用 initializer_list 初始化一个数组?
Initializing an array with a initializer_list?
有可能吗?
#include <array>
#include <initializer_list>
struct A
{
A ( std::initializer_list< int > l )
: m_a ( l )
{
}
std::array<int,2> m_a;
};
int main()
{
A a{ 1,2 };
}
但这会导致此错误:
t.cpp: In constructor ‘A::A(std::initializer_list<int>)’:
t.cpp:7:19: error: no matching function for call to ‘std::array<int, 2ul>::array(std::initializer_list<int>&)’
: m_a ( l )
^
t.cpp:7:19: note: candidates are:
In file included from t.cpp:1:0:
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: std::array<int, 2ul>::array()
struct array
^
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: candidate expects 0 arguments, 1 provided
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: constexpr std::array<int, 2ul>::array(const std::array<int, 2ul>&)
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: no known conversion for argument 1 from ‘std::initializer_list<int>’ to ‘const std::array<int, 2ul>&’
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: constexpr std::array<int, 2ul>::array(std::array<int, 2ul>&&)
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: no known conversion for argument 1 from ‘std::initializer_list<int>’ to ‘std::array<int, 2ul>&&’
在这种情况下不是。您可以使用 list-initializer
初始化 array
std::array<int, 2> a{1,2};
但是您不能用 initializer_list
初始化 array
,因为 array
只是一个聚合类型,只有默认构造函数和复制构造函数。
您可以将数组留空,然后将 initializer_list
的内容复制到其中。
有可能吗?
#include <array>
#include <initializer_list>
struct A
{
A ( std::initializer_list< int > l )
: m_a ( l )
{
}
std::array<int,2> m_a;
};
int main()
{
A a{ 1,2 };
}
但这会导致此错误:
t.cpp: In constructor ‘A::A(std::initializer_list<int>)’:
t.cpp:7:19: error: no matching function for call to ‘std::array<int, 2ul>::array(std::initializer_list<int>&)’
: m_a ( l )
^
t.cpp:7:19: note: candidates are:
In file included from t.cpp:1:0:
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: std::array<int, 2ul>::array()
struct array
^
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: candidate expects 0 arguments, 1 provided
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: constexpr std::array<int, 2ul>::array(const std::array<int, 2ul>&)
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: no known conversion for argument 1 from ‘std::initializer_list<int>’ to ‘const std::array<int, 2ul>&’
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: constexpr std::array<int, 2ul>::array(std::array<int, 2ul>&&)
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4/array:81:12: note: no known conversion for argument 1 from ‘std::initializer_list<int>’ to ‘std::array<int, 2ul>&&’
在这种情况下不是。您可以使用 list-initializer
初始化array
std::array<int, 2> a{1,2};
但是您不能用 initializer_list
初始化 array
,因为 array
只是一个聚合类型,只有默认构造函数和复制构造函数。
您可以将数组留空,然后将 initializer_list
的内容复制到其中。