Tuesday July 17th

GSoC Day 65

Working on Haskell tonight

  • I’m currently working through Hbook, particularly trying to get better at type-checking and type-classes. So I’m redoing exercises before I go on. Today, I read about existential quantifiers and existential types. I’m trying to do this by carrying around a notebook where I write and deconstruct everything. The only thing about doing that is that I can’t remember everything, so sometimes when I’m asked something on the spot, I feel the need to refer to my book, which is kind of annoying, but whatever.

  • At work today, I got a good amount of work done. I had my headphones on and just barrelled through a good bit of it. In between, of course I wrote Haskell :) I also met someone on my floor randomly who started talking to me and soon I was telling him about Coq and Idris and Agda. And he was fascinated and wanted to know more and said he was interested in learning more, too. So I told him to come to our PureScript LA Meetup :) So that would be kind of cool. I think I’ll get him hooked haha.

  • Today for our GSoC session, we worked on debugInteractionOf. I got to write my first programme for CodeWorld using interactionOf. I have to say in all my reading, I haven’t seen one InteractionOf programme that is less than say, 20 lines. So this clarified a lot for me.

  • Specifically, it was
     import CodeWorld
     main :: IO ()
     main = interactionOf state0 step event draw
     state0 = (0, 0)
     step dt state = state
     event (PointerPress pt) state = pt
     event _ state = state
     draw (x,y) = translated x y (circle 1) 
  • You can try it out here. Hint: Click on the circle

  • So it looks like interactionOf takes an initial state, a step, which is the derivative by which the state changes, driven by an event (eg. a Mouse Click) and draws to a picture type (ie a picture). In this case, the state after the PointerPress (ie MouseClick) is the new state, because the point at which it is clicked is the new point. The picture is translated to the point x y of circle with radius 1.


  • Back to work for me. I also found a broken link on Haskell documentation. If I were certain of the correct one, I would have made a pull-request, but I just filed an issue for now.

  • Also, I’m working on an issue for another Open Source project. I’m also excited about that. So continuing to work on Open Source daily :)


  • I want a sticker that says “Is that a piece of dust on my computer screen or is that expression point free?”. Seriously caught myself saying this today! :)
Written on July 17, 2018