Tour of go solutions.

diff --git a/tour.go b/tour.go
new file mode 100644 (file)
index 0000000..d2aa46b
--- /dev/null
+++ b/tour.go
@@ -0,0 +1,142 @@
+func myPrint(i interface{}) string {
+       switch v := i.(type) {
+       case fmt.Stringer:
+               return "made by Stringer " + v.String()
+       default:
+               return "a huy ego znait.."
+       }
+}
+
+
+func myPrint(i interface{}) string {
+       switch v := i.(type) {
+       case fmt.Stringer:
+               return "made by Stringer " + v.String()
+       case error:
+               return "Huh, that's an error " + v.Error()
+
+       default:
+               return "a huy ego znait.."
+       }
+}
+
+func Sqrt(x float64) float64 {
+       z := 1.0
+       y := 0.0
+       for i := 0; i < 10 && z != x*x && z != y; i++ {
+               fmt.Println(i, z)
+               y = z
+               z -= (z*z - x) / (2*z)
+       }
+       return z
+}
+
+type ErrNegativeSqrt float64
+
+func (e *ErrNegativeSqrt) Error() string {
+       return fmt.Sprintf("cannot Sqrt negative number: %v", *e)
+}
+
+func Sqrt(x float64) (float64, error) {
+       z := 1.0
+       y := 0.0
+       if x < 0 {
+               return 0, (*ErrNegativeSqrt)(&x)
+       }
+       for i := 0; i < 10 && z != x*x && z != y; i++ {
+               fmt.Println(i, z)
+               y = z
+               z -= (z*z - x) / (2 * z)
+       }
+       return z, nil
+}
+
+type MyReader struct{}
+
+func (r MyReader) Read(p []byte) (int, error) {
+       if len(p) == 0 {
+               return 0, nil
+       }
+       x, y := p[:0], p[:]
+       p[0] = byte('A')
+
+       l := 1
+       for m := 1; l < len(p); l += m {
+               x = x[:len(x)+m]
+               y = y[m:]
+               m = copy(y, x)
+       }
+       return l, nil
+}
+
+
+func (MyReader) Read(b []byte) (int, error) {
+       b[0] = 'A'
+       x := b[:1]
+       y := b[1:]
+       //fmt.Printf("%q\n", x)
+       n := 0
+       //fmt.Printf("x = %d, %v, y = %d, %v\n", len(x), x, len(y), y)
+       for len(y) > 0 {
+               n = copy(y, x)
+               //fmt.Printf("A: %v %v\n", x, y)
+               y = y[n:]
+               x = x[:len(x)+n]
+               //fmt.Printf("%d: x = %d, %v, y = %d, %v\n", n, len(x), x, len(y), y)
+       }
+       //fmt.Printf("%d: x = %d, %v, y = %d, %v\n", n, len(x), x, len(y), y)
+       return len(b), nil
+}
+package main
+
+import (
+       "io"
+       "os"
+       "unicode"
+       "strings"
+)
+
+type rot13Reader struct {
+       r io.Reader
+}
+
+var rot13U string = "NOPQRSTUVWXYZABCDEFGHIJKLM"
+var rot13L string = "nopqrstuvwxyzabcdefghijklm"
+
+func (v rot13Reader) Read(b []byte) (int, error) {
+       n, err := v.r.Read(b)
+       if err != nil { return n, err }
+       for i := 0; i < n; i++ {
+               c := rune(b[i])
+               if !unicode.IsLetter(c) {
+                       continue
+               }
+               if unicode.IsLower(c) {
+                       j := b[i] - 'a'
+                       b[i] = rot13L[j]
+               } else {
+                       j := b[i] - 'A'
+                       b[i] = rot13U[j]
+               }
+
+       }
+       return n, nil
+}
+
+func main() {
+       s := strings.NewReader("Lbh penpxrq gur pbqr!")
+       r := rot13Reader{s}
+       io.Copy(os.Stdout, &r)
+}
+
+func Pic(dx, dy int) (img [][]uint8) {
+       img = make([][]uint8, dy)
+       for y := 0; y < dy; y++ {
+               img[y] = make([]uint8, dx)
+               for x := 0; x < dx; x++ {
+                       img[y][x] = uint8(x*y)
+               }
+       }
+       return
+}
+