A (right) semigroup/monoid/group action of G on P is simply the implementation of a method actr(p, g), or p <|+| g, such that:
1. `p <|+| (g |+| h) === (p <|+| g) <|+| h` for all `g`, `h` in `G` and `p` in `P`.
2. `p <|+| id === p` for all `p` in `P` (if `id` is defined)
- Companion
- object