A Tour of Go - Exercise: Loops and Functions http://tour.golang.org/#24

loops_and_functions.go

package main

import (
    "fmt"
    "math"
)


const e = 1e-8  // small delta

func Sqrt(x float64) float64 {
    /*
    Newton's method is to approximate Sqrt(x) by picking a 
    starting point z and then repeating: 
    z = z - ((z*z - x) / (2*z))
    */
    z := x  // starting point
    for {
        new_z := z - ((z*z - x) / (2*z))
        if math.Abs(new_z - z) < e {
            return new_z
        }
        z = new_z
    }
}

func main() {
    fmt.Println(Sqrt(2))
    fmt.Println(math.Sqrt(2))
}