There and back again (TABA)

taba.hs

-- https://doisinkidney.com/posts/2020-02-15-taba.html

zipRev :: [a] -> [b] -> [(a,b)]
zipRev xs ys = foldl f b ys xs
  where
    b _ = []
    f k y (x:xs) = (x,y) : k xs
    f k y [] = []

{-

zipRev [1,2,3] [10,20,30] =
foldl f b [10,20,30] [1,2,3] =
(f (f (f b 10) 20) 30) [1,2,3] =
(1,30) : (f (f b 10) 20) [2,3] =
(1,30) : (2, 20) : (f b 10) [3] =
(1,30) : (2, 20) : (3, 10) : b [] =
(1,30) : (2, 20) : (3, 10) : [] =
[(1,30), (2,20), (3,10)]

-}