intersection, union, difference, symmetric difference for dictionaries

[Ben Finney]

Peter Otten <__peter__ at web.de> writes:

> mauro wrote:
>
> > - Dictionaries and sets are both accessed by key
>
> but sets have no values

Or rather, sets *only* have values. Dictionaries have keys, sets do not
have keys.

-- 
 \         “If nature has made any one thing less susceptible than all |
  `\    others of exclusive property, it is the action of the thinking |
_o__)                          power called an idea” —Thomas Jefferson |
Ben Finney