Initializing unspecified number of integers in a class

[Morapoly]

How can I define a class that receives unspecified number of integers?
My purpose is code a program that acts similar "vector".

[mbozzi]

With std::initializer_list.
You can also consider a variadic template constructor, but this is less ideal because of the overload resolution mechanism's preference for that constructor over many other near matches.

# include <memory>
# include <initializer_list>
# include <iostream>

class A { 
  std::ptrdiff_t size;
  std::unique_ptr<int[]> data; 
  
  template <typename Iterator>
  A(Iterator&& b, Iterator&& e)
    : size{std::distance(b, e)}
    , data{std::make_unique<int[]>(size)} 
  { std::copy(b, e, data.get()); }

public:
  A(std::initializer_list<int> l)
    : A(l.begin(), l.end()) {}
  
  int* begin() const { return data.get(); }
  int* end()   const { return data.get() + size; }
};

int main() { 
    A a { 1, 2, 3, 4, 5 }; 
    for (auto elt: a) std::cout << elt << '\n';
}

[Morapoly]

thanks;but
In debugging this program below error appears:

'std::copy::_Unchecked_iterators::_Deprecate': Call to 'std::copy' with parameters that may be unsafe - this call relies on the caller to check that the passed values are correct. To disable this warning, use -D_SCL_SECURE_NO_WARNINGS. See documentation on how to use Visual C++ 'Checked Iterators' Project2 c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.11.25503\include\xutility

can you resolve it?
I work with visual studio 2017.

[mbozzi]

this call relies on the caller to check that the passed values are correct

Who would have guessed.

In all seriousness, Microsoft seems to be over-eager.

Live demo:
http://coliru.stacked-crooked.com/a/e9c29239f9dda0bf

I would most likely disable that message, for what it's worth. But if you would prefer not to, you may use this non-standard iterator adaptor as per the instructions here:
https://stackoverflow.com/questions/12062262/stditerator-pointers-and-vc-warning-c4996/12063174#12063174

See also:
https://msdn.microsoft.com/en-us/library/aa985965.aspx

Alternatively, you may change the design. No matter what the compiler says about std::copy, std::initializer_list is still the subject of the answer - the rest of the code is only an example.