How folds differ seems to be a frequent source of confusion, so here’s a more general overview: Consider folding a list of n values [x1, x2, x3, x4 … xn ] with some function f and seed z. foldl is: Left associative: f ( … (f (f (f (f z x1) x2) x3) x4) …) … Read more
A Y-combinator is a “functional” (a function that operates on other functions) that enables recursion, when you can’t refer to the function from within itself. In computer-science theory, it generalizes recursion, abstracting its implementation, and thereby separating it from the actual work of the function in question. The benefit of not needing a compile-time name … Read more