[harveywi]

The author had (too much) fun using a combination of the SKI combinator calculus [1] and the "B, C, K, W" system [2].

[1] https://en.wikipedia.org/wiki/SKI_combinator_calculus [2] https://en.wikipedia.org/wiki/B,_C,_K,_W_system

[maweki]

Isn't Haskell internally using a variant of the SKI combinator calculus to represent that all functions are data? This would mean less reduction for an already reduced program.

[lelf]

That would be true for a toy Haskell compiler. “The standard” Haskell compiler, GHC, can do a whole lot of optimisations and produces really good machine code nowadays.