On Thu, May 15, 2008 at 5:59 PM, Marco Costalba <mcostalba@gmail.com> wrote:
On Thu, May 15, 2008 at 8:36 PM, Daniel Walker <daniel.j.walker@gmail.com> wrote:
Yes, so long as the copy constructor of the wrapped function object maintains internal_state.
If the copy c'tor copies the internal state then what's the difference between:
function<float(float,float)> add_floats = plus();
add_floats.target<plus>()->internal_state = 7;
function<int(int,int)> f0 = functional_cast<plus(int,int)>(add_floats);
std::cout << f0.internal_state; // it's 7 !
And
function<float(float,float)> add_floats = plus();
add_floats.target<plus>()->internal_state = 7;
plus tmp( *add_floats.target<plus>() ); // copy c'tor here !
function<int(int,int)> f0 = tmp;
std::cout << f0.target<plus>()->internal_state; // should be 7 the same
I would say It seems that expression
function<int(int,int)> f0 = functional_cast<plus(int,int)>(add_floats);
is very similar to
plus tmp( *add_floats.target<plus>() );
function<int(int,int)> f0 = tmp;
Is this correct ?
Yes, that's basically all there is to it. Really, it's just .... function<int(int,int)> f0 = *add_floats.target<plus>(); ... with error checking. functional_cast is almost as simple as lexical_cast. They're both just syntactic sugar in a way. They communicate the notion that you're converting between two types that represent the same thing. Check out the implementation I sent yesterday. functional_cast's body is just four lines. It's nothing fancy; it's just more expressive and possibly more convenient than directly manipulating pointers to boost::function's innards. Daniel