NAME

Data::Postponed::Once - Delayed evaluation expressions are "collapsed" once observed

SYNOPSIS

Example using postpone_once()

 use Data::Postponed 'postpone_once';
 
 %functions = ( foobar => 'foo' );
 
 $code = "sub " . postpone_once( $functions{foobar} ) . " { return time }";
 $functions{foobar} = "baz";
 
 # Reflects the new name of 'bar' instead of 'foo'. $code isn't
 # overloaded anymore.
 print $code;
 
 # The change to $functions{foobar} is no longer reflected in $code
 $functions{foobar} = "quux";
 print $code;

Example using the OO

 use Data::Postponed;
 
 %functions = ( foobar => 'foo' );
 
 $code = "sub " . Data::Postponed::Once->new( $functions{foobar} ) . " { return time }";
 $functions{foobar} = "baz";
 
 # Reflects the new name of 'bar' instead of 'foo';
 print $code;
 
 # The change to $functions{foobar} is no longer reflected in $code
 $functions{foobar} = "quux";
 print $code;

DESCRIPTION

The value of expressions that have had postpone called on them are in flux until finalized. Once finalized, they are no longer overloaded.

If you want to also prevent changes to input variables because you don't want to accidentally think you're reaching back in time when you're not, use Data::Postponed::OnceOnly.

METHODS

Data::Postponed::Once->new( EXPR )

Returns a new overloaded object bound to whatever was passed in as the EXPR.

"", 0+, bool

Each of these methods are overridden from Data::Postponed. If you wished to only finalize strings, you might just copy the "" and new methods to your own subclass of Data::Postponed.

SEE ALSO

Data::Postponed, Data::Postponed::OnceOnly, Data::Postponed::Forever, overload

This is inspired by what I originally thought Quantum::Superpositions did. Here, the idea is that a value's actual value is in flux until it is examined hard enough and then is a real value.

The companion module Data::Postponed::OnceOnly is used in B::Deobfuscate to turn a two pass algorithm into a single pass. I would have had to do a complete run to get a final symbol table and then run it again to actually use the symbol table. This module allows me to change my mind about the values I've returned.

AUTHOR

Joshua ben Jore, <jjore@cpan.org>

BUGS

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

ACKNOWLEDGEMENTS

Corion of perlmonks.org

COPYRIGHT & LICENSE

Copyright 2005 Joshua ben Jore, All Rights Reserved.

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