fold is a library function that is very general, and would be built-in in most other languages (if it existed at all). You wouldn’t write most functions like th

fold is a library function that is very general, and would be built-in in most other languages (if it existed at all). You wouldn’t write most functions like that. A long variable name only makes sense when the variable is specific. In fold, you have “a function”; nothing else can be said about it. And since working with “a function” is very common, Haskell programmers have converged on a shorthand for it: f. Sure, it’s harder for an entirely new programmer to understand, but every language has practices like this that need to be learned: take “i” in a for-loop in C.