Take a reference if lvalue and make a copy if rvalue i.e. make rvalue persistent.

I'm pretty new in move and lvalue semantics. And I have the impression I'm doing it wrong. Here the code I want to be able to write once FunctContainer is implemented:

std::function<double(double)> f = [](double x){return (x * x - 1); };

FunctContainer fc1 = FunctContainer(f);

FunctContainer fc2 = FunctContainer([](double x){return (x * x - 1); });

I want to write FunctContainer's ctors so that the lifetime of the function stored in fc1 is the one of f and the lifetime in fc2 of the contained function is the lifetime of fc2 itself.

I have written something (see below) but I'm not really satisfied (I got it wrong).

This is correct c++ but wrong behavior: f_ expires after the call to the constructor when f_ is an rvalue.

class FunctContainerWRONG{
public:
  IntegrandNotProjecting(const std::function<double(double)>& function)
    : f_(function){}
  IntegrandNotProjecting(const std::function<double(double)>&& function)
    : f_(std::move(function)){}
  const std::function<double(double)>& f_;
private:
};

This looks awful at me and probably is not correct c++ but is intended to explain in pseudocode what the desired behavior looks like. If possible I want to avoid to constuct a brand new object and I just want to let my object "persist":

class FunctContainer{
public:
  FunctContainer(const std::function<double(double)>& function)
    : f_p(nullptr), 
      f_(function){}
  FunctContainer(const std::function<double(double)>&& function)
    : f_p()std::make_shared<std::function<double(double)>>(function)), 
      f_(*f_p){}
private:
    std::shared_ptr<std::function<double(double)>> f_p;
    const std::function<double(double)>& f_;
};