A tour of Go

exercises.go

// 25. Exercise: Loops and Functions
package main

import (
    "fmt"
    "math"
)

func Sqrt(x float64) float64 {
    z := float64(1)
    y := float64(0)
    for {
        z = z-(z*z-x)/(2*z)
        if math.Abs(z-y) < 1e-15 {
            return y
        }
        y = z
    }
}

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

// 38. Exercise: Slices
package main

import (
    "code.google.com/p/go-tour/pic"
)

func Pic(dx, dy int) [][]uint8 {
    result := make([][]uint8, dy);
    for x := 0; x < dy; x++ {
        result[x] = make([]uint8, dx);
        for y := 0; y < dx; y++ {
            result[x][y] = uint8(x^y);
            //result[x][y] = uint8((x+y)/2);
            //result[x][y] = uint8(x*y);
        }
    }
    return result;
}

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

// 43. Exercise: Maps
package main

import (
    "strings"
    "code.google.com/p/go-tour/wc"
)

func WordCount(s string) map[string]int {
    m := make(map[string]int)
    a := strings.Fields(s)
    n := len(a)
    for i := 0; i < n; i++ {
        (m[a[i]])++
    }
    return m
}

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

// 46. Exercise: Fibonacci closure
package main

import "fmt"

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

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

// 50. Advanced Exercise: Complex cube roots