c++0x: overloading on lambda arity

Question

I\'m trying to create a function which can be called with a lambda that takes either 0, 1 or 2 arguments. Since I need the code to work on both g++ 4.5 and vs2010(which doe

Answer 1

I thought the following would work but it doesn't, I'm posting it for two reasons.

1. To save people the time if they had the same idea
2. If someone knows why this doesn't work, I'm not 100% sure I understand (although I have my suspicions)

Code follows:

#include 
#include 

template 
unsigned arity(std::function) { return 0; }

template 
unsigned arity(std::function) { return 1; }

template 
unsigned arity(std::function) { return 2; }

// rinse and repeat 

int main() 
{
    std::function  f = [](int i) { }; // this binds fine

    //  Error: no matching function for call to 'arity(main()::)'
    std::cout << arity([](int i) { }); 
}