Re: [Boost-Users] boost::function2's copy constructor expensive - why?

From: Douglas Gregor (gregod_at_[hidden])
Date: 2003-02-10 12:01:16

On Monday 10 February 2003 07:19 am, Markus Werle wrote:
> Before I dig in that code: where do those copies come from?
> Is that the normal behaviour triggered ny operator() or is that a
> hint that I use them the wrong way?

operator() will not make any copies. The overhead of operator() comes from 
calls through function pointers.

The most likely reason I can think of for the multitude of copy constructions 
after the array is built is that you are passing boost::function2 objects to 
routines that take function objects by value. Unfortunately, this is the 
common way to pass function objects, e.g.,

  template<typename F>  void do_something(F f) { ... }

If you are using the C++ standard library algorithms, that may be your 
culprit. You can pass a "reference" to those algorithms by changing 'f' 
parameters to:
  boost::bind(ref(f), _1, _2)

        Doug