| // Copyright 2012 The Go Authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style | |
| // license that can be found in the LICENSE file. | |
| package main | |
| import ( | |
| "fmt" | |
| "math" | |
| ) | |
| type ErrNegativeSqrt float64 | |
| func (e ErrNegativeSqrt) Error() string { | |
| return fmt.Sprintf("Sqrt: negative number %g", e) | |
| } | |
| const delta = 1e-10 | |
| func Sqrt(f float64) (float64, error) { | |
| if f < 0 { | |
| return 0, ErrNegativeSqrt(f) | |
| } | |
| z := f | |
| for { | |
| n := z - (z*z-f)/(2*z) | |
| if math.Abs(n-z) < delta { | |
| break | |
| } | |
| z = n | |
| } | |
| return z, nil | |
| } | |
| func main() { | |
| fmt.Println(Sqrt(2)) | |
| fmt.Println(Sqrt(-2)) | |
| } |