From: Hervé Brönnimann (hervebronnimann_at_[hidden])
Date: 2006-12-09 09:32:22
Indeed, I tried and to my surprise it doesn't work (both boost::bind
(&draw, _1, _2)(1,2,3,4) and boost::bind<void>(&draw, _1, _2)(1,2,3,4)).
But there is no reason (other than design) it couldn't. In fact, our
company's version of bind (I mean at Bloomberg LP) *does* allow extra
arguments to be passed to a non-explicit binder (i.e. one whose
signature cannot be determined from the bound object at binding
time). The extra unused arguments are simply dropped.
Now I could imagine that the authors of boost.bind do *not* want to
allow this for type safety reasons, i.e. matching the signature
exactly. That would be understandable. In that case I'd say you
have a point.
-- Hervé Brönnimann hervebronnimann_at_[hidden] On Dec 8, 2006, at 5:37 AM, ali f wrote: > Boost.Bind can indeed be used to decrease the number of args a > function can > take, but it can't be used to increase the number of args a > function can > take. In the example I gave in my original post, the callback: > > bool callback(int,int,bool,int); > > and you have a functon > > bool draw(int,int) > > You can't use bind to assign "draw" to "callback". args_cast can be > used > though. > > - ali > > ----- Original Message ----- > From: "me22" <me22.ca_at_[hidden]> > Newsgroups: gmane.comp.lib.boost.devel > Sent: Friday, December 08, 2006 6:30 PM > Subject: Re: new utility: function parameter caster > > >> On 12/7/06, ali f <k9eks_at_[hidden]> wrote: >>> a) wrap the function in a struct and overload operator () >>> b) change the signature (but then change all places where you've >>> invoked >>> the >>> function already) >>> >> c) Use Boost.Bind. >> >>> From http://boost.org/libs/bind/bind.html#with_functions : >> bind(f, _2, _1)(x, y); // f(y, x) >> bind(g, _1, 9, _1)(x); // g(x, 9, x) >> bind(g, _3, _3, _3)(x, y, z); // g(z, z, z) >> bind(g, _1, _1, _1)(x, y, z); // g(x, x, x) >> Note that, in the last example, the function object produced by >> bind(g, _1, _1, _1) does not contain references to any arguments >> beyond the first, but it can still be used with more than one >> argument. Any extra arguments are silently ignored, just like the >> first and the second argument are ignored in the third example. >> _______________________________________________ >> Unsubscribe & other changes: >> http://lists.boost.org/mailman/listinfo.cgi/boost >> > > _______________________________________________ > Unsubscribe & other changes: http://lists.boost.org/mailman/ > listinfo.cgi/boost
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk