tour of go memo

tour24.go

package main

import (
    "fmt"
    "math"
)

const RepeatTimes = 3

func Sqrt(x float64) float64 {
    z := float64(1)
    for i := 0; i < RepeatTimes; i++ {
        z = newton(x, z)
    }
    return z
}

func Sqrt_AutoStop(x float64) float64 {
    z1 := float64(1)
    z2 := newton(x, z1)
    for math.Abs(z1 - z2) > float64(1e-15) {
        z1 = z2
        z2 = newton(x, z2)
    }
    return z2
}

func newton(x float64, z float64) float64 {
    return z - (math.Pow(z, 2) - x) / (2 * z)
}

func main() {
    fmt.Println(Sqrt(2))
    fmt.Println(Sqrt_AutoStop(2))
    fmt.Println(math.Sqrt(2))
    // 1.4142156862745099
    // 1.414213562373095
    // 1.4142135623730951
}

tour36.go

package main

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

func Pic(dx, dy int) [][]uint8 {
    canvas := make([][]uint8, dx)
    for i := 0; i < dx; i++ {
        row := make([]uint8, dy)
        canvas[i] = row
    }

    for x := 0; x < dx; x++ {
	    for y := 0; y < dx; y++ {
            f := powrainbow // change me
            canvas[x][y] = uint8(f(x, y))
        }
    }
    
    return canvas
}

// 遊び過ぎ...
func grad(x, y int) int { return x ^ y % 8 }
func para(x, y int) int { return x ^ y }
func mid(x, y int) int { return (x + y) / 2 }
func circ(x, y int) int { return x * x + y * y }
func bi(x, y int) int { return x * y }
func tri(x, y int) int { return x * x * x + y * y * y }
func powrainbow(x, y int) int {
    return int((math.Pow(float64(x), 0.5)  +
                math.Pow(float64(y), 0.5)) * 32)
}

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

tour41.go

package main

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

func WordCount(s string) map[string]int {
    aMap := make(map[string]int)
    splitBy := func(c rune) bool {
        return unicode.IsSpace(c)
    }
    fields := strings.FieldsFunc(s, splitBy)
    
    for _, word := range(fields) {
        if _, ok := aMap[word]; ok {
            aMap[word] += 1
        } else {
            aMap[word] = 1
        }
        
    }

    return aMap
}

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

tour44.go

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
    var i, j, j2 = 1, 0, 0
    return func() int {
        j2 = i + j
        i, j = j, j2
        return j2
    }
}

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

tour48.go

package main

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

func Cbrt(x complex128) complex128 {
    newton := func(xi complex128, zi complex128) complex128 {
         return zi - (zi * zi * zi - xi) / (3 * zi * zi)
    }
    
	z1 := complex128(1)
	z2 := newton(x, z1)
	for cmplx.Abs(z1 - z2) > float64(1e-15) {
		z1 = z2
		z2 = newton(x, z2)
	}
	return z2
}

func main() {
    fmt.Println(Cbrt(27))
    fmt.Println(math.Pow(27, (1.0/3.0)))
    fmt.Println(cmplx.Pow(27, (1.0/3.0)))

    fmt.Println(Cbrt(5))
    fmt.Println(math.Pow(5, (1.0/3.0)))
    fmt.Println(cmplx.Pow(5, (1.0/3.0)))
}
/*
    (3+0i)
    2.9999999999999996
    (2.9999999999999996+0i)
    (1.709975946676697+0i)
    1.7099759466766968
    (1.7099759466766968+0i)
*/

tour36 / powrainbow の例。きれい？

50から続き。　http://go-tour-jp.appspot.com/#50