[boost] Re: reference binding

From: Dill, John (john-dill_at_[hidden])
Date: 2004-04-15 11:08:17

> > While having pass-by-value
> > may be more convenient and occur more often, the counter-intuitiveness
> > of the semantics will lead to subtle bugs in people's code who
> > misunderstand or forget bind's behavior in this area.
> 
> A bold prediction in the face of contradictory evidence.

Can you elaborate?  You may have no problems understanding the library, but the first time I tried to bind with a reference, I ran into the same confusion.  I am speaking from my own limited experience with the library.  I've read the documentation:

// Start of docs
The arguments that bind takes are copied and held internally by the returned function object. For example, in the following code: 

int i = 5;

bind(f, i, _1);

a copy of the value of i is stored into the function object. boost::ref and boost::cref can be used to make the function object store a reference to an object, rather than a copy: 

int i = 5;

bind(f, ref(i), _1);
// End of docs

I know this makes it explicit that you need a ref or cref to have bind store a reference to an object, but there is no reasoning behind this design decision in the documentation, or that I can find in the implementation and I've not stumbled across it in the mail archives.

Best,
John