Method assign

system/lib/libcxx/include/__vector/vector.h:1080–1093

template <class _Tp, class _Allocator>
_LIBCPP_CONSTEXPR_SINCE_CXX20 void vector<_Tp, _Allocator>::assign(size_type __n, const_reference __u) {
  if (__n <= capacity()) {
    size_type __s = size();
    std::fill_n(this->__begin_, std::min(__n, __s), __u);
    if (__n > __s)
      __construct_at_end(__n - __s, __u);
    else
      this->__destruct_at_end(this->__begin_ + __n);
  } else {
    __vdeallocate();
    __vallocate(__recommend(static_cast<size_type>(__n)));
    __construct_at_end(__n, __u);
  }
}

template <class _Tp, class _Allocator>
_LIBCPP_CONSTEXPR_SINCE_CXX20 void vector<_Tp, _Allocator>::reserve(size_type __n) {