After writing this code, I realized many people may have just not realized this is possible, so I think posting it here would make people think more about it.

I was writing a simple script wich would receive a attr=value,attr2=value2 string and automatically I wrote:

my %attrs = map { split /=/ } split /,/, $attr;

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Well, the trick is that map doesn't have to return the same number of elements of the list it receives. If you returns a list inside a map, the resulting list will have more elements than the input list.

This sounds very intuitive to me, but maybe it's not for others...

daniel

Replies are listed 'Best First'.
Re: Parsing attributes in one line using map
by izut (Chaplain) on Sep 25, 2006 at 10:34 UTC
    You can do this (borrowed from 'Perl for System Administrators'): 
    my %attrs = split /=|,/, $attr;

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    Igor 'izut' Sutton
    your code, your rules.

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Re: Parsing attributes in one line using map
by davidrw (Prior) on Sep 25, 2006 at 12:44 UTC
    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};

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    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.
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      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
        };

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Re: Parsing attributes in one line using map
by jdporter (Paladin) on Sep 25, 2006 at 14:53 UTC 

    split /=/

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    should be 
    split /=/, $_, 2

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    But what if any of the values contains ',' or '='? 

    my %attrs = $attr =~ /([^=,]+)=(.*?)(?:(?=,[^=,]+=)|$)/g;

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    We're building the house of the future together.
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