Recursions without names: Introduction to the Y combinator in JavaScript

Post by viebel » Fri, Aug 12, 2016, 11:30 AM UTC

hughbetcha wrote: post #21

To be fair, the article would be more aptly titled "Recursion without function names". In any recursion you need a way to reference the original function somehow. They're using a function parameter to accomplish that via indirection.

Post by prashnts » Fri, Aug 12, 2016, 11:53 AM UTC

viebel wrote: post #19

prashnts wrote: post #17

I find the Python implementation is slightly more elegant: (lambda f: f(f)) (lambda fn: lambda n: 1 if n == 0 else (n * fn(fn)(n - 1))) (5)

Yeah. But I didn't find a way to run python code in the browser. Currently in Klipse, we support javascript, ruby, clojure and php...

Post by qwertyuiop924 » Fri, Aug 12, 2016, 12:52 PM UTC

gohrt wrote: post #14

qwertyuiop924 wrote: post #6

Earlier quoted context omitted.

Quoth xkcd, "Tail recusion is its own reward." In all seriousness, even if the y combinator is practically useless in languages that don't have proper TCO (which is specced for ES7), it's a useful learning tool, is powerfully mind expanding, and can help to demonstrate the power of the λ-calculus.

Is the Y-combinator any more or less dependent on TCO than regular recursion? The Y combinator is useless in languages that already have builtin support for recursive functions.

Post by agumonkey » Fri, Aug 12, 2016, 2:22 PM UTC

furhxbbd wrote: post #4

For what purpose?

Post by hughbetcha » Fri, Aug 12, 2016, 3:54 PM UTC

viebel wrote: post #22

hughbetcha wrote: post #21

To be fair, the article would be more aptly titled "Recursion without function names". In any recursion you need a way to reference the original function somehow. They're using a function parameter to accomplish that via indirection.

There are no names except function arguments. No 'x=...'