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Showing posts from October, 2007

On the Importance of Purity

The benefits of advanced programmings languages are sometimes difficult to grasp for everyday programmers. The features of such languages and how they relate to industrial software development are sometimes hard to understand, especially since the arguments are couched in terms such as "referential transparency", "totality", "side-effect-free", "monads", "non-determinism", "strong static typing", "algebraic data types", "higher-order functions", "laziness/call-by-need", and so on.

Many of these features are attributed to "pure" languages, but purity is also a nebulous concept. I will explain the importance of a number of these features and how they impact the everyday programmer's life.

The Benefits of Referential Transparency
Referential transparency (RT) is a simple principle with profound consequences. Essentially, RT dictates that functions may access only the parameters they'r…

Reading PDFs on the iPhone the moderately difficult way

Taking a break from my programming language blogging, I thought I'd describe a recent adventure with my new iPhone: reading PDFs. The iPhone can read PDFs, but insists on doing so only when reading the PDF from the network in some way, ie. via the mail client or Safari.

Being the programming language enthusiast I am, I have plenty of papers stored locally on my machine which I'd like to read on the go, and network access is less than desirable for obvious reasons. Unfortunately, Apple disabled the obvious answer to local browsing: using the "file://" URI scheme. Very stupid of them IMO.

Fortunately, I'm an "unscrupulous" person, because I jailbroke my iPhone so I could install third-party apps. So if network access is required to view PDFs in Safari, then I'll just have to access local files over the network! The way that's been done for over 20 years is available on the iPhone: a web server.

Both Apache and LightTPD are available in Installer.app,…