const向量的C向量数组元素 [英] const vector of Pointers to C-Style Array Elements
问题描述
说我有一个C风格的数组: int foo [] {1,2,3,4,5};
Say I have a C-style array like this: int foo[]{1, 2, 3, 4, 5};
现在我想构造一个 const std :: vector< int *> pFoo {& foo [0],& foo [1],& foo [2],& foo [3],& foo [4]};
我可以使用 initializer_list
,只要我知道所有的元素。但是说,我只是通过 foo
和它的大小。在设计时可以初始化 pFoo
而不知道 foo
的大小?
I can use the initializer_list
as long as I know all the elements. But say that I was just passed foo
and it's size. Can I initialize pFoo
without knowing the size of foo
at design time?
推荐答案
您可以创建一个代理函数来初始化你的向量。这使用模板扣除自动查找数组的大小。
You can create a "proxy" function that initializes your vector. This uses template deduction to find the size of the array automatically.
template <typename T, std::size_t N>
std::vector<int*> init_vector(T (&foo)[N])
{
std::vector<int*> vec;
for (std::size_t i = 0; i < N; ++i)
{
vec.push_back(&foo[i]);
}
return vec;
}
int main()
{
int foo[] {1, 2, 3, 4, 5};
const std::vector<int*> vec = init_vector(foo);
for (auto v : vec) std::cout << *v << " ";
}
或者,如果您可以使用Boost,您可以使用 boost :: make_transform_iterator :
Alternatively, if you're able to use Boost, you can use boost::make_transform_iterator:
int* convert_to_ptr(int& i)
{
return &i;
}
int main()
{
int foo[] {1, 2, 3, 4, 5};
const std::vector<int*> vec {
boost::make_transform_iterator(std::begin(foo), convert_to_ptr),
boost::make_transform_iterator(std::end(foo), convert_to_ptr)
};
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