Overloaded lambdas in C++11.

overloaded-lambdas.cpp

#include <iostream>
#include <string>
#include <utility>
using namespace std;

template<class... Fs> struct Overload;

template<class F, class... Fs>
struct Overload<F, Fs...> : Overload<Fs...> {

  Overload(F&& f, Fs&&... fs)
    : Overload<Fs...>(forward<Fs>(fs)...),
      function(move(f)) {}

  template<class... Args>
  auto operator()(Args&&... args) const
    -> decltype(declval<F>()(forward<Args>(args)...)) {
    return function(forward<Args>(args)...);
  }

  using Overload<Fs...>::operator();

private:
  F function;
};

template<> struct Overload<> { void operator()() const {} };

template <class... Fs>
Overload<Fs...> make_overload(Fs&&... fs) { return { forward<Fs>(fs)... }; }

int main() {
  auto overload = make_overload(
    [](const string& s) { return "string: " + s; },
    [](int i) { return "int: " + to_string(i); }
  );
  cout << overload(1) << '\n';
  cout << overload("hi") << '\n';
}