如何在 c++98 中使用我的自定义 enable_if？

Question

I am currently making custom Vector container for the purpose of studying. My assignment has limitation that i should use c++98 version.

But during the implementation of "insert" function, i have problem which i explained in this link .

I got some hints that i should use "enable_if" from link. But because I have no right to use c++11 (enable_if defined) extention so i made enable if and is_integral by myself.

This is previous one.

// 1
template <typename T, typename Alloc>
void vector<T, Alloc>::insert(iterator position, size_type n, const value_type &val)

// 2
template <typename T, typename Alloc>
template <class InputIterator>
void vector<T, Alloc>::insert(iterator position, InputIterator first, InputIterator last)

This is the code that i changed with custom enable_if and is_integral

// 1
template <typename T, typename Alloc>
void vector<T, Alloc>::insert(iterator position, size_type n, const value_type &val)

// 2
template <typename T, typename Alloc>
template <class InputIterator, class  = typename ft::enable_if<!ft::is_integral<InputIterator>::value>::type>
void vector<T, Alloc>::insert(iterator position, InputIterator first, InputIterator last)

It works well if i don't give "-std=c++98" option to compiler, but if i give it, it said

./Vector.hpp:87:33: warning: default template arguments for a function template are a C++11 extension [-Wc++11-extensions]
  ...class  = typename ft::enable_if<!ft::is_integral<InputIterator>::value>::type>
     ^

Could you please help me to adapt my code for c++98 extension?

Answer 1

std::enable_if and std::is_integral were introduced in C++11. You can reimplement them like that if you compile with the --std=c++98 flag.

You can find all the specifications to do that here and here .