There are a lot of languages where even if you don't know that language, you can figure out what's happening. I have no idea what your example is supposed to do.
That's because it's taken from a library that deals with graphs[1]. I had to look it up, because I had no idea what it does either and I know Haskell. Here's a better example of what he meant in Elm, a language that looks a lot like Haskell:
https://github.com/bryanjenningz/25-elm-examples/blob/master...
[1]: http://hackage.haskell.org/package/fgl-5.7.0.1/docs/Data-Gra...