slice

slice的本質是一個三元組(陣列地址，長度，容量)

一個例子

package main

import (
	"fmt"
)


func test(input []int) []int{
	// input: 0x40c110->{address, 4, 4}
	fmt.Printf("Slice inside address: %p\n", &input)
	// input: 0x40c110->{address, 4, 4}，但對address的修改影響到了val:0x40c0e0->{address, 4, 4}
	input[0] = -1
	input =
 
 append(input, 5)
	// input: 0x40c110->{address, 5, 8}，但val仍然為0x40c0e0->{address, 4, 4}
	fmt.Println(input, len(input), cap(input))
	return input
}

func main() {
	// val：0x40c0e0->{address, 4, 4}
	val := []int{1, 2, 3, 4}
	fmt.Printf("Slice outside address: %p\n", &val)
	fmt.Println(val, len(val), cap
 
(val))
	copyVal := test(val)
	fmt.Printf("Slice outside address: %p\n", &val)
	fmt.Println(val, len(val), cap(val))
	fmt.Printf("CopySlice address: %p\n", &copyVal)
	fmt.Println(copyVal, len(copyVal), cap(copyVal))
}

結果：

Slice outside address: 0x40c0e0
[1 2 3 4] 4 4
Slice inside address: 0x40c110
[-1 2 3 4 5] 5 8
Slice outside address: 0x40c0e0
[-1 2 3 4] 4 4
CopySlice address: 0x40c100
[-1 2 3 4 5] 5 8

 

結論：
傳入的是slice三元組的值拷貝，返回的slice三元組值拷貝給外部變數