// `for` is Go's only looping construct. Here are
// some basic types of `for` loops.

package main

import "fmt"

func main() {

	// The most basic type, with a single condition.
	i := 1
	for i <= 3 {
		fmt.Println(i)
		i = i + 1
	}

	// A classic initial/condition/after `for` loop.
	for j := 7; j <= 9; j++ {
		fmt.Println(j)
	}

	// `for` without a condition will loop repeatedly
	// until you `break` out of the loop or `return` from
	// the enclosing function.
	for {
		fmt.Println("loop")
		break
	}

	// You can also `continue` to the next iteration of
	// the loop.
	for n := 0; n <= 5; n++ {
		if n%2 == 0 {
			continue
		}
		fmt.Println(n)
	}

	nums := []int{2, 3, 4}
	sum := 0
	for _, num := range nums {
		sum += num
	}

	// `range` on arrays and slices provides both the
	// index and value for each entry. Above we didn't
	// need the index, so we ignored it with the
	// blank identifier `_`. Sometimes we actually want
	// the indexes though.
	for i, num := range nums {
		if num == 3 {
			fmt.Println("index:", i)
		}
	}

	// `range` on map iterates over key/value pairs.
	kvs := map[string]string{"a": "apple", "b": "banana"}
	for k, v := range kvs {
		fmt.Printf("%s -> %s\n", k, v)
	}

	// `range` can also iterate over just the keys of a map.
	for k := range kvs {
		fmt.Println("key:", k)
	}

	// `range` on strings iterates over Unicode code
	// points. The first value is the starting byte index
	// of the `rune` and the second the `rune` itself.
	for i, c := range "go" {
		fmt.Println(i, c)
	}
}