[Go] Higher-order function: zip

package main

import (
    "fmt"
)

type Tuple struct {
    First  int
    Second int
}

func zip(m []int, n []int) func() (Tuple, bool) {
    if len(m) != len(n) {
        panic("Unequal list length")
    }

    i := -1
    return func() (Tuple, bool) {
        i += 1
        if i < len(m) {
            return Tuple{First: m[i], Second: n[i]}, true
        } else {
            return Tuple{First: 0, Second: 0}, false
        }
    }
}

func main() {
    m := []int{1, 2, 3}
    n := []int{4, 5, 6}

    // Get the iterator
    iter := zip(m, n)

    // Iterate through the list.
    for {
        out, ok := iter()
        if !ok {
            break
        }

        fmt.Println(out)
    }
}