golang tour solutions

Go (tour) Exercises

// Exercise 25: Loops and Functions
///////////////////////////////////////

package main

import (
    "fmt"
    "math"
)

func Sqrt(x float64) float64 {
    
    const delta_threshold = 2.2000e-10
    
    z := 1.0
    last := x
    
    for math.Abs(last-z) > delta_threshold {
        last, z = z, z - (( z * z - x ) / ( 2 * z ))
        //fmt.Println(z, last, math.Abs(last-z))
    }
    return z
}

func main() {   
    fmt.Printf("Newtons Approx: %v, math.Sqrt: %v ", Sqrt(2), math.Sqrt(2))
}



// Exercise 38: Slices
///////////////////////////////////////

package main

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

func Pic(dx, dy int) [][]uint8 {
    
    // Create y slices
    picture := make([][]uint8, dy)
    
    // Create x slices
    for x := range picture {
        picture[x] = make([]uint8, dx)
    }
    
    // Generate integers
    for y := range picture {
        for x := range picture[y] {
            //picture[y][x] = uint8((x+y)/2)
            picture[y][x] = uint8(x*y)
        }
    }
    
    return picture
    
}

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