std::vector<std::string> v = {...};
my_func(v.begin(), v.end());

void my_func(??? i1, ??? i2)
{
  std::for_each(i1, i2, ...); // dumb example implementation
}

template <typename T>
void my_func(T i1, T i2)
{
    std::for_each(i1,i2,...); //dumb example implementation
}

template <typename T, typename U>
void my_func(T i1, U i2)
{
    std::for_each(i1,i2,...); //dumb example implementation
}

auto my_func = [](auto i1, auto i2)
{
    std::for_each(i1,i2,...); //dumb example implementation
};

template<typename Iterator>
void my_func(Iterator startIter, const Iterator endIter)
{
  std::for_each(startIter, endIter, /* lambda */);
}

const auto defaultCallable = [](auto element){ }; // does nothing
template<typename Iterator, typename Callable = decltype(defaultCallable)>
void my_func(Iterator startIter, const Iterator endIter, Callable func = {})
{
    std::for_each(startIter, endIter, func);
}

template <template<typename...> class Iterable, typename T>
void foo(
    const Iterable<T>& y // the container
){
    for (auto&& e : y){
        // e is the 'thingy' in the container.
    }
}