NAME
Tie::Scalar::MarginOfError - Scalars that have margins of error
SYNOPSIS
use Tie::Scalar::MarginOfError;
tie my $val, 'Tie::Scalar::MarginOfError',
{
tolerance => 0.1,
initial_value => 1,
callback => \&some_sub,
};DESCRIPTION
This allows you to have a scalar which has to stay within a certain margin of error. Your code will die (or execute what was passed in via the 'callback' subref) if the scalar's value goes outside this range.
You tie a variable, and give it an initial value and a tolerance. Your code will die (or execute what was given in the callback subref) if the value gets beyond +/- whatever you have set the tolerance to be.
In the SYNOPSIS example, $val will cause your code to execute &some_sub if it gets above 1.1 or below 0.9.
If no callback is defined, then the code will simply croak.
More on the callback
If you do define a callback, then it will receive one argument, which is the Tie::Scalar::MarginOfError object. This means you can get out the initial value, if you wish to reset the variable once it exceeds the margin of error.
See t/Tie-Scalar-MarginOfError.t for that very example.
CAVEATS
Yes, you could use this to monitor the core temperature of your nuclear reactor. But the variable is tied, so it can be considered slower than normal. And if you are depending on the reactor not going critical, I wouldn't be using this code. Or perl, come to think of it.
SEE ALSO
perldoc perltie
THANKS
o Dave Cross, whose talk to Belfast.pm made me write this. Blame him.
o Geert Jan Bex for the subref idea.
o Steve Rushe for looking it over and being my personal ispell.
BUGS
Let me know if you spot one. Or if your core goes critical and wipes out the Mid-West of the US. But I guess I would see that on the news.
AUTHOR
Stray Toaster, <coder@stray-toaster.co.uk>
SHOWING YOUR APPRECIATION
There was a thread on london.pm mailing list about working in a vacumn - that it was a bit depressing to keep writing modules but never get any feedback. So, if you use and like this module then please send me an email and make my day.
All it takes is a few little bytes.
(Leon wrote that, not me!)
COPYRIGHT AND LICENSE
Copyright (C) 2003 by Stray Toaster
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.1 or, at your option, any later version of Perl 5 you may have available.