Golang iterator example 1.23

main.go

package main

import "fmt"

// Seq is an iterator over sequences of individual values.
// When called as seq(yield), seq calls yield(v) for each value v 
// in the sequence, stopping early if yield returns false.
// type Seq[V any] func(yield func(V) bool)

// our iterator function takes in a value and returns a func
// that takes in another func with a signature of `func(int) bool`
func Countdown(v int) func(func(int) bool) {
	// next, we return a callback func which is typically
	// called yield, but names like next could also be
	// applicable
	return func(yield func(int) bool) {
		// we then start a for loop that iterates
		for i := v; i >= 0; i-- {
			// once we've finished looping
			if !yield(i) {
				// we then return and finish our iterations
				return
			}
		}
	}
}

func main() {
	for x := range Countdown(10) {
		fmt.Println(x)
	}
}

to understand more about iterators https://medium.com/eureka-engineering/a-look-at-iterators-in-go-f8e86062937c