March 2009 Archives

Create a list of primes “as you go”, considering a number prime if it can’t be divided by any number already considered prime.

However, although my straightforward solution worked on discrete ranges, it couldn’t yield a single prime when called on an infinite range – something I’m completely unused to from other languages, except for some experience with the SERIES library in Common Lisp.

Haskell may be difficult to start out with, but once things start rolling, they roll fast. Yesterday (real world time, these blog entries are staggered) I had started the first lines of HackPorts, but now things are getting close to done for the first version. It’s not that I’ve written much code, but that it was simple to integrate with other people’s code.

As I explore Haskell, I’m discovering that one of its trickiest aspects is not structuring things functionally, but the lazy evaluation. It turns out lazy evaluation comes with both great benefits, and significant difficulties. I’d like to point a few of these out, as they’re becoming clearer to me.

I’ve been reading Real World Haskell now, after having finished the delightful Learn You a Haskell Tutorial. I’m up to chapter 6, about to dive into Typeclasses. In the meantime, I’ve picked a toy project that also has a taste of usefulness: a script to convert the Hackage database into MacPorts Portfiles, respecting inter-package and external library dependencies. I call it HackPorts, of course.

Recently I changed how the content on this site was generated, from using the standalone OS X application RapidWeaver, to the server-side publishing platform Movable Type. During that transition I changed the site’s style to the minimalist default offered by MT, which uses its own CSS for column layout and typography.

Tonight I finally got around to switching the site back to blueprint-css, which I very much prefer. I used the superb application CSSEdit to help me massage Movable Type’s style into something that compatible with Blueprint’s own typography and layout.

I hope the result is pleasing. If anyone sees strange artifacts or display issues, please let me know. I’m aware code examples were being truncated on the right side before, but this should be corrected now. More on Haskell to come soon!

Today I need a wrapper script to drop arguments from a command-line. I instinctively reached for bash, but then thought it would be a good exercise for my infant Haskell knowledge.

Everybody talks about Monads when they mention Haskell, so I got a bit ahead of myself and wanted to see something of what they’re about. No, don’t worry, I’m not aspiring to yet another Monad tutorial. I feel I have a ways to go before I’m ready to craft my own light-saber.

I did read about 10 Monad articles on the Web, and found myself more confused when I came out than when I went in. Today’s exercise took about 5-6 hours of pure frustration, before a kind soul on IRC finally set me straight. It sure is difficult when getting past a single compiler error takes you hours.

Having just begun my descent down the rabbit hole, I thought I’d try journaling about what I discover along the way, so that those who are merely curious can play the part of language voyeur. I’ve always wanted to do that: to see how someone dives into Erlang or O’Caml or Forth – or Haskell. Here’s your chance.

In a recent entry on differences between Haskell and Lisp, one of the Lisp community’s long-time members, Daniel Weinreb, asked about my stated aversion to JVM-based languages for everyday computing (sometimes referred to as “scripting”). Specifically, it was asked in relation to Clojure, and why I hasn’t been immediately taken by that language – despite it’s having so many features I respect and admire.

I wanted to respond to Daniel’s question in a separate blog entry, since this topic has come up so often, it seems, and deserves thought. The JVM is a rich, mature platform, and you get so much for free by designing new languages on top of it. The point of debate is: what are the costs, and are they always worth the asking price?

Someone recently asked what my issue was regarding the JVM, since at the moment it prevents me from falling too much in love with Clojure – a language with the double-benefits of functional programming, and Lisp syntax and macros.

Well, below is my reason. These may not seem like much time in the scheme of things, but psychologically it builds up on me when I have to run a particular script over and over and over again. I’ve already noticed the pain with Groovy.

If you’d like to generate some of these timings for your own system, I have created a Hello, world project on GitHub.

As some one who has enjoyed the Lisp language (in several flavors) for about 15 years now, I wanted to express some of my reactions at recently discovering Haskell, and why it has supplanted Lisp as the apple of my eye. Perhaps it will encourage others to explore this strange, wonderful world, where it looks like some pretty damn cool ideas are starting to peek over the horizon.