Question

这段c ++代码无法编译。有人知道为什么吗？

#include <functional>
#include <algorithm>
#include <vector>
#include <iostream>

int main(int a, char** v) {

        std::vector<uint32_t> v1 {1,2,3,4};
        std::vector<uint32_t> v2 {0};
        std::vector<uint32_t> v3 {5,4,3,11};
        std::vector<uint32_t> v4 {10,11,2};


        auto vector_is_subset = [] (const std::vector<uint32_t> a, const std::vector<uint32_t> b) -> bool {

                std::sort(a.begin(), a.end());
                std::sort(b.begin(), b.end());
                return std::includes(a.begin(), a.end(), b.begin(), b.end());
        };


        std::vector<uint32_t> f {};

        if (v1.empty() || v2.empty() || v3.empty() || v4.empty() ){
                std::cout << "a vector is empty" << std::endl;
        }


        return 0;
}

我得到以下输出

g ++ a.cpp -std = c ++ 14

在/ usr / include / c ++ / 7 / algorithm：62：0包含的文件中，来自a.cpp：2：

/ usr / include / c ++ / 7 / bits / stl_algo.h：实例化为“ void std :: __ insertion_sort（_RandomAccessIterator，_RandomAccessIterator， _Compare）[with _RandomAccessIterator = __gnu_cxx :: __ normal_iterator>; _Compare = __gnu_cxx :: __ ops :: __ Iter_less_iter]’： /usr/include/c++/7/bits/stl_algo.h:1885:25：从'void必需 std :: __ final_insertion_sort（_RandomAccessIterator， _RandomAccessIterator，_Compare）[with _RandomAccessIterator = __gnu_cxx :: __ normal_iterator>; _Compare = __gnu_cxx :: __ ops :: __ Iter_less_iter]’ /usr/include/c++/7/bits/stl_algo.h:1971:31：从'void必需 std :: __ sort（_RandomAccessIterator，_RandomAccessIterator，_Compare） [使用_RandomAccessIterator = __gnu_cxx :: __ normal_iterator>; _比较= __gnu_cxx :: __ ops :: _ Iter_less_iter]” /usr/include/c++/7/bits/stl_algo.h:4836:18：“void”中必填 std :: sort（_RAIter，_RAIter）[with _RAIter = __gnu_cxx :: __ normal_iterator>]’a.cpp：16：31：从此处开始 /usr/include/c++/7/bits/stl_algo.h:1852:17：错误：分配只读位置“ __first .__ gnu_cxx :: __ normal_iterator> :: operator *（）” * __ first = _GLIBCXX_MOVE（__ val）;

Answer 1

std::sort修改了容器以使其排序，但是您将lambda的参数声明为const：

auto vector_is_subset = [] (const std::vector<uint32_t> a, const std::vector<uint32_t> b) -> bool
                         // ^^^^                           ^^^^^

删除它们，它应该可以正常编译。

C ++代码无法编译并产生奇怪的错误

1 个答案: