Re: Parsing attributes in one line using map

[davidrw]

Returning more (or less even) elements than provided is very natural for map and very commonly used, especially for generating hashes .. here's two relatively trivial examples:

perl -MData::Dumper -le 'my %cubes = map { $_ => $_**3 } 1..4; print D
+umper \%cubes'
$VAR1 = {
          '1' => '1',
          '2' => '8',
          '3' => '27',
          '4' => '64'
        };

my @users = [ {id=>4324, name=>'blah'}, {id=>1234, name=>'stuff'}, {id
+=>5678, name=>'foo'} ];
my %usersByName = map { $_->{id} => $_ } @users;
my $id = prompt_for_user_id;
my $user = $usersByName{$id};

Also, see map for more examples (including the basic hash creation), and this quote:

Evaluates BLOCK or EXPR in list context, so each element of LIST may produce zero, one, or more elements in the returned value.

[jhourcle]

Returning more (or less even) elements than provided is very natural for map and very commonly used, especially for generating hashes ..

For those not familiar with returning less -- use an empty list (). To build on davidrw's example:

perl -MData::Dumper -le 'my %oddcubes = map { $_%2 ? ($_ => $_**3) : (
+) } 1..9; print Dumper \%oddcubes'
$VAR1 = {
          '1' => 1,
          '3' => 27,
          '7' => 343,
          '9' => 729,
          '5' => 125
        };