Wow, cool. Thanks for sharing the link! (the code is in English, only the comments are in French)

One rather minor question: Is writing comments or even code in the local language still common in France? Afaik, in most European countries the CS courses are taught in English.

I mostly write my assignments in French. It just feels "strange" to me to write comments (which are just real sentences) in English when anyone which will read the thing shares my native language. When I'm comment complex things (like some parts of this compiler), I feel it easier and more comprehensive to explain them in my mother tongue.

Anyway, I write all of my "public code" in English. The audience is different.

> Afaik, in most European countries the CS courses are taught in English.

Not really. You only write stuff in English if it intended for publication like papers and stuff.

He is from Belgium, and it is not common. Maybe it was a requirement for his course.

All the literature, programming libraries etc. have corrupted my brain to the point that I write my code in English when it's only for my own eyes, even though it isn't my native tongue.

I do the same. :)

Re. GADTs, you can parse to an ADT then have a separate function to add the extra type information. The problem is that you want to add static information to dynamic input, so you need to handle the error cases.

Yep. I tought about it, but I was a few days from the deadline date, and this will add a significant amount of work.

Anyway, I was dissatisfied of that. GADTs are awesome to add some "proofness" to a type checker.