Musings

On occasion, I need a script that will updates reports but only when the sources have changed. This is typically creating an XML file from log files or creating a static page for a web site. Here is a function to determine if the sources have changed after the last time the report was created.

I used Data::Dumper a lot but it leaves something to be desired. By adding a function to MyUtils.pm , a simpler interface can be achieved.

In a previous article , I created an empty module for some utilities. Now is the time to populate it...and to develop tests for the subroutines.

From time to time, I add diagnostic messages to be printed by my code so I can track what the program is doing. I often wondered if there was a way to get Perl to conditionally compile these statements and to get it to do so automatically. Here's how:

Although there are many useful utility subroutines in Perl's standard modules, there are some that are missing. I'm going to spend the next few posts describing a few.

Copyright 2012 by Shawn H Corey. Some rights reserved. Licence under CC BY-SA 3.0 Problem: You have a number of sets and you want all the combinations when choosing one element from each set. In mathematics, these combinations are called the Cartesian product . They are also known as cross-products. In the database world, they are sometimes called cross-joins. This article is to show how to create them using Perl's glob function and how to create them in a subroutine.

Copyright 2012 by Shawn H Corey. Some rights reserved. Licence under CC BY-SA 3.0 At first, recursion seems to be magic. Break the problem into smaller tasks, call the same subroutine to process those sub-tasks, and voilà, problem solved. In truth, it's not quite so simple but all recursion has four steps. Master those steps and you can do recursion with ease.