Anyone got a good explanation of "combinators" (Y-combinators etc. and NOT the company) I'm looking for one for the practical programmer who understands recursion and higher-order functions, but doesn't have a strong theory or math background. (Note that I'm talking about these things : http://en.wikipedia.org/wiki/Y_combinator ) ...
I'm interested in actual examples of using fixed point combinators (such as the y-combinator in C++. Have you ever used a fixed point combinator with egg or bind in real live code? I found this example in egg a little dense: void egg_example() { using bll::_1; using bll::_2; int r = fix2( bll::ret<int>(...
A regular function can contain a call to itself in its definition, no problem. I can't figure out how to do it with a lambda function though for the simple reason that the lambda function has no name to refer back to. Is there a way to do it? How? ...
I've been reading a bit lately about functional programming and I am trying to grok the Y-Combinator. I understand that you can use the Y-Combinator to effectively implement recursion in a language that doesn't support recursion directly. However, every language that I'm likely to use already supports recursion so I'm not sure how usef...
Take this example code (ignore it being horribly inefficient for the moment) let listToString (lst:list<'a>) = ;;' prettify fix let rec inner (lst:list<'a>) buffer = ;;' prettify fix match List.length lst with | 0 -> buffer | _ -> inner (List.tl lst) (buffer + ((List.hd lst).ToString())) inner lst "" ...
In almost all examples, a y-combinator in ML-type languages is written like this: let rec y f x = f (y f) x let factorial = y (fun f -> function 0 -> 1 | n -> n * f(n - 1)) This works as expected, but it feels like cheating to define the y-combinator using let rec .... I want to define this combinator without using recursion, using t...
The Y-combinator is defined as: Y = λf. (λx. f (x x)) (λx. f (x x)) Using this combinator, you can write recursive lambda functions or intercept recursive methods with custom code. How is the Y-combinator written in various languages? I'd be interested in seeing the Y-combinator defined and used to implement a recursive factorial fu...
I am confused about something. I wanted to generate an example (in Clojure) demonstrating how a fixed point combinator could be used to evaluate the fixed point of a sequence that mathematically converges after an infinite number of applications but would, in fact, converge after a finite number of steps due to finite precision of floati...
Doing the Y-Combinator for a single argument function such as factorial or fibonacci in Clojure is well documented: http://rosettacode.org/wiki/Y_combinator#Clojure My question is - how do you do it for a two argument function such as this getter for example? (Assumption here is that I want to solve this problem recursively and this n...
Curios to know, which of Y Combinators investments has financially been the most successful. Seems like everyone points our Reddit.com, but from what I gathered - the site wasn't really sold for all that much money. ...