NAME

Memoize::Attrs - Add memoization with subroutine attributes

SYNOPSIS

    use Memoize::Attrs;

    sub slow_function :MEMOIZE {
        ...
    }
    # slow_function is memoized and faster 

DESCRIPTION

Memoization is a wonderful thing when appropriate. And memoization is a nice optimization trick that may be applied after some thought and experimentation. With the Memoize module, that means to invoke memoize after declaring the subroutine in question.

But that said, memoization looks like a trait and should be added without much fuss. That trivial module makes is possible by annotating subroutine definitions with an attribute MEMOIZE. So that code that looked like

    use Memoize qw(memoize);

    sub slow_function { ... }

    memoize('slow_function');

turns into

    use Memoize::Attrs;

    sub slow_function :MEMOIZE { ... }

which is quite short and happens very early (namely, CHECK time).

This module is not a big deal, but it may help keep the code clean when you have a lot of memoized functions or when you want to add memoization without calling much attention to it.

OPTIONS

    INSTALL => NAME

If NAME does not match /::/, this is installed in the caller package.

    NORMALIZER => CODE | NAME

If NAME does not match /::/, it is resolved in the caller package.

    SCALAR_CACHE
    LIST_CACHE

Just like the options in Memoize module.

SEE ALSO

    Memoize
    Attribute::Handlers

After the release of this module to CPAN, I found

    Attribute::Memoize

There are some subtle differences between the two modules (besides using Memoize x MEMOIZE). Namely,

    * this module resolves non-qualified subnames
      into the caller's package, while 
      Attribute::Memoize requires the use of fully
      qualified names
    * this uses attribute handlers applied at CHECK
      time while the former uses BEGIN-enabled
      handlers. 

BUGS

Documentation needs improvement. And so did tests as well.

We actually install an attribute handler for MEMOIZE at UNIVERSAL -- oh, horror! -- polluting much more than we should. Instead the attribute handler should be installed into the caller of Memoize::Attrs' import subroutine, but it looks like the current exporter modules aren't ready to export subroutines together with their attributes and made their attribute handlers run. I've not digged well enough in this issue and it may be only oversight actually. Time will tell and fixes will come eventually.

The handling of options via the data associated to the attribute MEMOIZE may be faulty yet. But it works

    sub scalar_function :MEMOIZE( LIST_CACHE=>'FAULT' );

for a function which should be called only in scalar context.

    sub slow_function :MEMOIZE( INSTALL => quick_function );

to install a memoized version at quick_function.

Please report bugs via CPAN RT http://rt.cpan.org/NoAuth/Bugs.html?Dist=Memoize-Attrs.

AUTHOR

Adriano Ferreira, <ferreira@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2007 by Adriano R. Ferreira

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

cpanm Memoize::Attrs

perl -MCPAN -e shell
install Memoize::Attrs