Re: [Boost-users] upcoming Switch library review Jan 5th - Jan 9th

From: Steven Watanabe (steven_at_[hidden])
Date: 2008-01-05 13:35:12

AMDG

Tobias Schwinger <tschwinger <at> isonews2.com> writes:

> dan marsden wrote:
> > Why is the fall through behaviour to throw an exception?
> 
> I too tripped over this one, yesterday.
> 
> <snip>

The other option is an assertion.  Is that any better?
Or should a void return type be a special case?

> > 
> > I'm not too clear with the documentation what the parameter 'n' can be? 
> 
> "MPL sequence of integer constants" and "equal to" are sorta fuzzy in 
> this context, too.
> 
> <snip>

OK.  I'll tighten this up.

> > The parameter section does not specify the arities of the 2 function 
> > object parameters, I had to deduce them from the example.

I'll be more precise.

> > Why do these 
> > have to be function objects, and not just any callable type, including 
> > ordinary functions
> > <snip>

You can use a plain function for default_.

> I think "function object" is still the correct term even if you /can/ 
> use a function pointer for the default: A pointer is an object and a 
> function pointer is a function object. A pointer to member function is 
> also Callable -- and we probably wouldn't want to support this case...

Even if it's specified as Callable, it's ok
because void int::*() e.g. is illegal anyway.

> Of course there are no pointers to templates, so using a function 
> pointer for anything but the default is pretty pointless. So is trying 
> to handle varying result types -- maybe the result type should be passed 
> in with another template parameter?

I'd rather leave it as result_of<F()>::type.

> > Also, why is 'default_' unary, the default in a standard switch 
> > statement does not access the switch parameter, and the example does
> > not exploit this feature either. Why not just a nullary function?
> 
> I really like this feature a lot:
> 
> If you can't react to some case at compile time doesn't mean you can't 
> at runtime...

Exactly.

> > And finally, as the introduction mentions the efficiency of the 
> > standard switch statement, could the docs show some performance
> > stats for the library code for comparison?
> > 
> 
> Yes, please!

Will do.

In Christ,
Steven Watanabe