A Tour of Go - Exercise: Loops and Functions - Part 3

exercise-loops-and-functions-part-3.go

// See https://gist.github.com/bilsalak/a53cddbee61647eea9de552193cfcedf for part 2
//
// Try other initial guesses for z, like x, or x/2. How close are your function's 
// results to the math.Sqrt in the standard library?
package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	z := (x / 2)
	last_z := z
	change := 1.0
	minimum_change := 0.000000000000001
	iteration := 0

	for change > minimum_change {
		z -= (z*z - x) / (2 * z)
		change = math.Abs(last_z - z)
		last_z = z
		iteration++
	}

	fmt.Println("This answer took ", iteration, " loop iterations")
	return z
}

func main() {
	for i := 1.0; i < 4; i++ {
		fmt.Println("calculating Sqrt of ", i, " using custom Sqrt function")
		fmt.Println(Sqrt(i))
		fmt.Println("calculating Sqrt of ", i, " using math.Sqrt function")
		fmt.Println(math.Sqrt(i))
	}
}