NAME
Tie::Coupler - Tie based implementation of coupled scalars
SYNOPSIS
use Tie::Coupler;
my $options = { fconvert => \&double,
rconvert => \&half,
init => 1,
};
my $impl = new Tie::Coupler($var, $coupled, $options);
$var = 2;
print "$var, $coupled\n"; ## Would print: 2, 4
$coupled = 6;
print "$var, $coupled\n"; ## Would print: 3, 6
$impl->fconvert(\&triple);
$var = 5;
print "$var, $coupled\n"; ## Would print: 5, 15
$impl->decouple(); ## The two scalars are now independent
## of each other now
sub double { my ($val) = @_; $val * 2; }
sub triple { my ($val) = @_; $val * 3; }
sub half { my ($val) = @_; int($val / 2); }
DESCRIPTION
`Tie::Coupler' provides a mechanism by which you can couple two scalars.
That is the value of the coupled scalar would determined by the value of
the scalar to which it is coupled. The code referenced by the options
fconvert and rconvert determine the relation between the two scalars.
The complexity/functionality of the coupling is only limited by your
sense of imagination. The simplest form of coupling is a one to one
coupling wherein the conversion functions are undefined. In this form of
coupling the two scalars would have the same value at any point of time.
CONSTRUCTOR
new (VAR, COUPLED [, OPTIONS ])
Creates a new coupling. It takes two mandatory parameters, the first
one VAR is the scalar to be coupled and second parameter COUPLED is
the scalar to which VAR is coupled. OPTIONS is an optional parameter
specifying the behaviour of the coupling. The options are passed to
the constructor as a hash reference. The following are the valid
keys and their corresponding effect on the coupling:
Option Type Default
------- ---- -------
fconvert Code Reference None
rconvert Code Reference None
init Boolean 0
The constructor returns the implementation object that gives the
coupled scalar the desired functionality. This implementation object
can be used to alter the behaviour of the coupling by calling the
appropriate methods.
After the constructor successfully creats the coupling, the two
scalars can be used as normal scalar variables. But the magical
spell (coupling) cast on the scalars would mean that at any point
the value held by the scalars would be based on:
1. The value of the other scalar
2. The characteristics of coupling as specified by the
conversion routines (fconvert & rconvert)
OPTIONS
fconvert => CODEREF
This options defined the callback to be invoked whenever the COUPLED
scalar's value changes. The value of the COUPLED scalar is passed as
an implicit parameter to this function. The code reference can be
specified in one of the following ways:
1. As a code reference - \&function 2. As an anonymous function -
sub { function(); } 3. As an array reference - [ $obj, $method,
@params ]
The value returned by the function referred by fconvert would be
used to determine the relation between the two scalars in the
forward direction.
rconvert => CODEREF
Same as fconvert, but determines the relation between the two
scalars in the reverse direction.
init => BOOLEAN
If this option is TRUE, then the value of the coupled scalars would
be initialized based on the conversion functions.
METHODS
$impl->fconvert (CODEREF)
Utility method to set the value of the fconvert function.
$impl->rconvert (CODEREF)
Utility method to set the value of the fconvert function.
$impl->decouple ()
Decouples the scalars, releasing the scalars from the magical spell.
Once decoupled the scalars continue to behave like normal perl
scalars.
LIMITATIONS
The code has not been fully optimized in terms of processing speed and
memory utilization. Every read/write access on a coupled scalar has a
constant overhead. The magnitude of the overhead is determined purely by
the complexity of the conversion routine(s).
KNOWN BUGS
May be lot of them :-), but hopefully none. Bug reports, fixes,
suggestions or feature requests are most welcome.
COPYRIGHT
Copyright (c) 2001-02 Arun Kumar U <u_arunkumar@yahoo.com>
All rights reserved.
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
AUTHOR
Arun Kumar U <u_arunkumar@yahoo.com>, <uarun@cpan.org>
SEE ALSO
perl(1), perltie(1)
=======================
HOW TO INSTALL IT ?
To install this module, cd to the directory that contains this README
file and type the following:
perl Makefile.PL
make
make test
make install
To install this module into a specific directory, do:
perl Makefile.PL PREFIX=/name/of/the/directory
...the rest is the same...
Please also read the perlmodinstall man page, if available.
Share and Enjoy !!
Arun Kumar U
<u_arunkumar@yahoo.com>
<uarun@cpan.org>
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