A Tour of Go - Exercise: Loops and Functions - Part 1

exercise-loops-and-functions-part-1.go

// As a way to play with functions and loops, let's implement a square root function: given a number x, 
// we want to find the number z for which z² is most nearly x.
//
// Computers typically compute the square root of x using a loop. Starting with some guess z, 
// we can adjust z based on how close z² is to x, producing a better guess:
//
// z -= (z*z - x) / (2*z)
// Repeating this adjustment makes the guess better and better until we reach an answer that is as close 
// to the actual square root as can be.
//
// Implement this in the func Sqrt provided. A decent starting guess for z is 1, no matter what the input.
// To begin with, repeat the calculation 10 times and print each z along the way. See how close you get to 
// the answer for various values of x (1, 2, 3, ...) and how quickly the guess improves.
//
// Hint: To declare and initialize a floating point value, give it floating point syntax or use a conversion:
//
// z := 1.0
// z := float64(1)
package main

import (
	"fmt"
)

func Sqrt(x float64) float64 {
	z := 1.0
	for i := 0; i < 10; i++ {
		z -= (z*z - x) / (2 * z)
		fmt.Println(z)
	}

	return z
}

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