如何初始化向量的向量的 std::map？

Question

我正在处理非常复杂的程序，我需要初始化 std::map 类型的变量std::map<int, std::vector<std::vector<std::array<std::byte, 2>>>>作为 const 变量稍后进行一些比较。 我试着这样做：

const std::vector<std::vector<std::array<std::byte, 2>>>
        boundaries_length_one = {{{std::byte('\x00'), std::byte('\x7f')}}};
const std::vector<std::vector<std::array<std::byte, 2>>>
        boundaries_length_two = {{{std::byte('\xc2'), std::byte('\xdf')}, {std::byte('\x80'), std::byte('\xbf')}}};
const std::vector<std::vector<std::array<std::byte, 2>>> boundaries_length_three = {
        {{std::byte('\xe0'), nullptr}, {std::byte('\xa0'), std::byte('\xbf')}, {std::byte('\x80'), std::byte('\xbf')}},
        {{std::byte('\xe1'), std::byte('\xec')}, {std::byte('\x80'), std::byte('\xbf')},
         {std::byte('\x80'), std::byte('\xbf')}},
        {{std::byte('\xe0'), nullptr}, {std::byte('\x80'), std::byte('\x9f')}, {std::byte('\x80'), std::byte('\xbf')}},
        {{std::byte('\xee'), std::byte('\xef')}, {std::byte('\x80'), std::byte('\xbf')},
         {std::byte('\x80'), std::byte('\xbf')}}
};
const std::vector<std::vector<std::array<std::byte, 2>>> boundaries_length_four = {
        {{std::byte('\xf0'), nullptr}, {std::byte('\x90'), std::byte('\xbf')}, {std::byte('\x80'), std::byte('\xbf')},
         {std::byte('\x80'), std::byte('\xbf')}},
        {{std::byte('\xf1'), std::byte('\xf3')}, {std::byte('\x80'), std::byte('\xbf')},
         {std::byte('\x80'), std::byte('\xbf')}, {std::byte('\x80'), std::byte('\xbf')}},
        {{std::byte('\xf4'), nullptr}, {std::byte('\x80'), std::byte('\x8f')}, {std::byte('\x80'), std::byte('\xbf')},
         {std::byte('\x80'), std::byte('\xbf')}}
};
std::map<int, const std::vector<std::vector<std::array<std::byte, 2>>>> boundaries = {
        {1, boundaries_length_one},
        {2, boundaries_length_two},
        {3, boundaries_length_three},
        {4, boundaries_length_four}};

上面的代码位于单独的命名空间中。
不幸的是，我收到了这个错误：

In file included from /Users/denisivanenko/CLionProjects/UnicodeProcessorCpp/utf8.cpp:5:
/Users/denisivanenko/CLionProjects/UnicodeProcessorCpp/utf8.h:63:58: error: no matching constructor for initialization of 'const std::vector<std::vector<std::array<std::byte, 2> > >'
const std::vector<std::vector<std::array<std::byte, 2>>> boundaries_length_three = {
                                                         ^                         ~
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:528:9: note: candidate template ignored: couldn't infer template argument '_InputIterator'
        vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
        ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:542:9: note: candidate template ignored: couldn't infer template argument '_ForwardIterator'
        vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
        ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:520:9: note: candidate constructor template not viable: requires 2 arguments, but 4 were provided
        vector(_InputIterator __first,
        ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:535:9: note: candidate constructor template not viable: requires 2 arguments, but 4 were provided
        vector(_ForwardIterator __first,
        ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:518:5: note: candidate constructor not viable: requires 3 arguments, but 4 were provided
    vector(size_type __n, const value_type& __x, const allocator_type& __a);
    ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:515:14: note: candidate constructor not viable: requires 2 arguments, but 4 were provided
    explicit vector(size_type __n, const allocator_type& __a);
             ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:517:5: note: candidate constructor not viable: requires 2 arguments, but 4 were provided
    vector(size_type __n, const value_type& __x);
    ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:558:5: note: candidate constructor not viable: requires 2 arguments, but 4 were provided
    vector(const vector& __x, const allocator_type& __a);
    ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:567:5: note: candidate constructor not viable: requires 2 arguments, but 4 were provided
    vector(initializer_list<value_type> __il, const allocator_type& __a);
    ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:578:5: note: candidate constructor not viable: requires 2 arguments, but 4 were provided
    vector(vector&& __x, const allocator_type& __a);
    ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:501:40: note: candidate constructor not viable: requires single argument '__a', but 4 arguments were provided
    _LIBCPP_INLINE_VISIBILITY explicit vector(const allocator_type& __a)
                                       ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:513:14: note: candidate constructor not viable: requires single argument '__n', but 4 arguments were provided
    explicit vector(size_type __n);
             ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:557:5: note: candidate constructor not viable: requires single argument '__x', but 4 arguments were provided
    vector(const vector& __x);
    ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:564:5: note: candidate constructor not viable: requires single argument '__il', but 4 arguments were provided
    vector(initializer_list<value_type> __il);
    ^
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/vector:570:5: note: candidate constructor not viable: requires single argument '__x', but 4 arguments were provided
    vector(vector&& __x)
    ^

错误有点长，但各处的注释消息几乎相同，只是需要和提供的元素数量不同。

谁能帮我初始化这么复杂的结构？ 我使用 C++17、clang 11.0.3 和 CMake 3.17.2。

Answer 1

我设法修复它。 问题出现在我用来代替 std::byte 的nullptr中。