Forked from wuxiao356/Solutions for A Tour of Go Exercises
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January 9, 2017 03:57
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A Tour of Go: Exercises Solution
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| //Exercise: Loops and Functions | |
| package main | |
| import ( | |
| "fmt" | |
| "math" | |
| ) | |
| const delta = 0.000000000001 | |
| func Sqrt(x float64) (value float64, iteration int) { | |
| z := 1.0 | |
| i := 0 | |
| for math.Abs(z*z -x) > delta{ | |
| z = z - (z*z - x)/(z*2) | |
| i++ | |
| } | |
| return z,i | |
| } | |
| func main() { | |
| fmt.Printf("math.Sqrt(2) is %v\n", math.Sqrt(2)) | |
| value, iteration := Sqrt(2) | |
| fmt.Printf("My Sqrt(2) is %v and it takes %v iterations", value, iteration) | |
| } | |
| //Exercise: Slices | |
| package main | |
| import "code.google.com/p/go-tour/pic" | |
| func Pic(dx, dy int) [][]uint8 { | |
| image := make([][]uint8, dy) | |
| for i := range image { | |
| image[i] = make([]uint8, dx) | |
| for j := range image[i] { | |
| image[i][j] = uint8(i*i + j*j) | |
| } | |
| } | |
| return image | |
| } | |
| func main() { | |
| pic.Show(Pic) | |
| } | |
| //Exercise: Maps | |
| package main | |
| import ( | |
| "code.google.com/p/go-tour/wc" | |
| "strings" | |
| ) | |
| func WordCount(s string) map[string]int { | |
| chuncks := strings.Fields(s) | |
| result := make(map[string]int) | |
| for i:= 0; i < len(chuncks); i++{ | |
| if _, exist := result[chuncks[i]]; !exist{ | |
| result[chuncks[i]] = 1 | |
| }else{ | |
| result[chuncks[i]]++ | |
| } | |
| } | |
| return result | |
| } | |
| func main() { | |
| wc.Test(WordCount) | |
| } | |
| //Exercise: Fibonacci closure | |
| package main | |
| import "fmt" | |
| // fibonacci is a function that returns | |
| // a function that returns an int. | |
| func fibonacci() func() int { | |
| num1, num2, sum := 0, 1, 0 | |
| return func() int{ | |
| sum = num1 + num2 | |
| num1 = num2 | |
| num2 = sum | |
| return num1 | |
| } | |
| } | |
| func main() { | |
| f := fibonacci() | |
| for i := 0; i < 10; i++ { | |
| fmt.Println(f()) | |
| } | |
| } | |
| //Exercise: Stringers | |
| package main | |
| import "fmt" | |
| type IPAddr [4]byte | |
| // TODO: Add a "String() string" method to IPAddr. | |
| func (a IPAddr)String() string{ | |
| return fmt.Sprintf("%v.%v.%v.%v",a[0],a[1],a[2],a[3]) | |
| } | |
| func main() { | |
| addrs := map[string]IPAddr{ | |
| "loopback": {127, 0, 0, 1}, | |
| "googleDNS": {8, 8, 8, 8}, | |
| } | |
| for n, a := range addrs { | |
| fmt.Printf("%v: %v\n", n, a) | |
| } | |
| } | |
| //Exercise: Errors | |
| package main | |
| import ( | |
| "fmt" | |
| "math" | |
| ) | |
| type ErrNegativeSqrt float64 | |
| func (err ErrNegativeSqrt)Error() string{ | |
| return fmt.Sprintf("\"cannot Sqrt negative number: %F\"", err) | |
| } | |
| func Sqrt(x float64) (float64, error) { | |
| z := 1.0 | |
| if x >= 0 { | |
| for math.Abs(z*z - x) > 0.000000000001{ | |
| z = z - (z*z - x)/(z*2) | |
| } | |
| return z, nil | |
| }else{ | |
| return x, ErrNegativeSqrt(x) | |
| } | |
| } | |
| func main() { | |
| fmt.Println(Sqrt(2)) | |
| fmt.Println(Sqrt(-2)) | |
| } | |
| //Exercise: Readers | |
| package main | |
| import "code.google.com/p/go-tour/reader" | |
| type MyReader struct{} | |
| // TODO: Add a Read([]byte) (int, error) method to MyReader. | |
| func (r MyReader)Read(b []byte) (int, error) { | |
| for i := range b { | |
| b[i] = 'A' | |
| } | |
| return len(b),nil | |
| } | |
| func main() { | |
| reader.Validate(MyReader{}) | |
| } | |
| //Exercise: rot13Reader |
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