I worked for a startup that used clojure and found it so frustrating because, following the idiomatic style, pathways passed maps around, added keys to maps, etc. For any definition which received some such map, you had to read the whole pathway to understand what was expected to be in it (and therefore how you could call it, modify it, etc).

I think the thing is that yes, `[a] -> [a]` tells you relatively little about the particular relationship between lists that the function achieves, but in other languages such a signature tells you _everything_ about:

- what you need to call invoke it

- what the implementation can assume about its argument

i.e. how to use or change the function is much clearer