Functions to verify properties of a Set.
notEmpty : error -> Set a -> Result ( error, List error ) (Set a)
Fails if a Set is empty.
import Set
notEmpty "error" <| Set.empty
--> Err ( "error" , [])
notEmpty "error" <| Set.fromList [ (1, 1) ]
--> Ok <| Set.fromList [ (1, 1) ]