Re^2: Explain the code

[olus]

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

%seen will also have the number of occurrences of every element of @a.

[gopalr]

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

[moritz]

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.

[FunkyMonk]

$seen{4} = 3 means that 4 has been seen 3 times.

[olus]

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
        };