Exercise: Loops and Functions - http://tour.golang.org/#25

Exercise-Loops-and-Functions.go

package main

import (
    "fmt"
    "math"
)

func Sqrt(x float64) float64 {
    guess := x
    for i := 0; i < 10; i++ {
        guess -= (math.Pow(guess,2) - 2) / (2.0*guess)
    }
    return guess
}

func SqrtDiff(x, y float64) float64 {
    diff := float64(math.Sqrt(x)) - y
    if diff < 0 {
       diff = -diff
    }
    return diff
}

func main() {
    fmt.Println(Sqrt(2))
    fmt.Println(math.Sqrt(2))
    fmt.Println(float64(math.Sqrt(2)) - Sqrt(2))
    fmt.Println(SqrtDiff(2, Sqrt(2)))
}

Output:

1.414213562373095
1.4142135623730951
2.220446049250313e-16
2.220446049250313e-16

Program exited.