Exercise made during A Tour of Go.

exercise.tour.go

/* 
* Exercise: Loops and Functions
* As a way to play with functions and loops, implement the square root function using Newton's method.
* To begin with, repeat the calculation 10 times and see how close you get to the answer for various values (1, 2, 3, ...).
* Next, change the loop condition to stop once the value has stopped changing (or only changes by a very small amount).
* See if that's more or fewer than 10 iterations. How close are you to the math.Sqrt?
*/

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	z := 1.0
	s := 0.0
	for i:= 0; i < 10; i++ {
		z -= (z*z - x) / (2*z)
		if math.Abs(s - z) < 1e-15 {
			fmt.Printf("Nuber of iteration %v \n", i)
			break
		}
		s = z
	}
	return z
}

func main() {
	val := 164.0
	fmt.Println("Newton", Sqrt(val))
	fmt.Println("Native", math.Sqrt(val))
}