Re: [ALACPP] boost::function shortcoming

[Greg Underwood <gunderwoodhsd@xxxxxxxxxxxxx>]

On Tuesday 29 July 2003 04:52 pm, Christopher Smith wrote:
> We talked about this at our last meeting didn't we? Oh wait, you weren't
> there..... ;-)
>
> On Tue, 2003-07-29 at 16:39, Gavin Doughtie wrote:
> > So, I was wondering if there was a way to compare two boost::function
> > objects to see if they were bound to the same function. Greg, quite
> > sensibly, wanted a unit test to ensure that the default bindings were
> > correct, and there was no way that we could find to dig the original
> > function pointer out and check it.
>
> Of course another approach is to make a dummy function that just toggles
> a flag if it is called, and then test if boost::function invokes that
> function.

But that's not what I want to test.  That just tells me that the over-all 
system works, that I can assign an arbitrary function to the 
boost::function<...> magic.  What I want to test is if a particular function 
was in fact assigned to a particular boost::function<...> foo;.  IE: foo == 
funcptr;.  Without the ability to do that, I have to form the oppinion that 
this feature of boost is rather under-implemented.

> > Fortunately, in this case we were able to use a raw function pointer, but
> > it begs the question -- I could see not comparing two boost::bound
> > function objects as the member instances might be different, but even
> > then I'd like to do some kind of type checking.
>
> Given that operator== is deliberately left undefined, and the way they
> are doing their abstraction, I can't see a way to do what you want.

Gavin and I spent some time looking at the docs but didn't come to an 
understanding of why they deliberatly left == undefined... anyone care to 
clarify?  They said something about some sort of loophole caused by the 
safe_bool()?

-Greg
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