February, 2013

Tech talk: Bloom Filters

Each Thursday at work my team and I do a 45 minute to an hour discussion on any technical subject that we find interesting. We call these Thursday get togethers tech talks and I think they are awesome. We’ve been doing them for years and I’m hoping to start reposting our subjects and a blurb about our discussions each week after they happen.

This week’s tech talk was about bloom filters. A bloom filter is a memory efficient bit vector that contains multiple hashes of your data. It is a probabilistic data structure. The idea is that it can definitively tell you if a piece of data does NOT exist, but it can’t always tell you with certainty that data DOES exist. For more info check out this interactive bloom filter tutorial.

The reason bloom filters are useful is because it is faster and cheaper to transmit a compressed … Read more

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Event emitters with success and fail methods for node.js

When it comes to node.js you hear a lot of hype, good and bad, so I’ve finally decided to take the plunge and investigate for myself what the fuss is about. So far it’s been interesting.

I’m not really building anything in particular right now, I’m just playing with different tech stacks to see how things are done. One of the things that I found I liked, while experimenting with node modules, is the syntax success and fail for callback registration. Something like this:

      .success(function() { })
      .fail(function() { });

Using this kind of syntax I wanted to have a basic user authentication forwarder that I could wrap route calls in such that only logged in users could call the route. Non logged in users would automatically be forwarded to a twitter oauth route for auto login (done using everyauth).

The first step was to create a custom … Read more

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Building a custom lexer

As a software engineer I spend all day (hopefully) writing code. I love code and I love that there are languages that help me solve problems and create solutions. But as an engineer I always want to know more about the tools I work with so I recently picked up “Language Implementation Patterns” by Terence Parr and decided I was going to learn how to build a language. After reading through most of the book and working on examples for about 5 weeks I ended up building an interpreted toy general purpose language that has features like:

  • type inference
  • partial functions
  • static typing
  • classes
  • first class methods

The language I wrote is by no means production level. It’s a toy, and it can do toy things. It can’t do IO, it can’t talk to the OS, it doesn’t do GC, but it does evaluate expressions, call methods, basic … Read more

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Thread Synchronization With Aspects

This article was originally published at tech.blinemedical.com

Aspect-oriented programming is an interesting way to decouple common method level logic into localized methods that can be applied on build. For C#, PostSharp is a great tool that does the heavy lifting of the MSIL rewrites to inject itself in and around your methods based on method tagging with attributes. PostSharp’s offerings are split up into free aspects and pro aspects so it makes diving into aspect-oriented programming easy since you can get a lot done with their free offerings.

One of their free aspects, the method interception aspect, lets you control how a method gets invoked. Using this capability, my general idea was to expose some sort of lock and wrap the method invocation automatically in lock statement using a shared object. This way, we can manage thread synchronization using aspects.

Managing thread synchronization with aspects isn’t a new idea: … Read more

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