[英]How to emplace to a std::vector of std::array?
With a vector of vectors, I can do this:使用向量向量,我可以这样做:
std::vector<std::vector<int>> vov;
vov.emplace_back(std::initializer_list<int>{0, 0});
However, the equivalent fails for the vector of std::array:但是,对于 std::array 的向量,等效失败:
std::vector<std::array<int, 2>> voa;
voa.emplace_back(std::initializer_list<int>{0,0});
What is the correct way to emplace an array inside vector?在向量中放置数组的正确方法是什么?
Edit:编辑:
Yes, you can create std::array from
initializer list
:是的,您可以从
初始化列表
创建 std::array :
std::array<int, 2> a = {0, 0}
works fine.工作正常。
The error:错误:
error C2664: 'std::array<int,2>::array(const std::array<int,2> &)': cannot convert argument 1 from 'std::initializer_list<int>' to 'const std::array<int,2> &'
std::array
doesn't have any constructors, it's initialization follows aggregate initialization. std::array
没有任何构造函数,它的初始化遵循聚合初始化。
You have two options, either use push_back
instead of emplace_back
with a brace-init-list:您有两个选择,要么使用
push_back
而不是emplace_back
和大括号初始化列表:
voa.push_back({ 0, 0 });
Or you can use std::array
's (implicit) copy and move constructors and construct a temporary std::array
:或者您可以使用
std::array
的(隐式)复制和移动构造函数并构造一个临时std::array
:
voa.emplace_back(std::array<int>{0, 0}); // pre C++17
voa.emplace_back(std::array{0, 0}); // C++17
Ultimately both methods should generate the same machine code.最终,这两种方法都应该生成相同的机器代码。
In response to your edit:回应您的编辑:
std::array<int, 2> a = {0, 0};
is NOT the same as不一样
std::array<int, 2> a = std::initializer_list<int>{0, 0};
{0, 0}
is a brace-init-list , which doesn't have a type. {0, 0}
是一个没有类型的大括号初始化列表。 This is why you can't use them as an argument to a templated function.这就是为什么您不能将它们用作模板化 function 的参数。 See this question for more details.
有关更多详细信息,请参阅此问题。
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