I do not know whether there is a deeper connection between `S`

and `K`

being functionally complete and monadic structure.

If by *“functionally complete”*, you mean Turing-complete then yes - the `Applicative`

instance for the partially-applied function type `(->) r`

:

```
instance Applicative ((->) r) where
pure = \ a b -> a
(<*>) = \ f g x -> f x (g x)
```

…is Turing-complete (I think Ben Lynn also makes some comments about the `Applicative`

-`S`

-`K`

connection in his presentation at Zurihac 2023). Therefore *all computable functions* can be defined (albeit very verbosely!) using `pure`

and `(<*>)`

for the `Applicative`

reader `type Reader r a = (->) r a`

.

Getting back on-topic - while Raymond Smullyan’s book *To Mock a Mockingbird* (1985), as mentioned earlier:

`https://discourse.haskell.org/t/combinatory-logic/8380/14`

…goes well beyond the `S`

and `K`

combinators, its memorable presentation of combinatory logic makes it a worthy addition to the collection of *“offline”* resources.