Initial commit - learning the basics

tour_of_go/l4/2

@@ -0,0 +1,39 @@
+package main
+
+import "fmt"
+
+func main() {
+	var aa [2]string
+
+	aa[0] = "Hello"
+	aa[1] = "World"
+	fmt.Println(aa[0], aa[1])
+	fmt.Println(aa)
+
+	primes := [6]int{2, 3, 5, 7, 11, 13}
+	fmt.Println(primes)
+
+	var s []int = primes[1:4]
+	fmt.Printf("The primes are %d and the slice is %d", primes, s)
+
+	// Slices are references to array sections
+	// Changing elements in a slice results in changes to the array
+	// So other slices referencing the same array section will also be changed
+
+	names := [4]string{
+		"John",
+		"Paul",
+		"George",
+		"Ringo",
+	}
+	fmt.Println(names)
+
+	a := names[0:2]
+	b := names[1:3]
+	fmt.Println(a, b)
+
+	// Now make some changes
+	b[0] = "XXX"
+	fmt.Println(a, b)
+	fmt.Println(names)
+}

tour_of_go/l4/append.go

@@ -0,0 +1,23 @@
+package main
+
+import "fmt"
+
+func printSlice(s []int) {
+	fmt.Printf("len=%d cap=%d %v\n", len(s), cap(s), s)
+}
+func main() {
+	var s []int
+	printSlice(s)
+
+	s = append(s, 0)
+	printSlice(s)
+
+	s = append(s, 1)
+	printSlice(s)
+
+	s = append(s, 2, 3, 4)
+	printSlice(s)
+
+	s = append(s, 56)
+	printSlice(s)
+}

tour_of_go/l4/arrays.go

@@ -0,0 +1,72 @@
+package main
+
+import "fmt"
+
+func main() {
+	var aa [2]string
+
+	aa[0] = "Hello"
+	aa[1] = "World"
+	fmt.Println(aa[0], aa[1])
+	fmt.Println(aa)
+
+	primes := [6]int{2, 3, 5, 7, 11, 13}
+	fmt.Println(primes)
+
+	var s []int = primes[1:4]
+	fmt.Printf("The primes are %d and the slice is %d", primes, s)
+
+	// Slices are references to array sections
+	// Changing elements in a slice results in changes to the array
+	// So other slices referencing the same array section will also be changed
+
+	names := [4]string{
+		"John",
+		"Paul",
+		"George",
+		"Ringo",
+	}
+	fmt.Println(names)
+
+	a := names[0:2]
+	b := names[1:3]
+	fmt.Println(a, b)
+
+	// Now make some changes
+	b[0] = "XXX"
+	fmt.Println(a, b)
+	fmt.Println(names)
+
+	// Slice literals - like array literals, but without the length
+	q := []int{2, 3, 5, 7, 11, 13}
+	fmt.Println(q)
+
+	r := []bool{true, false, true, true, false, true}
+	fmt.Println(r)
+
+	sx := []struct {
+		i int
+		b bool
+	}{
+		{2, true},
+		{3, false},
+		{5, true},
+		{7, true},
+		{11, false},
+		{13, true},
+	}
+	fmt.Println(sx)
+
+	// Slice defaults
+
+	ss := []int{2, 3, 5, 7, 11, 13}
+
+	ss = ss[1: 4]
+	fmt.Println(ss)
+
+	ss = ss[:2]
+	fmt.Println(ss)
+
+	ss = ss[1:]
+	fmt.Println(ss)
+}

tour_of_go/l4/making-slices.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+func printSlice(s []int) {
+	fmt.Printf("len=%d cap=%d %v\n", len(s), cap(s), s)
+}
+
+func main() {
+	a := make([]int, 5)
+	printSlice(a)
+
+	b := make([]int, 0, 5)
+	printSlice(b)
+
+	c := b[:2]
+	printSlice(c)
+
+	d := c[2:5]
+	printSlice(d)
+
+	// Slices can contain any type including other slices
+	board := [][]string{
+		[]string{"_", "_", "_"},
+		[]string{"_", "_", "_"},
+		[]string{"_", "_", "_"},
+	}
+
+	board[0][0] = "X"
+	board[2][2] = "O"
+	board[1][2] = "X"
+	board[1][0] = "O"
+	board[0][2] = "X"
+
+	for i := 0; i < len(board); i++ {
+		fmt.Printf("%s\n", strings.Join(board[i], " "))
+	}
+}

tour_of_go/l4/pointers.go

@@ -0,0 +1,18 @@
+package main
+
+import "fmt"
+
+func main() {
+	i, j := 42, 2701
+
+	p := &i
+	fmt.Println(*p)
+	*p = 21
+	fmt.Println(i)
+
+	p = &j
+	*p = *p / 37
+	fmt.Println(j)
+
+	fmt.Println(i, j)
+}

tour_of_go/l4/range.go

@@ -0,0 +1,21 @@
+package main
+
+import "fmt"
+
+var pow = []int{1, 2, 4, 8, 16, 32, 64, 128}
+
+func main() {
+	for i, v := range pow {
+		fmt.Printf("2**%d = %d\n", i, v)
+	}
+
+	// You can skip the index by assigning it to "_"
+	// Or you can skip the value by omitting the 2nd value -> "for i := range XXX"
+	new_pow := make([]int, 10)
+	for i := range new_pow {
+		new_pow[i] = 1 << uint(i)
+	}
+	for _, value := range new_pow {
+		fmt.Printf("%d\n", value)
+	}
+}

tour_of_go/l4/slices-cont.go

@@ -0,0 +1,33 @@
+package main
+
+import "fmt"
+
+func printSlice(s []int) {
+	fmt.Printf("len=%d cap=%d %v\n", len(s), cap(s), s)
+}
+
+func main() {
+	s := []int{2, 3, 5, 7, 11, 13}
+	printSlice(s)
+
+	s = s[:0]
+	printSlice(s)
+
+	s = s[:4]
+	printSlice(s)
+
+	s = s[2:]
+	printSlice(s)
+
+	// Extend beyond capacity
+	// s = s[:10]
+	// printSlice(s)
+
+	// Zero value of a slice is nil
+	var ns []int
+	printSlice(ns)
+
+	if ns == nil {
+		fmt.Println("nil!!")
+	}
+}

tour_of_go/l4/structs.go

@@ -0,0 +1,27 @@
+package main
+
+import "fmt"
+
+type Vertex struct {
+	X int
+	Y int
+}
+
+var (
+	v1 = Vertex{1, 2}
+	v2 = Vertex{X: 1}
+	v3 = Vertex{}
+	p = &Vertex{1, 2}
+)
+
+func main() {
+	v := Vertex{1, 2}
+	v.X = 4
+	fmt.Println(v)
+
+	o := &v
+	o.X = 12
+	fmt.Printf("New vertex value is %d\n", v)
+
+	fmt.Println(v1, p, v2, v3)
+}