Exercise: Fibonacci closure

fibonacci.go

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
    pre := 0
    post := 1
    return func() int{
        sum := pre + post
        pre, post = post, sum
        return sum   
    }
}

func main() {
    f := fibonacci()
    for i := 0; i < 10; i++ {
        fmt.Println(f())
    }
}