Re: [boost] about function.hpp

From: Doug Gregor (gregod_at_[hidden])
Date: 2001-05-01 17:14:51

On Tuesday 01 May 2001 12:02, you wrote:
> On Monday 30 April 2001 05:34, you wrote:
> > i have a question about the just uploaded function
> > Callback/function-04-29.zip by Doug Gregor (great stuff btw):
> >     is it possible to make the operator () methods const? or is/was there
> > a good reason for making them non-const?
> > (saves me lots of mutable's  if they're const;-)
>
> I see two options for making it const, each with its semantic problems:
> 	1) Just make function::operator() const, but constness won't be passed
> through to underlying function objects, so we're dealing with a semantic
> grey area.
> 	2) Have both a const and a non-const version, and pass an "is_const" flag
> so that function objects will be invoked as const or non-const and the
> constness will be passed through. However, this requires a const version of
> operator() to be defined for any function object regardless of whether it
> is used or not.
[snip]

I went with option #2 because it is much less surprising for the user. The 
updated archive is at:

http://groups.yahoo.com/group/boost/files/Callback/function-05-01.zip
or
http://groups.yahoo.com/group/boost/files/Callback/function-05-01.tgz

Now includes
        - const & non-const operator()
        - make_function to build a function object from a function pointer.

        Doug Gregor