (Curate) on Jul 24, 2008 at 13:12 UTC

    Noticed the ++ in !$seen{$_}++?

    perl -MData::Dumper -e '@a=(1, 2, 1, 2, 3); my @result = grep { !$seen +{$_}++ } @a; print Dumper(\%seen);' $VAR1 = { '1' => 2, '3' => 1, '2' => 2 };
Re^4: Explain the code
by moritz (Cardinal) on Jul 24, 2008 at 13:09 UTC
    The ++ is evaluated for every item in @a, grep only checks its return value and picks (or not picks) the element based on that value.
Re^4: Explain the code
by FunkyMonk (Canon) on Jul 24, 2008 at 13:11 UTC
    $seen{4} = 3 means that 4 has been seen 3 times.

    Unless I state otherwise, all my code runs with strict and warnings

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