Monthly Archives: March 2012

code golf

I came across a new (to me) game yesterday – Code Golf.

The game involves coming up with an algorithm to solve a programming problem, and trying to condense the code for the algorithm into the smallest number of bytes possible.

The first one I tried was this. It was a fascinating problem, and took me a day of musing on it (in the back of my head as I did other things) before I had a solid solution.

After writing the solution, which took 1380 bytes, it was time to start “golfing” it.

At first, I thought I’d try my compressor on it. This shrank it to 825 bytes, but after compression, it couldn’t be worked with anymore, so I thought I’d try compressing it manually.

This resource was fascinating, and gave me a load of pointers.

There were a few small points I came up with myself while working on it:

I prefer to use “\n” instead of “;” for command endings, as it makes code more readable. (the game is about shrinking the code, not obfuscating it)

A saving can be had by combining nested loops:

// before
for(i=5;i--;)for(j=5;j--;)M[i][j]=0
// after
for(i=25;i--;)M[0|i/5][j%5]=0

If you need to push into an array on multiple lines, make a shortcut for the push method:

// before (example)
a=[]
cond1()&&a.push(1)
cond2()&&a.push(2)
cond3()&&a.push(3)
cond4()&&a.push(4)
// after
a=[]
P=a.push
cond1()&&P(1)
cond2()&&P(2)
cond3()&&P(3)
cond4()&&P(4)

If possible, find a maths way of identifying interesting points, instead of comparisons.

// before
if((x==4&&y==4&&z==3)||(x==4&&y==3&&z==4)||(x==3&&y==4&&z==4))dosomething()
// after
if(x*y*z==48)dosomething()

I think this game is really interesting, and it will sharpen my own skills as a programmer, as it taxes the mind not only to find the solution to a problem, but also to express that solution as concisely as possible.

In the end, I was able to solve the problem in 668 characters – that’s 142 characters less than my compressor was able to manage.

musical intervals trainer, web version

last weekend, I wrote an intervals trainer app for practicing recognising intervals.

I want other people to use it, but haven’t got a Google development account yet so can’t upload an app.

So, today, I improved the app and made a web-accessible version.

try it out!

it’s designed to move up from very simple intervals (major/minor 2nd intervals, with only natural notes) to more difficult intervals (diminished/augmented, with double sharps and flats), but it’s also designed to only get more difficult at a rate that /you/ can manage.

to do this, the app uses a “levels” system, where each level has one more extra type of interval or note type, and you are tested on them. over 50% of the time, the question will be from the level you’re on, and the rest of the time, the question will be randomly chosen from every other level that you have already passed.

get 10 in a row correct, and you go to the next level.

but, get 5 wrong in a row, and you go down a level.

at the moment, there are 24 levels – all the way up to augmented 8ths – can you get through all the levels?

give it a try!

music theory trainer app

i had an itch to scratch over the weekend, so wrote up a simple app for working on music intervals.

If you have an Android phone, feel free to download this file and give it a try:

MusicTheoryPocketTrainer.apk

Note that this app is not in the market. You need to install it manually. Here are some instructions on how to do that.

Adding a trigger-based plugin to WebME

One of my clients has his own fork of WebME that he keeps current with the SVN version.

He mentioned a collision recently, where a hack he had written into the online store plugin was overwritten by updates.

So, in this post, I’ll demonstrate how to add a plugin that uses a trigger to run some code.

First, we define what needs to be done.

The client wants that when an order in an online store has been processed, an email is sent out to that client.

This immediately points out where the trigger point goes. The processing of orders is done in the file ww.plugins/online-store/verify/process-order.php, so we need to put the trigger in there as well, at the end of the OnlineStore_processOrder() function:

  Core_trigger('after-order-processed', array($order));

What happens at that point is that the CMS will check all plugins to see if there are any that have a trigger of the name “after-order-processed”, and if there are, then that trigger will be fired.

So, next we need to create the plugin. In fact, it’s so easy I’ll just write it straight out. I’m calling this one “DemoPlugin”, so we start by creating the directory /ww.plugins/demo-plugin”, and placing the file plugin.php in it:

<?php
$plugin=array(
  'name' => 'DemoPlugin',
  'triggers'      => array(
    'after-order-processed'=>'DemoPlugin_afterOrderProcessed',
  ),
  'description' => 'Sends an email after an order is processed',
);

function DemoPlugin_afterOrderProcessed($PAGEDATA, $order) {
  mail('kae.verens@gmail.com', 'subject line', print_r($order, true));
}

Simple!

Now, in order to do this, I edited one file which is part of the “official” WebME package, to add the trigger. If you find you need to do this, please contact me and tell me what you’re trying to do, and what you edited, so I can add it to the SVN version and not break your code in future releases.