-
-
Save ursuad/2182e0c3e0c82c47aed8beee86a6d9fd to your computer and use it in GitHub Desktop.
tour.golang exercise solutions
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| /* Exercise: Loops and Functions #43 ×/ | |
| package main | |
| import ( | |
| "fmt" | |
| "math" | |
| ) | |
| func Sqrt(x float64) float64 { | |
| z := float64(2.) | |
| s := float64(0) | |
| for { | |
| z = z - (z*z - x)/(2*z) | |
| if math.Abs(s-z) < 1e-15 { | |
| break | |
| } | |
| s = z | |
| } | |
| return s | |
| } | |
| func main() { | |
| fmt.Println(Sqrt(2)) | |
| fmt.Println(math.Sqrt(2)) | |
| } | |
| /******************************************************************************************************/ | |
| /* Exercise: Maps #44 */ | |
| package main | |
| import ( | |
| "tour/wc" | |
| "strings" | |
| ) | |
| func WordCount(s string) map[string]int { | |
| ss := strings.Fields(s) | |
| num := len(ss) | |
| ret := make(map[string]int) | |
| for i := 0; i < num; i++ { | |
| (ret[ss[i]])++ | |
| } | |
| return ret | |
| } | |
| func main() { | |
| wc.Test(WordCount) | |
| } | |
| /******************************************************************************************************/ | |
| /* Exercise: Slices #45 */ | |
| package main | |
| import "tour/pic" | |
| func Pic(dx, dy int) [][]uint8 { | |
| ret := make([][]uint8, dy) | |
| for i := 0; i < dy; i++ { | |
| ret[i] = make([]uint8, dx) | |
| for j := 0; j < dx; j++ { | |
| ret[i][j] = uint8(i^j+(i+j)/2) | |
| } | |
| } | |
| return ret | |
| } | |
| func main() { | |
| pic.Show(Pic) | |
| } | |
| /******************************************************************************************************/ | |
| /* Exercise: Fibonacci closure #46 */ | |
| package main | |
| import "fmt" | |
| // fibonacci is a function that returns | |
| // a function that returns an int. | |
| func fibonacci() func() int { | |
| sum := 1 | |
| prev := 0 | |
| return func() int { | |
| old := sum | |
| sum += prev | |
| prev = old | |
| return sum | |
| } | |
| } | |
| func main() { | |
| f := fibonacci() | |
| for i := 0; i < 10; i++ { | |
| fmt.Println(f()) | |
| } | |
| } | |
| /******************************************************************************************************/ | |
| /* Advanced Exercise: Complex cube roots #47 */ | |
| package main | |
| import ( | |
| "fmt" | |
| "math/cmplx" | |
| ) | |
| func Cbrt(x complex128) complex128 { | |
| z := complex128(2) | |
| s := complex128(0) | |
| for { | |
| z = z - (cmplx.Pow(z,3) - x)/(3 * (z * z)) | |
| if cmplx.Abs(s-z) < 1e-17 { | |
| break | |
| } | |
| s = z | |
| } | |
| return z | |
| } | |
| func main() { | |
| fmt.Println(Cbrt(2)) | |
| } | |
| /******************************************************************************************************/ | |
| /* Exercise: Errors #57 */ | |
| package main | |
| import ( | |
| "fmt" | |
| ) | |
| type ErrNegativeSqrt float64 | |
| func (e ErrNegativeSqrt) Error() string { | |
| return fmt.Sprintf("cannot Sqrt negativ number: %g", float64(e)) | |
| } | |
| func Sqrt(f float64) (float64, error) { | |
| if f < 0 { | |
| return 0, ErrNegativeSqrt(f) | |
| } | |
| return 0, nil | |
| } | |
| func main() { | |
| fmt.Println(Sqrt(2)) | |
| fmt.Println(Sqrt(-2)) | |
| } | |
| /******************************************************************************************************/ |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment