A Tour of Go Exercise: Errors

exercise-errors.go

package main

import (
	"fmt"
	"math"
)

type ErrNegativeSqrt float64

func (e ErrNegativeSqrt) Error() string {
    return fmt.Sprintf("cannot Sqrt nagative number: %g", e)
}

func Sqrt(x float64) (float64, error) {
	z := 1.0
	if x < 0 {
		return 0, ErrNegativeSqrt(x)
	}
	for {
		z2 :=  z - (z * z - x) / (z * 2)
		if math.Abs(z2 - z) < 1e-10 {
			break
		}
		z = z2
	}
	return z, nil
}

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