Y Combinator in Go

YFact.go

package main

import "fmt"

//based on code from http://www.arcfn.com/2009/03/y-combinator-in-arc-and-java.html

type Func func (interface{}) interface{}

type FuncToFunc func (Func) Func

type FuncToTFunc func (FuncToTFunc) Func

func Y(r FuncToFunc) Func {
	return func(f FuncToTFunc) Func {
		return f(f)
	}(func(f FuncToTFunc) Func {
		return r(func(x interface{}) interface{} {
			return f(f)(x)
		})
	})
}

func main() {
	fmt.Println(Y(func(f Func) Func {
		return func(n interface{}) interface{} {
			nn := n.(int)
			if nn == 0 {
				return 1
			}
			return nn * (f(nn-1)).(int)
			
		}
	})(5))
}