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From: Douglas Gregor (dgregor_at_[hidden])
Date: 2005-01-07 08:19:20

On Jan 7, 2005, at 6:12 AM, Murray Cumming wrote:
> 3. In "Slot Binders"
> Can you expand on this question: "TODO: answer questions: a) What's up
> with the No Clue entry, anyone?", please. In fact, please just ask your
> TODO questions on this mailing list.

So the intent of retype() and retype_return() is to allow casting of
the argument and return types of a function. Are these also required
when performing implicit conversions? For instance, will the following

   long Func3(double val, string str);

   sigc::signal<int, float, string> sig;

If I'm right in assuming that the code will not compile (because the
signatures do not match exactly), then the "No Clue" could be replaced
by "Not Applicable", because
Signals performs all of the implicit conversions.

> 4. Some of the "-ed" comments seem outdated now. It would be nice to
> clean these up.

Replying to some of the -ed comments:

   - Regarding implementing the preferred syntax from Boost.Signals in
libsigc++: it should be trivial, although support for writing function
types is not as portable as we'd like.

   - Regarding bloat factors: they're probably about the same in both
libraries. The only thing we know to do to improve the situation is use
function pointers instead of virtual functions, and to try to be
careful about factoring our templates properly.

   - About ptr_fun/mem_fun: you can use them in either library, if you'd
like to be more explicit.

   - About bind: bind is now in the C++ Library TR (an addendum to the
standard, which should be approved in the near future), so we're forced
to build on it to create any signals & slots library for the standards
committee. (We'll have a long, uphill battle if we try to introduce our
own special binders and don't support bind).

   - Regarding libsigc++'s specialization for T_accumulator=nil: We
don't need to discuss this in a standards proposal, because it's
entirely a quality-of-implementation issue.

   - Regarding Signals and Function: They don't play well together, but
we're going to have to deal with this one way or another because
Function is also part of the C++ Library TR.

And one minor quibble: if we're going to explicitly qualify
Boost.Signals by saying that it was strongly influenced by the work of
Karl Nelson (that's true), I think it's only fair to point out that
libsigc++-2.0's interface was influenced by Boost.Signals.


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