Demonstration of Mathias Gaunard's overloaded function object technique. See also https://gist.github.com/3779508

lambda-overload.cpp

// Copyright Dave Abrahams 2012. Distributed under the Boost
// Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

template<class...Fs> struct overloaded;

template<class F1, class...Fs>
struct overloaded<F1, Fs...> : F1, overloaded<Fs...>::type
{
    typedef overloaded type;

    overloaded(F1 head, Fs...tail)
        : F1(head),
          overloaded<Fs...>::type(tail...)
    {}
    
    using F1::operator();
    using overloaded<Fs...>::type::operator();
};

template<class F>
struct overloaded<F> : F
{
    typedef F type;
    using F::operator();
};

template<class...Fs>
typename overloaded<Fs...>::type overload(Fs...x)
{ return overloaded<Fs...>(x...); }

auto f = overload(
    [](int x) { return x+1; },
    [](char const* y) { return y + 1; },
    [](int* y) { return y; });

int main()
{
    int a = f(1);
    char const* p = f("hello");
    int* r = f(&a);
}

In generic code for unary case overload type of returning value does not match the returning type of the function.