Implement no-op functor using boost::bind

Question

I have a function void get(boost::function<void(void)> callback) { callback(); }. I want to make a call like get(boost::bind(/* don't know what to put here*/)); without implementing any other functions, variables or structs, so that the callback does nothing. Is it possible to implement such "no-op" callback in C++03 ?

Usage of boost::bind() is prefered but not required - may be, there are some other tricks to achieve my goal.

@JoachimPileborg, because that would mean implementing a function, which the OP explicitly wants to avoid. — avakar, Oct 24 '11 at 11:11
@avakar: Joachim is questioning the rationale around not implementing a simple noop function. — David Rodríguez - dribeas, Oct 24 '11 at 11:12
@avakar: "Why not?" is still a good question. If the OP has one bizarre restriction, then he may have others, so it would help to know where the restriction comes from. — Mike Seymour, Oct 24 '11 at 11:12
@avakar, the simplest solution that is still working in older C++ versions is to use a no-op function. If abyss.7 can't do that, and is not able to use C++11 lambdas, then I think there is not much he can do. — Some programmer dude, Oct 24 '11 at 11:28

Mike Seymour · Accepted Answer · 2011-10-24T11:30:16.127

4

You could use something like boost::bind(std::plus<int>(), 0, 0), which should be optimised away to nothing.

It would make the code rather clearer if you relaxed your restriction and defined a no-op functor instead.

edited Oct 24 '11 at 11:30

answered Oct 24 '11 at 11:18

Mike Seymour

249,747
28
448
644

Does a `function` convert implicitly to `function`? – Steve Jessop Oct 24 '11 at 11:30
@SteveJessop: More or less. A `function` can accept a function object that takes no parameters but happens to return a value. – Nicol Bolas Oct 24 '11 at 11:33
@SteveJessop: [Yes](http://ideone.com/V2VPE) (or at least, a functor that returns a value can be converted to a `boost::function` that doesn't). – Mike Seymour Oct 24 '11 at 11:34

Implement no-op functor using boost::bind

1 Answers1