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 {
    idx, beforeLastN, lastN := 0, 0, 1
    return func() int {
        if (idx == 0) {
            idx++
            return beforeLastN
        }
        if (idx == 1) {
            idx++
            return lastN
        }
        sum := beforeLastN + lastN
        beforeLastN = lastN
        lastN = sum
        return sum
    }
}

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