tour of go

exercise-fibonacci-closure.go

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	i, j := 0, 1
	return func() int {
		k := i
		i, j = j, i+j
		return k
	}
}

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

exercise-images.go

package main

import (
	"golang.org/x/tour/pic"
	"image/color"
	"image"
)

const gridsize = 200

type Image struct{
	grid [gridsize][gridsize][3]uint8
}

func (i Image) ColorModel () color.Model {
	return color.RGBAModel
}

func (i Image) Bounds() image.Rectangle {
	return image.Rect(0, 0, gridsize, gridsize)
}

func (i Image) At(x, y int) color.Color {
	return color.RGBA{i.grid[x][y][0], i.grid[x][y][1], i.grid[x][y][2], 255}
}

func main() {
	m := Image{}
	for x := 0; x < gridsize; x++ {
		for y := 0; y < gridsize; y++ {
			m.grid[x][y][0] = (uint8)((x^y) * (x+y))
			m.grid[x][y][1] = (uint8)((x+y) * (x-y))
			m.grid[x][y][2] = (uint8)((x+y) * (x*y))
		}
	}
	pic.ShowImage(m)
}

exercise-maps.go

package main

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

func WordCount(s string) map[string]int {
	d := make(map[string]int)
	for _, w := range strings.Fields(s) {
		d[w] += 1
	}
	return d
}

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

exercise-stringer.go

package main

import "fmt"

type IPAddr [4]byte

func (i IPAddr) String() string {
	return fmt.Sprintf("%d.%d.%d.%d", i[0], i[1], i[2], i[3])
}

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

exercise_equivalent_binary_trees

package main

import (
	"golang.org/x/tour/tree"
	"fmt"
)

// Walk walks the tree t sending all values
// from the tree to the channel ch.
func Walk(t *tree.Tree, ch chan int) {
	if t.Left != nil {
		Walk(t.Left, ch)
	}
	ch <- t.Value
	if t.Right != nil {
		Walk(t.Right, ch)
	}
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *tree.Tree) bool {
	ch1 := make(chan int)
	ch2 := make(chan int)
	
	go Walk(t1, ch1)
	go Walk(t2, ch2)
	
	for i:=0; i<10; i++ {
		if <-ch1 != <-ch2 {
			return false
		}
	}
	return true
}

func main() {
	fmt.Println(Same(tree.New(1), tree.New(2)))
}