Earlier quoted context omitted.
Hmm! That's funny, I thought I was "getting" monads better after reading this article (as someone who doesn't already have a firm grasp of monads, of course). You see, I already sensed that monads: - were a way that you could sort of simulate side effects using pure functions - had to do with the type signatures of functions What I gleaned from the article is that monads: - have to do with making functions composable…
Monads basically let you add an extra calculation to your functions. Why would you want to do that? Mainly so that you don't have to do it manually. Think of it as tacking an extra calculation onto the side of each function that operates in the monad. For a "state" monad, that calculation is maintaining/passing the state. For a "logging" monad, that calculation is maintaining the log. For an "error handling monad", t…
Take the OP's example for the Writer monad, in which several functions needed to return a debug string " was called" in addition to their main return value. If I had these two functions+:
(def sine (x)
[(Math.sin x) "sine was called"])
(def cube (x)
[(* x x x) "cube was called"])
(mac defWriter (name parms body...)
`(def ,name ,parms
[,@body (+ ,name " was called.")]))
(defWriter sine (x)
(Math.sin x))
(defWriter cube (x)
(* x x x))
+ Forgive me for indulging in the syntactic sugar from my own lisp->javascript project in these examples, but since we're dealing in JavaScript I couldn't resist. https://github.com/evanrmurphy/lava-script