go-tour/exercise-loops-and-functions.go

package main

import (
    "fmt"
    "math"
)

func Sqrt(x float64) float64 {
    var p float64
    for z := 1.0; z != p && math.Abs(z - p) > 0.000000000000001; z -= (z * z - x) / (2 * z) {
        p = z
    }
    return p
}

func main() {
    fmt.Printf("Stdlib: %g, Mine: %g\n", math.Sqrt(333), Sqrt(333))
    fmt.Printf("Stdlib: %g, Mine: %g\n", math.Sqrt(33), Sqrt(33))
    fmt.Printf("Stdlib: %g, Mine: %g\n", math.Sqrt(17), Sqrt(17))
    fmt.Printf("Stdlib: %g, Mine: %g\n", math.Sqrt(4), Sqrt(4))
}