Haskell `Data.List` functions.

- [x] `last` + `init`
- [ ] `foldl`?
- [ ] `scan`
- [ ] Better `repeat`?
- [x] `take`, `drop`, `splitAt`
- [ ] `span`, `break`
- [ ] `isPrefixOf`, `isSuffixOf`, `isInfixOf`, `isSubsequenceOf`
- [X] Proper `find` with predicates?