我按照以下示例 tour.golang/moretypes/10 我修改了希望得到相同结果的代码。我没有。这是一个错误还是文档错误？旅游状态
I was following the example tour.golang/moretypes/10 I modified the code expecting to get the same result. I did not. Is this a bug, or a documentation error? The tour states
一个零切片的长度和容量为0
A nil slice has a length and capacity of 0.
我的y变量的长度和容量都是0.
My y variable has a length and capacity of 0.
package main import "fmt" func myPrint(z []int) { fmt.Println(z, len(z), cap(z)) if z == nil { fmt.Println("nil!") } } func main() { var z []int y := []int {} myPrint(z) myPrint(y) }这是我的输出。
[] 0 0 nil! [] 0 0我期待第二个零〜为什么没有我得到了它？
I was expecting a second "nil"~ Why didn't I get it?
推荐答案您引用的doc指出 nil slice的长度和容量均为0 ，但不是每个长度和零容量片都是零片。
The doc you referenced to states that A nil slice has a length and capacity of 0 but not that every slice of length and capacity of zero is a nil slice.
这支持 len 和 cap 指向未指定（nil）的指针（片）。否则，我们需要首先检查非零。
This is a convenience to support len and cap on pointers (of slices) which are unassigned (nil). Otherwise we would need to check for non-nil first.
指针是理解我认为的问题的关键词。在第一种情况下，你有一个零指针，在第二种情况下你已经分配了slice，但它是空的。这可以适用于任何结构：
Pointer is key word here to understand the problem I think. In the first case you have a nil pointer, in the second case you have allocated slice, but it's empty. This would hold for any structure:
package main import "fmt" func main() { var s *struct{} fmt.Println(s) // <nil> s = &struct{}{} fmt.Println(s) // &{} }更多推荐
切片的零值不是零
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