In a nutshell, auto cannot be used in an effort to omit the actual types of function arguments, so stick with function templates and/or overloads. auto is legally used to automatically deduce the types of variables:
auto i=5;
Be very careful to understand the difference between the following, however:
auto x=...
auto &x=...
const auto &x=...
auto *px=...; // vs auto px=... (They are equivalent assuming what is being
// assigned can be deduced to an actual pointer.)
// etc...
It is also used for suffix return types:
template <typename T, typename U>
auto sum(const T &t, const U &u) -> decltype(t+u)
{
return t+u;
}