GUI programming in functional and logic languages tends to feel quite hard. There is nothing intrinsic in FP that makes GUI programming extra hard, but when everywhere else you are surrounded by nice, abstract, compositional, high-level descriptive definitions, working at the GUI’s low level feels… well, like you’re doing something wrong. ...

While code written in Haskell is very declarative and mathematical, as soon as we try to create a user interface, we’ll be slapped on the cheek by a wave of IO that will turn our code procedural in no time. One of the main ideas behind this gaming (ad)venture called Keera Studios is to write more mathematical, robust games. We want these games to be easy to understand and expand, and we want them to look good too. The current trend in this respect is based mostly on FRP. However, FRP is still on its way, and no Haskell implementation (AFAWK) performs really well. (We recently tried all of them, and found that there’s still a lot to be done to be able to fully rely on FRP for interactive applications). In this post we’ll see that, through an ad-hoc layer that will hide most of the controller and separate the UI from the mathematical model, we can implement nice-looking games in Haskell that have declarative, pure definitions and use graphics efficiently for the implementation. ...