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 }

 

posted @ 2015-01-11 07:33  Kulle  Views(188)  Comments(0)    收藏  举报