package main
import "fmt"
func main() {
is := []int{1, 2}
fmt.Println(is[2:]) // no panic here - this includes is[2] which is out of bound still no panic
fmt.Println(is[3:]) // but panic here
fmt.Println(is[2]) // panic here which is acceptable
}
在上面提到的程序中,即使我们正在从is [2]到on病房访问元素,并且片中只有2个元素,也没有为is [2:]感到恐慌。为什么会这样?
go spec on slice expressions阐明了切片所用索引的要求:
如果0 <=低<=高<=最大<=最大<= cap(a),则索引在范围内,否则它们超出范围。
关于index expressions,相关要求是:
如果0 <= x
您的切片具有len(a) == cap(a) == 2
。您的三个测试用例是:
low == 2
,等于cap(a)
:范围内low == 3
的cap(a)
:超出范围x == 2
等于len(a)
:超出范围