Tour of Go exercises

exercise-fibonacci-closure.go

// https://tour.golang.org/moretypes/22

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	n1, n2 := 1,1
	return func() int {
		n1, n2 = n2, n1+n2
		return n2
	}
}

func main() {
	f := fibonacci()
	for i := 0; i < 10; i++ {
		fmt.Println(f())
	}
}

exercise-loops-and-functions.go

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	z1, z2 := 1.0, 1.0
	maxerr := 0.0001
	for {
		z1 = z1 - (z1*z1-x)/(2*z1)
		if math.Abs(z2-z1) < maxerr {
				return z1
		}
		z2 = z1
	}
}

func main() {
	n := 2.0
	fmt.Println(Sqrt(n), math.Sqrt(n), math.Abs(Sqrt(n)-math.Sqrt(n)))
}

exercise-maps.go

// https://tour.golang.org/moretypes/19

package main

import (
	"strings"
	"golang.org/x/tour/wc"
)

func WordCount(s string) map[string]int {
	words := strings.Fields(s)
	count := make(map[string]int)
	for _, word := range words {
		count[word]++
	}
	return count
}

func main() {
	wc.Test(WordCount)
}

exercise-slices.go

// https://tour.golang.org/moretypes/14

package main

import "golang.org/x/tour/pic"

func Pic(dx, dy int) [][]uint8 {
	img := make([][]uint8, dy)
	for i := 0 ; i < dy ; i++ {
		img[i] = make([]uint8, dx)
		for j := 0 ; j < dx ; j++ {
			img[i][j] = uint8(i*j)
		}
	}
	return img
}

func main() {
	pic.Show(Pic)
}

exercise-stringer.go

// https://tour.golang.org/methods/7

package main

import "fmt"

type IPAddr [4]byte

// TODO: Add a "String() string" method to IPAddr.
func (ip IPAddr) String() string {
	return fmt.Sprintf("%d.%d.%d.%d", ip[0], ip[1], ip[2], ip[3])
}

func main() {
	addrs := map[string]IPAddr{
		"loopback":  {127, 0, 0, 1},
		"googleDNS": {8, 8, 8, 8},
	}
	for n, a := range addrs {
		fmt.Printf("%v: %v\n", n, a)
	}
}