Exercise: Errors

Copy your Sqrt function from the earlier exercise 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 

  1. type ErrNegativeSqrt float64

and make it an error by giving it a 

  1. func (e ErrNegativeSqrt) Error() string

method such that ErrNegativeSqrt(-2).Error() returns "cannot Sqrt negative number: -2".

Note: A call to fmt.Sprint(e) inside the Error method will send the program into an infinite loop. You can avoid this by converting e first: fmt.Sprint(float64(e)). Why?

Change your Sqrt function to return an ErrNegativeSqrt value when given a negative number.

exercise-errors.go

  1. package main
  3. import (
  4.     "fmt"
  5. )
  7. func Sqrt(x float64) (float64, error) {
  8.     return 0, nil
  9. }
  11. func main() {
  12.     fmt.Println(Sqrt(2))
  13.     fmt.Println(Sqrt(-2))
  14. }