mirror of
https://github.com/gopl-zh/gopl-zh.github.com.git
synced 2024-12-26 23:06:20 +00:00
80 lines
1.5 KiB
Go
80 lines
1.5 KiB
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
|
|
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
|
|
|
|
// See page 88.
|
|
|
|
// Append illustrates the behavior of the built-in append function.
|
|
package main
|
|
|
|
import "fmt"
|
|
|
|
func appendslice(x []int, y ...int) []int {
|
|
var z []int
|
|
zlen := len(x) + len(y)
|
|
if zlen <= cap(x) {
|
|
// There is room to expand the slice.
|
|
z = x[:zlen]
|
|
} else {
|
|
// There is insufficient space.
|
|
// Grow by doubling, for amortized linear complexity.
|
|
zcap := zlen
|
|
if zcap < 2*len(x) {
|
|
zcap = 2 * len(x)
|
|
}
|
|
z = make([]int, zlen, zcap)
|
|
copy(z, x)
|
|
}
|
|
copy(z[len(x):], y)
|
|
return z
|
|
}
|
|
|
|
//!+append
|
|
func appendInt(x []int, y int) []int {
|
|
var z []int
|
|
zlen := len(x) + 1
|
|
if zlen <= cap(x) {
|
|
// There is room to grow. Extend the slice.
|
|
z = x[:zlen]
|
|
} else {
|
|
// There is insufficient space. Allocate a new array.
|
|
// Grow by doubling, for amortized linear complexity.
|
|
zcap := zlen
|
|
if zcap < 2*len(x) {
|
|
zcap = 2 * len(x)
|
|
}
|
|
z = make([]int, zlen, zcap)
|
|
copy(z, x) // a built-in function; see text
|
|
}
|
|
z[len(x)] = y
|
|
return z
|
|
}
|
|
|
|
//!-append
|
|
|
|
//!+growth
|
|
func main() {
|
|
var x, y []int
|
|
for i := 0; i < 10; i++ {
|
|
y = appendInt(x, i)
|
|
fmt.Printf("%d cap=%d\t%v\n", i, cap(y), y)
|
|
x = y
|
|
}
|
|
}
|
|
|
|
//!-growth
|
|
|
|
/*
|
|
//!+output
|
|
0 cap=1 [0]
|
|
1 cap=2 [0 1]
|
|
2 cap=4 [0 1 2]
|
|
3 cap=4 [0 1 2 3]
|
|
4 cap=8 [0 1 2 3 4]
|
|
5 cap=8 [0 1 2 3 4 5]
|
|
6 cap=8 [0 1 2 3 4 5 6]
|
|
7 cap=8 [0 1 2 3 4 5 6 7]
|
|
8 cap=16 [0 1 2 3 4 5 6 7 8]
|
|
9 cap=16 [0 1 2 3 4 5 6 7 8 9]
|
|
//!-output
|
|
*/
|