Add Chapter 2: Go Basics - Variables, Types, and Flow Control (Deep Dive)

chapters/chapter-2/go.mod

@@ -0,0 +1,3 @@
+module go-tutorial
+
+go 1.21

chapters/chapter-2/main.go

@@ -0,0 +1,241 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"strings"
+)
+
+// 2.1 变量声明示例
+func variableDeclaration() {
+	fmt.Println("=== 变量声明示例 ===")
+	
+	// 1. 显式类型
+	var name string = "Alice"
+	var age int = 25
+	fmt.Printf("name: %s, age: %d\n", name, age)
+	
+	// 2. 类型推断
+	var city = "Beijing"
+	var score = 95.5
+	fmt.Printf("city: %s, score: %.1f\n", city, score)
+	
+	// 3. 短声明
+	x, y, z := 1, 2, 3
+	fmt.Printf("x: %d, y: %d, z: %d\n", x, y, z)
+	
+	// 4. 多变量声明
+	var (
+		pi     = 3.14159
+		euler  = 2.71828
+		golden = 1.61803
+	)
+	fmt.Printf("pi: %.5f, e: %.5f, golden: %.5f\n", pi, euler, golden)
+}
+
+// 2.2 零值示例
+func zeroValues() {
+	fmt.Println("\n=== 零值示例 ===")
+	
+	var intVar int
+	var floatVar float64
+	var boolVar bool
+	var stringVar string
+	var ptrVar *int
+	
+	fmt.Printf("int: %d\n", intVar)
+	fmt.Printf("float: %f\n", floatVar)
+	fmt.Printf("bool: %v\n", boolVar)
+	fmt.Printf("string: '%s'\n", stringVar)
+	fmt.Printf("ptr: %v\n", ptrVar)
+	
+	// 结构体零值
+	type User struct {
+		Name  string
+		Age   int
+		Email string
+	}
+	u := User{}
+	fmt.Printf("User: %+v\n", u)
+}
+
+// 2.3 数据类型示例
+func dataTypes() {
+	fmt.Println("\n=== 数据类型示例 ===")
+	
+	// 整型
+	var i8 int8 = 127
+	var i64 int64 = 9223372036854775807
+	fmt.Printf("int8: %d, int64: %d\n", i8, i64)
+	
+	// byte 和 rune
+	var b byte = 'A'
+	var r rune = '中'
+	fmt.Printf("byte: %c (%d), rune: %c (%d)\n", b, b, r, r)
+	
+	// 浮点数精度问题
+	a := 0.1 + 0.2
+	b := 0.3
+	fmt.Printf("0.1 + 0.2 == 0.3: %v\n", a == b)
+	fmt.Printf("0.1 + 0.2 = %.20f\n", a)
+	
+	// 字符串
+	s := "Hello 世界"
+	fmt.Printf("字符串: %s\n", s)
+	fmt.Printf("字节数: %d\n", len(s))
+	
+	// 遍历字符串
+	fmt.Print("字符遍历: ")
+	for i, r := range s {
+		fmt.Printf("[%d]%c ", i, r)
+	}
+	fmt.Println()
+}
+
+// 2.4 类型转换示例
+func typeConversion() {
+	fmt.Println("\n=== 类型转换示例 ===")
+	
+	var f float64 = 3.14159
+	var i int = int(f)  // 截断
+	fmt.Printf("float64(3.14159) -> int: %d\n", i)
+	
+	// 四舍五入
+	i = int(math.Round(f))
+	fmt.Printf("round(3.14159): %d\n", i)
+	
+	// 字符串转数字
+	numStr := "42"
+	num, _ := strconv.Atoi(numStr)
+	fmt.Printf("字符串 '%s' -> 数字: %d\n", numStr, num)
+}
+
+// 2.5 运算符示例
+func operators() {
+	fmt.Println("\n=== 运算符示例 ===")
+	
+	a, b := 10, 3
+	
+	// 算术运算
+	fmt.Printf("%d + %d = %d\n", a, b, a+b)
+	fmt.Printf("%d / %d = %d (整数除法)\n", a, b, a/b)
+	fmt.Printf("%d / %d = %.2f (浮点除法)\n", a, b, float64(a)/float64(b))
+	
+	// 位运算
+	x, y := 6, 3  // 110, 011
+	fmt.Printf("%d & %d = %d\n", x, y, x&y)
+	fmt.Printf("%d | %d = %d\n", x, y, x|y)
+	fmt.Printf("%d ^ %d = %d\n", x, y, x^y)
+	fmt.Printf("%d << 1 = %d\n", x, x<<1)
+}
+
+// 2.6 流程控制示例
+func flowControl() {
+	fmt.Println("\n=== 流程控制示例 ===")
+	
+	// if-else
+	score := 85
+	if score >= 90 {
+		fmt.Println("优秀")
+	} else if score >= 80 {
+		fmt.Println("良好")
+	} else {
+		fmt.Println("及格")
+	}
+	
+	// switch
+	day := 3
+	switch day {
+	case 1, 2, 3, 4, 5:
+		fmt.Println("工作日")
+	case 6, 7:
+		fmt.Println("周末")
+	default:
+		fmt.Println("无效日期")
+	}
+	
+	// for 循环
+	fmt.Print("for 循环: ")
+	for i := 0; i < 5; i++ {
+		fmt.Printf("%d ", i)
+	}
+	fmt.Println()
+	
+	// range 遍历
+	slice := []int{10, 20, 30, 40, 50}
+	fmt.Print("range 遍历: ")
+	for i, v := range slice {
+		fmt.Printf("[%d]=%d ", i, v)
+	}
+	fmt.Println()
+}
+
+// 2.7 综合案例：计算器
+func calculator() {
+	fmt.Println("\n=== 简易计算器 ===")
+	
+	num1 := 10.5
+	num2 := 3.2
+	operators := []string{"+", "-", "*", "/"}
+	
+	for _, op := range operators {
+		var result float64
+		switch op {
+		case "+":
+			result = num1 + num2
+		case "-":
+			result = num1 - num2
+		case "*":
+			result = num1 * num2
+		case "/":
+			result = num1 / num2
+		}
+		fmt.Printf("%.1f %s %.1f = %.2f\n", num1, op, num2, result)
+	}
+}
+
+// 2.7 综合案例：素数判断
+func primeNumbers() {
+	fmt.Println("\n=== 素数统计 ===")
+	
+	count := 0
+	for i := 2; i <= 100; i++ {
+		if isPrime(i) {
+			fmt.Printf("%d ", i)
+			count++
+			if count%10 == 0 {
+				fmt.Println()
+			}
+		}
+	}
+	fmt.Printf("\n1-100 共有 %d 个素数\n", count)
+}
+
+func isPrime(n int) bool {
+	if n <= 1 {
+		return false
+	}
+	if n == 2 {
+		return true
+	}
+	if n%2 == 0 {
+		return false
+	}
+	for i := 3; i*i <= n; i += 2 {
+		if n%i == 0 {
+			return false
+		}
+	}
+	return true
+}
+
+func main() {
+	variableDeclaration()
+	zeroValues()
+	dataTypes()
+	typeConversion()
+	operators()
+	flowControl()
+	calculator()
+	primeNumbers()
+}