Gist of the Day: Old SL4A Example!

So I’m on very little sleep after a long three days of travel which is not yet done. Nonetheless, the show must go on!
Today I have for you a demo program I wrote for CMI.pm a while back (last July I believe) on how to use Perl with SL4A (Scripting Languages 4 Android). This sample code loads a screen which does one of two things: says “something nice” or exits the program. This program demonstrates how to make an event loop for SL4A, how to load an external XML UI resource for Android, and also uses some very basic functionality of SL4A (TTS speak, in particular).
As I am very tired – three hours of very interrupted sleep – I will not be writing any more than this, but I will, of course show you… Continue reading “Gist of the Day: Old SL4A Example!”

Gist of the Day: Counting Bits

I’m pretty sure there’s a more efficient way of doing this, but here’s what I’ve quickly typed up in 10 minutes sitting in my hotel. It just takes in a number, and then the size (in bits) of the number. It returns the number of bits it counts. I believe there is a very common algorithm called the Hamming algorithm, but as I don’t know that algorithm I’ve kinda worked this up instead.
This post is super short as I have a very busy day ahead of me. I’m going to go ahead and just post the code and call it a day. Sorry for the brief post. Continue reading “Gist of the Day: Counting Bits”

Gist of the Day: C Structs from Binary Files Using Perl

Hi, did ya miss me? I’m blogging from O’Hare today, it’s going to be a busy week for me with lots of air travel. That won’t stop me from polluting the Internet with yet another blog post though, don’t you worry!
One of the things that we sometimes encounter is a binary file created by some C program writing a struct straight to disk. If we want to get any of that data we will need to parse this file, and read that struct. It’s a little tricky, and you kinda have to know a little bit about either the system on which he program was run, or the intentional decisions made by the program about how the file was written. The most important thing you need to know is the endianness of the binary data. Continue reading “Gist of the Day: C Structs from Binary Files Using Perl”

Gist of the Day: Find All Paths for an Undirected Graph

I’ve been doing a lot of stuff lately with data structures and algorithms. This is one that seemed remarkably complicated to me – and still kinda does – when I started. It’s not as trivial as a binary tree mainly because there are far fewer rules. There’s a whole lot of stuff you can do with graphs, and this is by no means an advanced or complicated usage of them. This is as simple a task you can do with a graph.
The task at hand is to find all possible paths between two vertices. Continue reading “Gist of the Day: Find All Paths for an Undirected Graph”

Bonus Post: Links About Process Control in GNU/Linux!

So, I’ve been looking into how process control works in GNU/Linux environments, and I thought I’d share some stuff with you guys since you totally care.

That’s all I have for now. Please use the comments section if you’d like to suggest additional articles.

Gist of the Day: Re-Inventing Hashes… In Perl.

Before you begin the well-deserved flaming, please understand that I do not intend on submitting this to CPAN. This is purely an academic exercise to demonstrate the algorithm (poorly), and to help me practice some stuff. I understand that this isn’t terribly efficient, and I am quite confident that one could do this much faster (and probably has many times over). I wrote this for fun, and for boredom, and I’m posting it because I thought it was cool and because I promised you I’d post stuff.
This algorithm is pretty simple. The premise is that you take a key value of some sort, you hash it using any algorithm, and then you take the mod of that hash value by the capacity of your hash table, and that gives you an index! It’s pretty simple, and even in the implementation I have here I believe it’s not a terrible look-up time.
The basic idea is this: $array_index = hashval($key) % $array_capacity
Continue reading “Gist of the Day: Re-Inventing Hashes… In Perl.”

Gist of the Day: Process Control with fork(), exec(), and kill()

I feel really bad for leaving you all high and dry yesterday… really bad… okay, you’re right, I don’t really feel all that bad.
I have a doosey for you all today though, no doubt about it! One of the most common trends in computers these days is multi-processing. Multiple cores means one program can do more work by spawning extra threads or child processes. I’ve already done a bit of stuff with threading, so here’s a bunch of stuff with forking (tee-hee). Continue reading “Gist of the Day: Process Control with fork(), exec(), and kill()”