A Tour of Go (http://tour.golang.org)

tour-23.go

// http://tour.golang.org/#23

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	z, prev := 1.0, 0.0
	for math.Abs(prev - z) > 0.0001 {
		prev = z
		z = z - (z * z - x) / (2 * z)
	}
	return z
}

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

tour-35.go

// http://tour.golang.org/#35

package main

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

func Pic(dx, dy int) [][]uint8 {
	pic := make([][]uint8, dy)
	for x := range pic {
		pic[x] = make([]uint8, dx)
		for y := range pic[x] {
			pic[x][y] = uint8((x + y) / 2)
		}
	}
	return pic
}

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

tour-40.go

// http://tour.golang.org/#40

package main

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

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

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

tour-43.go

// http://tour.golang.org/#43

package main

import "fmt"

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

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

tour-47.go

// http://tour.golang.org/#47

package main

import (
	"fmt"
	"math"
	"math/cmplx"
)

func Cbrt(x complex128) complex128 {
	z, prev := 1.0, 0.0
	for math.Abs(prev - z) > 0.0001 {
		prev = z
		z = z - (z * z * z - real(x)) / (3 * z * z)
	}
	return complex(z, imag(x))
}

func main() {
	fmt.Println(Cbrt(2))
	fmt.Println(cmplx.Pow(2, 0.3333333))
}