Mr. Newb has asked for the wisdom of the Perl Monks concerning the following question:

I have a problem that, in my mind, instantly calls for the use of a C-sytle struct. I have an array of some items, a name for that array, and a counting variable. I know that there are quite a few ways to overcome this without struct, such as an array of references to these items, or an array with the first two elements as the scalars I need, but these methods seem a bit contrived and awkward. Is there a way to do something like this: 
struct thing
{
my $counting_variable;
my $name;
my @list_of_stuff;
};

[download]
-Bewildered c++ user

Replies are listed 'Best First'.
Re: C-Style Struct?
by BrowserUk (Patriarch) on Aug 08, 2012 at 13:48 UTC

    How about: 

    my %thing = ( name => 'thing', count => 0, list => [] );

++$thing{ count };
print $thing{ name };
print $thing{ list }[ 123 ];

    [download]
    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

    The start of some sanity?
[reply]
[d/l]
      $thing{y}="shock";
[reply]
Re: C-Style Struct?
by Anonymous Monk on Aug 08, 2012 at 13:47 UTC
[reply]
Re: C-Style Struct?
by xiaoyafeng (Deacon) on Aug 08, 2012 at 14:02 UTC
    In general, You don't need to create C-style struct in perl in favor of a hash. But There is indeed several ways to do this, below is one of those: 
    package C_struct;

sub new{
           my $self = shift;
                
           return bless  {'counting_number' => shift,
                                'name'            => shift,
                             'stuff_list'      => shift
                          }, $self;
 }
package main;
use Data::Dumper;
my $cc = C_struct->new(123,'bb', [1,2,3]);
my $dd = C_struct->new(234,'cc', [2,3,4]);
print $cc->{name};
print $dd->{name};
print Dumper $dd->{stuff_list};
1;

    [download]
    Always as a alternative, you can searcg modules on CPAN to reach what you want instead of doing it by hand.

    UPDATE

    modify code to be more intuitive.


    I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction

[reply]
[d/l]
      Your code example doesn't allow access by name, so what's the advantage of it?
[reply]

        You could add accessors to the object. Like this:

        sub count {
    my $self = shift;
    return $self->[0] unless @_;
    $self->[0] = shift;
}

# ...

$cc->count(42);
print $cc->count;

        [download]
[reply]
[d/l]
        changed it, Thanks for your reminding.;)


        I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction

[reply]
Re: C-Style Struct?
by influx (Beadle) on Aug 08, 2012 at 18:51 UTC

    I'm not really familiar with C. But does this work like a struct?

    sub struct {
  my ($name, %args) = @_;
  localscope: {
    # we want to mangle the symbol table
    # so set 'no strict refs'
    no strict 'refs';
    foreach my $a (keys %args) {
      *{"${name}::${a}"} = sub {
        my ($class, $val) = @_;
        # val means it needs updating
        if ($val) {
          nowarning: {
            no warnings 'redefine';
            *{"${name}::${a}"} = sub {
              $val;
            };
          } # end nowarning
          return $val;
        }
        return $args{$a}
      };
    }
  } # end localscope
}

# Create a new struct
struct 'Player' => (
  count_var => 0,
  name => 'Zork',
  list_of_stuff => ['a', 'b']
);

print Player->name;
# you can update a value in this "struct", like so
Player->name('Zippy');

    [download]
[reply]
[d/l]

      Thinking about it, Class::Struct as mentioned in the first reply is probably a nicer option. Seems to do the same thing, but better. And it looks like it's included in perl5.16 - nice!

[reply]
Re: C-Style Struct?
by Mr. Newb (Acolyte) on Aug 08, 2012 at 13:57 UTC
    To BrowserUK, I ran your code, the output is just 'thing'. I would expect it to print 123. What does that line ( print $thing{ list }[123]) do?
[reply]
[d/l]
[reply]
        My self has few answers, that's why I come here. How would I iterate through the array $thing{list}? ie, what would I write for a foreach loop?
[reply]
[d/l]
[select]

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