A Tour of Go. Exercise: Errors. Copy your Sqrt function from the earlier exercises and modify it to return an error value. Sqrt should return a non-nil error value when given a negative number, as it doesn't support complex numbers. Create a new type type ErrNegativeSqrt float64 and make it an error by giving it a func (e ErrNegativeSqrt) Error(…

exercise-56.go

package main

import (
    "fmt"
)

type ErrNegativeSqrt float64

func (e ErrNegativeSqrt) Error() string {
    return fmt.Sprintf("cannot Sqrt negative number: %v", float64(e))
}


func Sqrt(f float64) (float64, error) {
    if f < 0 {
        return 0, ErrNegativeSqrt(f)
    }
    z := 1.0
    for i := 1; i <= 10; i++ {
        z = z - (z * z - f) / (2 * z)
    }
    return z, nil
}

func main() {
    fmt.Println(Sqrt(0.04))
    fmt.Println(Sqrt(2))
    fmt.Println(Sqrt(4))
    fmt.Println(Sqrt(-2))
}

package main

import (
	"fmt"
	"math"
)

type ErrNegativeSqrt float64

func (e ErrNegativeSqrt) Error() string {
	return fmt.Sprintf("cannot Sqrt negative number: %f", float64(e))
}

func Sqrt(x float64) (float64, error) {
	if x < 0 {
		return 0, ErrNegativeSqrt(x)
	}
	
	prev, z := 0.0, 1.0
	
	for math.Abs(prev - z) > 1e-3 {
		prev = z
		z -= (z*z - x) / (2*z)
	}
	
	return z, nil
}

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