Proof, order of operations and functional languages
ajuc: I've tried version with 3 arguments (x,y,z) and 2 functions (+,/), and these two aproaches are not equivalent. For example:/(x,+(y,z)) has no equivalent expression that can be made from x f1 y f2 z if you permutate arguments or substitute functions (f1=/ f2 = +) or (f2=+ f1=/) because / binds stronger than +.