在＆QUOT;帽QUOT; Golang的 [英] The "cap" of Golang

问题描述

下面去$​​ C $ C：

The following go code:

var numbers4 = [...]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
slice := numbers4[4:6:8] 
fmt.Printf("%d\n", cap(slice))

为什么帽（片）等于 4 ？

我曾经以为这应该是 2 。

推荐答案

numbers4 [4：6：8] 是的整片前pression ：

有关的阵列，指针阵列，或切片 A （但不是一个串），主前pression

For an array, pointer to array, or slice a (but not a string), the primary expression

a[low : high : max]

  
  

构造相同类型的片，并与相同长度和元素的简单的片前pression A [低：高] 。此外，它的将其设置为最大控制所产生的切片的能力 - 低

constructs a slice of the same type, and with the same length and elements as the simple slice expression a[low : high]. Additionally, it controls the resulting slice's capacity by setting it to max - low.

该规范说，整片前pression控制能力，限制了最大 - 低，而你的情况是 8 - 4 = 4

The spec says the full slice expression controls the capacity, limiting it to max - low, which in your case is 8 - 4 = 4.

的容量的不可以额外的切片可以延长元素，容量最大长度为这片可以延长，其中包括当前长度+超越了多余的元素长度。

The capacity is not the "extra" elements of which the slice may be extended, the capacity is the max length to which a slice may be extended, which includes current length + extra elements beyond the length.

slice := numbers4[4:6:8]

len(slice) = 6 - 4 = 2
cap(slice) = 8 - 4 = 4

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