For the Haskellers in the room, the “K” combinator is “const”, and the “S” combinator is “ap” in the Reader monad. Combinators encode common patterns; for examp

For the Haskellers in the room, the “K” combinator is “const”, and the “S” combinator is “ap” in the Reader monad. Combinators encode common patterns; for example, you can use the fact that Sxyz = xz(yz) to write functions that split some input in two, do a computation on both parts, then join the results: capitalize = (:) . toUpper . head <*> map toLower . tail Of course, combinators rapidly become unwieldy for anything nontrivial, since they are the essence of point-free style. And most SK calculus terms aren’t typeable in Haskell anyway.