Psellos
Contemporary Development With Functional Programming

OCaml iOS Apps Ported to Browser

February 24, 2020

Something like ten years ago we produced two iOS card game apps written in OCaml, partly as a proof of concept for compiling OCaml to iOS and partly because we enjoy card games. Unfortunately we weren’t able to spark a worldwide craze for writing iOS apps in OCaml or for playing Schnapsen, as we had hoped. Consequently there was very little financial return and we all had to move on to other projects.

Both apps play a very good two-player card game. The apps are essentially a kind of solitaire where you play against the app as your opponent. The games are:

  • Cassino, a classic fishing game said without substantiation to be of Italian origin (per Wikipedia).

  • Schnapsen, a kind of miniature Pinochle very popular in the territories of the former Austro-Hungarian Empire (again per Wikipedia).

The Schnapsen app also plays a closely related game called Sixty-Six, named after this number in many different languages.

The images and layout algorithms for the apps quickly fell behind the formats and display capabilities of later iOS devices, so I was thinking we might just as well release the apps as is, for free. However there is a lot of rigamarole (and some cost) associated with the App Store if all you want to do is release some free apps.


Cassino

Master
Schnapsen/66

Recently I wondered if it wouldn’t be possible to revive the apps in a browser environment. These days you can compile OCaml to JavaScript using BuckleScript or Js_of_ocaml. The HTML 5 canvas element has an interface a lot like the two-dimensional graphics used by the apps. It seems like it should be possible.

So, in fact, that’s what I did. I ported the two card game apps to run as webapps. Visually they run in a smallish rectangle exactly the size of the original iPhone screen. I was able to retain the iPhone behavior almost unchanged. Computationally they run completely in the browser, and make no further contact with psellos.com (unless you want to access the game pages at psellos.com).

The OCaml code is compiled to JavaScript using the BuckleScript compiler. Because the target language is JavaScript, there’s no need for any stubs or supporting code (as there was in iOS). All of the code for the apps is in OCaml.

Once the basic graphics primitives were in place, a lot of the code worked without any change. The part of the code that actually plays the game (the “engine”) didn’t change at all.

As an unexpected and very welcome side effect, two of the old iOS app team members got interested in the project again. They’re working on making the Schnapsen app into an even better player. I added some extra features to the Schnapsen GUI to make it easier to keep track of what’s happened in a hand.

Neither of the webapps is quite finished yet. But they both are already playable and in fact quite enjoyable. You can try them by clicking on the icons above. You can also read about the apps and the games they play on their own separate pages.

If you have any comments, suggestions, or encouragement, leave them below or email me at jeffsco@psellos.com.

Posted by: Jeffrey

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