Andy Armstrong > Sub-Become > Sub::Become

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NAME ^

Sub::Become - Syntactic sugar to allow a sub to replace itself

VERSION ^

This document describes Sub::Become version 0.01

SYNOPSIS ^

    use Sub::Become;
    
    sub foo {
        my $t = Date->new();
        become {
            return $t;
        }
        return foo();
    }

DESCRIPTION ^

A useful technique in languages like JavaScript is to write a function that replaces its own definition:

    var foo = function() {
        var t = new Date();
        foo = function() {
            return t;
        };
        return foo();
    };

See http://peter.michaux.ca/article/3556 for a complete explanation of the technique.

Sub::Become provides a little syntactic sugar to make this easy in Perl too. See the SYNOPSIS for an example.

INTERFACE ^

become

Replace the current subroutine with the supplied code block:

    sub bar {
        become { 2 }; # return 2 next time
        return 1;     # return 1 first time
    }

If you need to return the value that the new subroutine definition would have returned in the same invocation either have the subroutine recurse:

    sub expensive {
        my $thing = some_expensive_calculation();
        become { $thing };
        return expensive();
    }

Or exploit the fact that become returns the code reference for the new definition:

    sub expensive {
        my $thing = some_expensive_calculation();
        return (become { $thing })->();
    }

CONFIGURATION AND ENVIRONMENT ^

Sub::Become requires no configuration files or environment variables.

DEPENDENCIES ^

None.

INCOMPATIBILITIES ^

None reported.

BUGS AND LIMITATIONS ^

No bugs have been reported.

Please report any bugs or feature requests to bug-sub-become@rt.cpan.org, or through the web interface at http://rt.cpan.org.

AUTHOR ^

Andy Armstrong <andy.armstrong@messagesystems.com>

LICENCE AND COPYRIGHT ^

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

Copyright (c) 2008, Message Systems, Inc. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the
      distribution.
    * Neither the name Message Systems, Inc. nor the names of its
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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