Default argument for a functor in a templated parameter

From C++11 you can already do that:

template <typename Functor = int(int)>
int run_new(int x, Functor func = [](int a){ return a+1; }) 
{
    return func(x);
}

Just add an overload for this.

template <typename Functor>
int run_new(int x, Functor func) 
{
    return func(x);
}

int run_new(int x) 
{
    return run_new(x, [](int a){ return a+1; });
}

Allows you to get around not beening able to have a lambda expression as a default function argument.