[Melbourne-pm] Nested maps returning hash references

[Alfie John]

Also, you could have reduced it down by returning a hashref on the
truth side of the ternary:

  map {
    my $f = $_;
    map {
      $f->can($_) ? { $_ => $f->$_ } : ()
    } qw( label name html )
  } @fields

It's a shame you can't access hidden scopes and you need to create a
temporary variable like $f here. Maybe Perl needs a way of accessing
outer block values e.g.:

  map {
    map {
      $_^->can($_) ? { $_ => $_^->$_ } : ()
    }
  } @fields

The $_^ is $_ but one level higher (e.g. git's HEAD^ vs HEAD). But
since having multiple levels would look ugly (e.g. $_^^^ for 3 levels
out, maybe we also need a postfix operator like $_@ which is an array
containing the all of the $_ values for each level:

  $_@ = ( $_, $_^, $_^^, $_^^^ );

But this wouldn't just be for $_, it would work on all variables. That
way, when you local a variable, you can still access the hidden values
too. Perl already stores their values.

Thoughts?

Alfie

On Wed, Oct 5, 2011 at 7:24 PM, Alfie John <alfiejohn at gmail.com> wrote:
> Sorry... read my email during dinner.
>
> Here is what I did as a test:
>
>  #!/usr/bin/perl;
>
>  use warnings;
>  use strict;
>
>  package Foo;
>
>  use base 'Class::Accessor';
>
>  my @fields = qw{ label name html };
>  Foo->mk_accessors( @fields );
>
>  sub new {
>    my $self = bless {}, $_[0];
>
>    foreach my $field ( @fields ) {
>            $self->$field( $field );
>    }
>
>    return $self;
>  }
>
>  my @foos = map { Foo->new() } 1..3;
>
>  use Data::Dumper; warn Dumper([
>          map {
>                  my $f = $_;
>                  {
>                          map {
>                                  $f->can($_) ? ( $_ => $f->$_() ) : ()
>                          } @fields
>                  }
>          } @foos
>  ]);
>
> It looks essentially the same as what you were running. This should output:
>
> $VAR1 = [
>          {
>            'html' => 'html',
>            'name' => 'name',
>            'label' => 'label'
>          },
>          {
>            'html' => 'html',
>            'name' => 'name',
>            'label' => 'label'
>          },
>          {
>            'html' => 'html',
>            'name' => 'name',
>            'label' => 'label'
>          }
>        ];
>
> Take out the + and you get:
>
> $VAR1 = [
>          'label',
>          'label',
>          'name',
>          'name',
>          'html',
>          'html',
>          'label',
>          'label',
>          'name',
>          'name',
>          'html',
>          'html',
>          'label',
>          'label',
>          'name',
>          'name',
>          'html',
>          'html'
>        ];
>
> After looking at yours, it looks like the problem was the trailing
> semi colon after the qw[} :)
>
> Alfie
>
> On Wed, Oct 5, 2011 at 5:44 PM, Toby Corkindale
> <toby.corkindale at strategicdata.com.au> wrote:
>>
>> On 05/10/11 17:38, Alfie John wrote:
>>>
>>> Whoops. That qw{} was in my test code.
>>>
>>> I added the + on the block and it worked for me.
>>
>> That is weird; I tried prefixing a + symbol to both the left-hand-curly-braces in the maps (one at a time), to no avail!
>>
>> This is Perl 5.14.1..
>