Changes:
- `scanr` now syncs the left ends of multiple inputs, as it should.
- robustness: add a typecheck to `ShadowedSequence.__init__`
- rename: for consistency with `rscanl`, `rfoldl`, the new names of *sync right ends of multiple inputs, then map/zip from the right*, are `rmap`, `rzip`.
- `llist`, `lreverse` are now more ducky/pythonic.
New:
- add `rscanl`, `rscanl1`, `rfoldl`, `rreducel`: reverse each input, then left-scan/left-fold. This approach syncs the right ends if multiple inputs.
- add `mapr`, `zipr` (map-then-reverse): sync left ends of multiple inputs, then map/zip from the right.
- add convenience function `rev`: try `reversed(...)`, if `TypeError` then `reversed(tuple(...))`
- add `butlast`, `butlastn`, `partition`
---