A Y Combinator in go

y.go

package main

import (
	"fmt"
)

// A Y Combinator (Only for func(int) int, so not *the* y combinator)
func Y(f func(func(int) int) func(int) int) func(int) int {
	return f(func(x int) int {
		return Y(f)(x)
	})
}

func nearFactorial(f func(int) int) func(int) int {
	return func(n int) int {
		if n == 0 {
			return 1
		}
		return n * f(n-1)
	}
}

func main() {
	factorial := Y(nearFactorial)
	for i := 0; i < 20; i++ {
		fmt.Printf("%v! = %v\n", i, factorial(i))
	}
}