有一个名为 Matrix
的结构,它有一个模板参数 N
和 data_
字段:
#include <cstddef>
#include <vector>
template <std::size_t N>
struct Matrix {
std::vector<std::vector<int>> data_{N, std::vector<int>(N)};
};
为什么不能使用圆括号初始化data_
?
std::vector<std::vector<int>> data_(N, std::vector<int>(N));
这是错误:
<source>:6:41: error: unknown type name 'N'
std::vector<std::vector<int>> data_(N, std::vector<int>(N));
^
<source>:6:61: error: declaration of 'N' shadows template parameter
std::vector<std::vector<int>> data_(N, std::vector<int>(N));
^
<source>:4:23: note: template parameter is declared here
template <std::size_t N>
最佳答案
Default member initializer (C++11 起)不支持圆括号初始化器,只支持花括号初始化器和等号初始化器。
Through a default member initializer, which is a brace or equals initializer included in the member declaration and is used if the member is omitted from the member initializer list of a constructor.
除了你已经展示的支撑之外,你还可以
template <std::size_t N>
struct Matrix {
std::vector<std::vector<int>> data_ = std::vector<std::vector<int>>(N, std::vector<int>(N));
};
https://stackoverflow.com/questions/65458163/