January 2021 1HaskellADay 1Liners

• 2021-01-28: Opposite problem:
  You have: [(a, Set b)]
  you want: [(a, b)]
  e.g.:  [("hi", fromList [1,2,3]), ("bye", fromList [4,6,7]) ->
  [("hi",1),("hi",2),("hi",3),("bye",4),("bye",6),("bye",7)]
  Interestingly, Set is not a Monad. wut. How do you get around that problem?
• D Oisín Kidney @oisdk (>>= traverse toList)
• mine: concatMap (sequence . second Set.toList)
• 2021-01-28: 
  We have [(Set a, b)]
  we want [(a, b)] 
  where each element of Set a is paired with b, e.g.:
  [(fromList [1,2,3], 'a'), (fromList [4,5,6], 'b')]
  becomes
  [(1,'a'),(2,'a'),(3,'a'),(4,'b'),(5,'b'),(6,'b')]
• Steve "wash your hands" Trout @strout:
  concatMap (uncurry (liftA2 (,)) . bimap toList pure)
• insatiable mask wearer @tim_1729
  [(a,b) | (s,b) <- xs, a <- (toList s)]
• Today, 2021/01/21, is:
1. Can be written with only 3 digits, What other dates can be so written? Also:
2. a day where the month and day are NOT amalgamation the year. But which dates are amalgamations?