From: sgf <sgf.dma@gmail.com>
Date: Tue, 21 Jun 2022 21:20:59 +0000 (+0300)
Subject: Tour of go solutions.
X-Git-Url: https://gitweb.sgf-dma.tk/?a=commitdiff_plain;h=0e34fba21c65f112e426b652f8170fab4ab3f94d;p=go.git

Tour of go solutions.
---

diff --git a/tour.go b/tour.go
new file mode 100644
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
+}
+