A Tour of Go - Exercise: Errors

exercise-errors.go

// https://tour.golang.org/methods/20
package main

import (
	"fmt"
)

type ErrNegativeSqrt float64

func (e ErrNegativeSqrt) Error() string {
	return fmt.Sprintf("cannot Sqrt negative number: %v",
					   float64(e)) 
	// convert to float64: https://stackoverflow.com/a/27475316/959505
}

func Sqrt(x float64) (float64, error) {
	if x < 0 {
		return 0, ErrNegativeSqrt(x)
	}
	z := 1.0
	for i := 0 ; i < 10 ; i++ {
	    z -= (z*z - x) / (2*z)
	}
	return z, nil
}

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