Very interesting, important, and useful stuff. The only problem, IMO, is that they go nuts with the notation. (They call it "Squiggol"! https://en.wikipedia.

Very interesting, important, and useful stuff. The only problem, IMO, is that they go nuts with the notation. (They call it "Squiggol"! https://en.wikipedia.org/wiki/Squiggol https://en.wikipedia.org/wiki/Squiggol "Bird–Meertens formalism" ) I worked out §2 in Joy (a concatinative language) if anyone's interested: https://joypy.osdn.io/notebooks/Recursion_Combinators.html https://joypy.osdn.io/notebooks/Recursion_Combinators.html (I kind sorta started to approach §3 & §4 in https://joypy.osdn.io/notebooks/Treestep.html https://joypy.osdn.io/notebooks/Treestep.html but I didn't get far, I got sick of grokking squiggol.) The underlying ideas are interesting, important, and useful but I feel like the effort is kind of wasted if they can't "bring it down the mountain" to the average programmer, eh?