# Self-recursion and arrow functions

Jorge Chamorro jorge at jorgechamorro.com
Sun Mar 17 04:28:27 PDT 2013

```On 17/03/2013, at 12:16, Jason Orendorff wrote:

> On Sun, Mar 17, 2013 at 2:43 AM, Claus Reinke <claus.reinke at talk21.com> wrote:
> Neither arguments.callee (not available in strict) nor let (clumsy to
> use in expressions) are needed for self-reference
>
>    var rec = (f) => f((...args)=>rec(f)(...args));
>
>    var f = (self)=>(n)=> n>1 ? n*self(n-1) : n;
>
>    [1,2,3,4,5,6].map((n)=>rec(f)(n));
>
> ...but then you have a function rec which self-references. Much better to use the Z combinator:
>
>     f => (x => f(v => x(x)(v)))(x => f(v => x(x)(v)))
>
> which can be conveniently inlined into any expression where it's used:
>
>   js> [1,2,3,4,5,6].map((n)=>(f => (x => f(v => x(x)(v)))(x => f(v => x(x)(v))))(self => n => n>1 ? n*self(n-1) : n)(n));
>   [1, 2, 6, 24, 120, 720]
>
> Obviously this is much better than arguments.callee.

:-)

And I want to tear out my eyes!
--
(Jorge)();
```