A -. B NB. items in A but not in B
┌──────┐
│Serena│
└──────┘
A -.~ B NB. items in B but not in A
┌───┐
│Jim│
└───┘
A NB. A is a sequence without duplicates
┌────┬──────┬───┬────┐
│John│Serena│Bob│Mary│
└────┴──────┴───┴────┘