去子串操作，没有索引越界？

Question

我想知道为什么第二个 fmt.Println 中的“s[1:]”没有抛出索引超出范围错误？索引 1 明显超出范围

package main

import "fmt"

func main() {

   s := "J"

   //fmt.Println(s[1]) // This results in a runtime error: index out of range

   fmt.Println(s[1:]) // Why does this work? Index value 1 is clearly out of range, but the statement prints an empty string

}

Answer 1

作为language specification状态，给定 slice 表达式

a[low : high]

For arrays or strings, the indices are in range if 0 <= low <= high <= len(a), otherwise they are out of range. [...] If the indices are out of range at run time, a run-time panic occurs.

在你的例子中

s[1:]

low是1 , high是len(s)和 len(s)是1 .自 low <= len(s) ，没有 panic 。