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 / 
Const-0.01
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/ Const

NAME

Const - Facility for creating read-only variables

VERSION

$Id: Const.pm,v 0.1 2008/06/26 22:26:16 dankogai Exp dankogai $

SYNOPSIS

 use Const;
 Const my $sv => $initial_value;
 Const my @av => @values;
 Const my %hv => (key => value, key => value, ...);

 use Const qw/dlock dunlock/;
 # note parentheses and equal
 dlock( my $sv = $initial_value );
 dlock( my $ar = [@values] );
 dlock( my $hr = { key => value, key => value, ... } );
 dunlock $sv;
 dunlock $ar; dunlock \@av;
 dunlock $hr; dunlock \%hv;

DESCRIPTION

Const is a drop-in replacement for Readonly. It has the same functionality as Readonly but istead of using tie, it makes use of SvREADONLY. Readlonly::XS does that but only to scalars while Const recursively makes all scalars in arrays and hashes.

Note that it does not recurse on blessed references for a good reason. Suppose

    package Foo;
    sub new { my $pkg = shift; bless { @_ }, $pkg }
    sub get { $_[0]->{foo} }
    sub set { $_[0]->{foo} = $_[1] };

And:

    Const my $o => Foo->new(foo=>1);

You cannot change $o but you can still use mutators:

    $o = Foo->new(foo => 2); # BOOM!
    $o->set(2);              # OK

If you want to make $o->{foo} immutable, Define Foo::new like:

    sub new {
      my $pkg = shift; 
      Const my $self = { @_ }; 
      bless $self,  $pkg;
   }

Or consider using Moose.

EXPORT

Const by default. dlock and dunlock on demand.

FUNCTIONS

Const

See "SYNOPSIS".

dlock

  dlock($scalar);

Locks $scalar and if $scalar is a reference, recursively locks referents.

dunlock

Does the opposite of dlock.

BENCHMARK

Unlike L <Readonly> which implements immutability via C <tie()>, Const just turns on read -only flag of the scalars so it is faster. Check t/benchmark.pl for details.

Scalar Rate constant Readonly Const literal glob constant 35461/s -- -32% -93% -99% -99% Readonly 52083/s 47% -- -90% -99% -99% Const 526316/s 1384% 911% -- -89% -89% literal 5000000/s 14000% 9500% 850% -- -0% glob 5000000/s 14000% 9500% 850% 0% --

Array w/ 1000 elements

           Rate Readonly    Const  literal     glob
  Readonly 1205/s       --     -49%     -67%     -80%
  Const    2381/s      98%       --     -36%     -60%
  literal  3704/s     207%      56%       --     -37%
  glob     5882/s     388%     147%      59%       --

Hash w/ 1000 key-value pairs.

            Rate Readonly    Const  literal     glob
  Readonly 180/s       --     -35%     -41%     -59%
  Const    277/s      54%       --      -9%     -36%
  literal  305/s      70%      10%       --     -30%
  glob     433/s     141%      56%      42%       --

AUTHOR

Dan Kogai, <dankogai at dan.co.jp>

BUGS

Please report any bugs or feature requests to bug-const at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Const. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc Const

You can also look for information at:

COPYRIGHT & LICENSE

Copyright 2008 Dan Kogai, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.