package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
// from cpython/Doc/build/html/library/functools.html
// [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610]
func fibonacci() func() int {
	cur_fib := 0
	nxt_fib := 0
	return func() int {
		if nxt_fib == 0 {
            nxt_fib = 1
			return 0
		}
		tmp := cur_fib
		cur_fib = nxt_fib
		nxt_fib += tmp
		return cur_fib
	}
}

func main() {
	f := fibonacci()
	for i := 0; i < 20; i++ {
		fmt.Println(f())
	}
}