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A Tour of Go, my code of exercises
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// Implement fibonacci by using go closure | |
package main | |
import "fmt" | |
func fibonacci() func(int) int { | |
var sum1, sum2 int = 0, 1 | |
return func(x int) int { | |
if x == 0 { | |
return sum1 | |
} | |
if x == 1 { | |
return sum2 | |
} | |
sum1, sum2 = sum2, sum1 + sum2 | |
return sum2 | |
} | |
} | |
func main() { | |
f := fibonacci() | |
for i := 0; i < 10; i++ { | |
fmt.Println(f(i)) | |
} | |
} |
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// Implement and define ServeHTTP methods on a String and Struct. | |
// Register them to handle specific paths in your web server. | |
package main | |
import ( | |
"fmt" | |
"net/http" | |
) | |
type String string | |
type Struct struct { | |
Greeting string | |
Punct string | |
Who string | |
} | |
func (s String) ServeHTTP( | |
w http.ResponseWriter, | |
r *http.Request) { | |
fmt.Fprint(w, s) | |
} | |
func (s *Struct) ServeHTTP( | |
w http.ResponseWriter, | |
r *http.Request) { | |
fmt.Fprint(w, s.Greeting, s.Punct, s.Who) | |
} | |
func main() { | |
// your http.Handle calls here | |
http.Handle("/string", String("I'm a frayed knot.")) | |
http.Handle("/struct", &Struct{"Hello", ":", "Gophers!"}) | |
http.ListenAndServe("localhost:4000", nil) | |
} |
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// Define and implement the image interface | |
package main | |
import ( | |
"code.google.com/p/go-tour/pic" | |
"image" | |
"image/color" | |
) | |
type Image struct { | |
width int | |
height int | |
color uint8 | |
} | |
func (m *Image) ColorModel() color.Model { | |
return color.RGBAModel | |
} | |
func (m *Image) Bounds() image.Rectangle { | |
return image.Rect(0, 0, m.width, m.height) | |
} | |
func (m *Image) At(x, y int) color.Color { | |
return color.RGBA{m.color, m.color, 255, 255} | |
} | |
func main() { | |
m := &Image{50, 50, 100} | |
pic.ShowImage(m) | |
} |
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// As a simple way to play with functions and loops, | |
// implement the square root function using Newton's method. | |
package main | |
import ( | |
"fmt" | |
) | |
func Sqrt(x float64) float64 { | |
z := 1.0 | |
for i := 0; i < 10000000; i++ { | |
z = z - (z * z - x) / 2 * z | |
} | |
return z | |
} | |
func main() { | |
fmt.Println(Sqrt(2)) | |
} |
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// Sqrt should return a non-nil error value when given a negative number, | |
// as it doesn't support complex numbers. | |
package main | |
import ( | |
"fmt" | |
) | |
type ErrNegativeSqrt float64 | |
func (e ErrNegativeSqrt) Error() string { | |
return fmt.Sprintf("cannot Sqrt negative number: %f", float64(e)) | |
} | |
func Sqrt(f float64) (float64, error) { | |
var result float64 | |
var err error | |
if f < 0 { | |
result = f | |
err = ErrNegativeSqrt(f) | |
} else { | |
z := 1.0 | |
for i := 0; i < 10000000; i++ { | |
z = z - (z * z - f) / 2 * z | |
} | |
result = z | |
err = nil | |
} | |
return result, err | |
} | |
func main() { | |
fmt.Println(Sqrt(2)) | |
fmt.Println(Sqrt(-2)) | |
} |
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// Implement a rot13Reader that implements io.Reader and reads from an io.Reader, | |
// modifying the stream by applying the ROT13 substitution cipher to all alphabetical characters. | |
package main | |
import ( | |
"io" | |
"os" | |
"strings" | |
) | |
type rot13Reader struct { | |
r io.Reader | |
} | |
func rot13(c byte) byte { | |
if c >= 'a' && c <= 'm' || c >= 'A' && c <= 'M' { | |
return c + 13 | |
} else if c >= 'n' && c <= 'z' || c >= 'N' && c <= 'Z' { | |
return c - 13 | |
} | |
return c | |
} | |
func (rot *rot13Reader) Read(p []byte) (n int, err error) { | |
n, err = rot.r.Read(p) | |
for i := 0; i < n; i++ { | |
p[i] = rot13(p[i]) | |
} | |
return | |
} | |
func main() { | |
s := strings.NewReader( | |
"Lbh penpxrq gur pbqr!") | |
r := rot13Reader{s} | |
io.Copy(os.Stdout, &r) | |
} |
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