Function Closures in Golang

Go functions may be closures. A closure is a function value that references variables from outside its body. The function may access and assign to the referenced variables; in this sense the function is "bound" to the variables.

For example, the adder function returns a closure. Each closure is bound to its own sum variable.

func adder() func(int) int {
 sum := 0
 return func(x int) int {
  sum += x
  return sum
 }
}

func main() {
 pos, neg := adder(), adder()
 for i := 0; i < 10; i++ {
  fmt.Println(
   pos(i),
   neg(-2*i),
  )
 }
}