Go语言切片传递机制解析：s[:]的正确用法与误区

package main

import "fmt"

func modifySlice(s []int) {
    if len(s) > 0 {
        s[0] = 99 // 修改切片元素会影响原始底层数组
    }
    s = append(s, 100) // append操作可能导致底层数组重新分配，不影响原始切片头
    fmt.Println("Inside modifySlice:", s)
}

func main() {
    mySlice := []int{1, 2, 3}
    fmt.Println("Original slice before:", mySlice) // Output: [1 2 3]

    modifySlice(mySlice)
    fmt.Println("Original slice after:", mySlice)  // Output: [99 2 3] (第一个元素被修改)
}

package main

import "fmt"

func main() {
    // 定义一个数组
    myArray := [5]int{10, 20, 30, 40, 50}
    fmt.Println("Array:", myArray)

    // 使用 myArray[:] 从数组创建切片，引用整个数组
    mySlice := myArray[:]
    fmt.Println("Slice from array:", mySlice) // Output: [10 20 30 40 50]

    // 也可以创建子切片
    subSlice := myArray[1:4] // 从索引1到索引3的元素
    fmt.Println("Sub-slice from array:", subSlice) // Output: [20 30 40]

    // 修改切片元素会影响原始数组
    mySlice[0] = 100
    fmt.Println("Array after slice modification:", myArray) // Output: [100 20 30 40 50]
}

package main

import "fmt"

func processSlice(s []int) {
    fmt.Printf("Inside processSlice: %v, Length: %d, Capacity: %d\n", s, len(s), cap(s))
    if len(s) > 0 {
        s[0] = 999
    }
}

func main() {
    mySlice := []int{1, 2, 3, 4, 5}
    fmt.Printf("Original slice before calls: %v, Length: %d, Capacity: %d\n", mySlice, len(mySlice), cap(mySlice))

    fmt.Println("\n--- Calling with method(s) ---")
    processSlice(mySlice)
    fmt.Printf("Original slice after method(s): %v, Length: %d, Capacity: %d\n", mySlice, len(mySlice), cap(mySlice))

    // Reset mySlice for the next test
    mySlice = []int{1, 2, 3, 4, 5}
    fmt.Printf("\nOriginal slice (reset) before method(s[:]): %v, Length: %d, Capacity: %d\n", mySlice, len(mySlice), cap(mySlice))

    fmt.Println("\n--- Calling with method(s[:]) ---")
    processSlice(mySlice[:]) // mySlice[:] 在这里是冗余的
    fmt.Printf("Original slice after method(s[:]): %v, Length: %d, Capacity: %d\n", mySlice, len(mySlice), cap(mySlice))
}