A Tour of GoのExerciseの解答

Exercise: Loops and Functions

package main

import (
    "fmt"
)

func Sqrt(x float64) float64 {
    z := 5.0
    for i := 0; i <= 10; i++ {
        z = z - (z * z - x) / (2.0 * z)
    }
    return z
}

func main() {
    fmt.Println(Sqrt(2))
}

Exercise: Slices

package main

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

func Pic(dx, dy int) [][]uint8 {
    // 一旦、2次元配列を0で初期化
    result := make([][]uint8, dy)
    for i := range result {
        result[i] = make([]uint8, dx)
    }

    for y := 0; y < dy; y++ {
        for x := 0; x < dx; x++ {
            //result[x][y] = uint8((x + y) / 2)
            //result[x][y] = uint8(x * y)
            result[x][y] = uint8(x ^ y)
        }
    }

    return result
}

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

Exercise: Maps

package main

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

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

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

Exercise: Fibonacci closure

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
    var f0, f1, f2 int = 0, 1, 0
    return func() int {
        fib := f0
        f2 = f0 + f1
        f0 = f1
        f1 = f2
        return fib
    }
}

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