Boost logo

Boost :

From: Douglas Gregor (gregod_at_[hidden])
Date: 2002-05-11 13:54:53

On Saturday 11 May 2002 12:22 pm, you wrote:
> Wouldn't make_function work for std::unary_function, std::binary_function
> and
> boost::function too? But yes, handling arbitrary function objects would be
> difficult.

Yes, it could be made to work with unary_function, binary_function, and

> Well I guess I'll write make_function myself then. It won't work for any
> function
> object but I can live with that.

That's probably the best option. Sorry :(

> Just one thing though, I'd like it to work for the result of a boost::bind
> as well.
> But the result of a boost::bind is implementation-defined according to the
> documentation. So there is no way to portably create boost::bind overloads
> for
> make_function, right?

It wouldn't work anyway, because boost::bind function objects don't have
exact argument types to deduce. For instance, how would the following work?

template<typename T>
struct add_to {
  typedef T result_type;
  template<typename U>
  T& operator()(T& t, const U& u) const
    return t += u;

std::string& foo;
make_function(bind<std::string&>(add_to<std::string>(), ref(foo), _1));

The boost::bind function object takes at least 1 argument (any more would be
ignored), but the type of that first argument isn't specified. Boost.Function
doesn't (and can't) do partial bindings.

> > If we _did_ have a working set of function traits, it would be possible
> > to make Boost.Function objects implicitly constructed only from function
> objects
> > that are callable by the Boost.Function object.
> This seems to me as an awesome addition to Boost.Function! Too bad there
> are compilers out there that don't support the needed functionality. :(
> Dirk Gerrits

There are workarounds for most compiler deficiencies, but of course we won't
know until someone tries. I'll work on it sometime.


Boost list run by bdawes at, gregod at, cpdaniel at, john at