Comment by tuveson

Digging through the current Haskell standard library - for_ calls traverse_, which calls foldr, which calls foldMap, which calls… foldr. Found the recursion! The person you’re replying to is correct - you can mimic the style of a for loop, but under the hood all of this stuff is going to be implemented with recursion (and tail recursion, if you don’t want to hate your life).

I also may have gotten some detail slightly wrong, the code in Data.Foldable is kinda weird and I haven’t Haskell’d in a while