I am happy to announce the release of Blunt. Blunt converts Haskell expressions between the pointfree and pointful styles. I implemented it as a web service and hosted it on Heroku. Check it out at blunt.herokuapp.com.

I created this service because I don’t always have the pointfree and pointful commands at the ready. Since they take about five minutes to install, querying a web service is much faster. Some people rely on Lambdabot in the Haskell channel on IRC. I don’t usually idle in IRC, so that isn’t too useful to me. Plus I can easily use Blunt on someone else’s computer or even my phone.

Blunt is a simple single-page app, but it uses some cool technology behind the scenes. In particular, it uses WebSockets to avoid the overhead of making an HTTP request for every change to the input. And of course the whole thing is itself written in Haskell. The excellent Haskell on Heroku buildpack makes deploying to Heroku a piece of cake.

I learned some useful packages while developing Blunt. Warp powers the whole thing. I have used it before and it continues to impress. Combining it with WAI WebSockets could not have been easier. I went from a simple HTTP server to a combination HTTP and WebSockets server in only a couple minutes and a few lines of code.

For rendering markup, I went with Lucid. I’ve never used it before and found it extremely nice to work with. If you want to build HTML in Haskell, use Lucid. Seriously, it’s that nice.

For stylesheets, I used Clay. It was also new to me. I didn’t like it quite as much as Lucid because of some little oddities like alignSide and sym2. However I’m really just picking nits here. Clay is an excellent way to generate CSS in Haskell.

And finally I used JMacro for scripts. Instead of being a DSL, it’s a quasi-quoter for Template Haskell. That avoids the problem of embedding all of JavaScript inside Haskell. It adds some sugar on top of JavaScript, but I loved it because it caught syntax errors as part of my build process.

If you’re interested in more about how I built Blunt, go look at the source on GitHub. You’ll find all the nitty-gritty details over there. If you’re only interested in using it, be sure to bookmark blunt.herokuapp.com.