FP

People are saying avoid Monad “tutorials” [written by unqualified retards] , so writing down one is an IQ test and understanding is a “filter”. And, indeed, one has to know and understand some related concepts and become to a certain kind of mathematical thinking, otherwise one would apply bullshit imperative programming concepts instead of mathematical ones. The first concept is “composition of functions”, the famous \(\circ\) operator of the traditional mathematical notation. it takes two functions (of a single argument) and produces a new function (of a single argument, which is operationally defined is nesting of function calls. ...

A product-type is a generalized notion of having a bunch of things at the same physical locality (or proximity) – this and [also] that. This is what molecules are. A sum-type is a generalized abstract notion of having this-or-that (either-this-or-that, and NOT both). This is, among other things, a “fork” on a path – never both can be taken (except when backtracking). These notions are enough for everything and they are our basic building blocks. ...