Solution to http://tour.golang.org/#24. Find the square root a number using Newton Raphson method

newtonraphson.go

package main

import (
    "fmt"
)

func approx(z, x float64) float64 {
    z = z - (z*z - x)/2/z
    return z
    
}

func mod(x float64) float64 {
    if x < 0.0 {
    	x = -x    
    }
    return x   
}

func goodEnough(before, after float64) bool {
    change := (after - before)/before
    return mod(change) < 0.000000001
}

func Sqrt(x float64) float64 {
    before := 1.0
    after := 1.0
    iterations := 0
    for {
        iterations += 1
        after = approx(before, x)
        fmt.Println("Iterations: ", iterations)

        if goodEnough(after, before) {
        	break    
        }

        before = after
    }
    return after
}

func main() {
    fmt.Println(Sqrt(2))
    fmt.Println(Sqrt(1e6))
    fmt.Println(Sqrt(1/1e6))
}