go学习1

 1 package main

 2 

 3 import (

 4     "bufio"

 5     "fmt"

 6     "math"

 7     "os"

 8     "runtime"

 9 )

10 

11 const result = "Polar radius=%.02f θ=%.02f° → Cartesian x=%.02f y=%.02f\n"

12 

13 var prompt = "Enter a radius and an angle (in degrees), e.g., 12.5 90, " +

14         "or %s to quit."

15 

16 type polar struct {

17     radius float64

18     θ      float64

19 }

20 

21 type cartesian struct {

22     x   float64

23     y   float64

24 }

25 

26 func init() {

27     if runtime.GOOS == "windows" {

28         prompt = fmt.Sprintf(prompt, "Ctrl+Z, Enter")

29     } else { // Unix-like

30         prompt = fmt.Sprintf(prompt, "Ctrl+D")

31     }

32 }

33 

34 func main() {

35     questions := make(chan polar)

36     defer close(questions)

37     answers := createSolver(questions)

38     defer close(answers)

39     interact(questions, answers)

40 }

41 

42 func createSolver(questions chan polar) chan cartesian {

43     answers := make(chan cartesian)

44     go func() {

45         for {

46             polarCoord := <-questions

47             θ := polarCoord.θ * math.Pi / 180.0 // degrees to radians

48             x := polarCoord.radius * math.Cos(θ)

49             y := polarCoord.radius * math.Sin(θ)

50             answers <- cartesian{x, y}

51         }

52     }()

53     return answers

54 }

55 

56 func interact(questions chan polar, answers chan cartesian) {

57     reader := bufio.NewReader(os.Stdin)

58     fmt.Println(prompt)

59     for {

60         fmt.Printf("Radius and angle: ")

61         line, err := reader.ReadString('\n')

62         if err != nil {

63             break

64         }

65         var radius, θ float64

66         if _, err := fmt.Sscanf(line, "%f %f", &radius, &θ); err != nil {

67             fmt.Fprintln(os.Stderr, "invalid input")

68             continue

69         }

70         questions <- polar{radius, θ}

71         coord := <-answers

72         fmt.Printf(result, radius, θ, coord.x, coord.y)

73     }

74     fmt.Println()

75 }