package main

import "fmt"

// 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.
func intSeq() func() int { //returns a function that returns an int
	i := 0              // i is a variable that intSeq's function value will reference. It continues to exist even after intSeq returns.
	return func() int { // the anonomous function is returned here. It is not executed yet.
		i++
		return i
	}
}

func main() {

	//functions are first class citizens in Go, so we can assign them to variables,
	// pass them as arguments to other functions, and return them from functions.
	nextInt := intSeq()

	fmt.Println(nextInt())
	fmt.Println(nextInt())
	fmt.Println(nextInt())

	//a second function value from intSeq, with its own i variable.
	newInts := intSeq()
	fmt.Println(newInts())
}