Re: Boost.function enhanced (a little)
* Paul Bibbings:
jaybus56 wrote:
I could never understand, why the boost.function class/es do/es/n't
support what Loki's functor can do: hassle-free taking an instance plus
member function...
I personally feel that it is an advantage of the Boost implementation that
it
strives to keep the semantics of 'function wrapping' and 'binding'
separate by
encapsulating them in distinct libraries. If we look at the example uses
in the
Loki documentation:
Loki::Function<int (int, int)> f(&FreeFunction);
Loki::Function<int ()> f(&object, &ObjectType::MemberFunction);
we find the two mixed, the second involving binding to an object of the
type,
the first involving no binding.
This is mainly a shortcoming of the C++ language, that it doesn't support
delegates (member routine bound to object). You're confusing general
argument
binding with support for delegates. That is, it's only incidental that
supporting a logically complete set of "callable entities" involves some
internal argument binding, and users of the library don't have to consider
that.
It's positive, not negative, that the Loki library tries to make up for that
language deficiency, that it addresses the points of /practical usage/ and
/completeness/ (for the concept of "callable entity").
Loki presents an interface that with a more complete language would not have
required binding, and thus it frees client code from having to do the
binding
(implementation level stuff) in the cases of delegates.
The argument that the library implementation may become more complex, that
hey,
if we're to present a practical interface then we have to do some
implementation
level stuff in the implementation instead of forcing that on the client
code, I
fail to understand that mode of thinking: the purpose of a library is (or
should
ideally be!) to make client code simpler by taking on some burdens, not to
be as
pretty as possible when viewed through certain colored glasses.
It's a deficiency of Boost that it requires the client code to mix function
wrapping and binding for the case of delegates, that it passes that burden
on to
the client code instead of dealing with it.
Cheers & hth.,
- Alf
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