Re: [Boost-users] [Lambda] Handling Bind/Lambda name clashes.

Subject: Re: [Boost-users] [Lambda] Handling Bind/Lambda name clashes.
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-04-07 10:01:51

AMDG

On 04/06/2011 09:03 PM, Eric Niebler wrote:
> On 4/7/2011 1:02 AM, Steven Watanabe wrote:
>> On 04/06/2011 10:46 AM, Peter Dimov wrote:
>>> Eric Niebler wrote:
>>>
>>>> I'm saying that boost::function should actually be defined in
>>>> boost::function_adl_block and be imported into the boost namespace
>>>> with a using declaration.
>>>
>>> This makes no sense to me. boost::bind is the unconstrained function
>>> template found by ADL, not boost::function. You ought to be arguing that
>>> boost::bind should be in an ADL-blocking namespace. Of course this will
>>> break all code that relies on ADL to omit the boost:: qualification.
>>>
>>
>> The problem is that it's much easier to put
>> a class in an ADL blocking namespace, than to
>> put a class in al ADL blocking namespace:
>
> Huh?
>

Oops.  That should be "it's much easier to put
a class in an ADL blocking namespace, than to
put a /function/ in an ADL blocking namespace"

>> namespace bind_adl_block
>> {
>>      template<class F>
>>      void bind(F f);
>> }
>> using bind_adl_block::bind; // bind can still be found by ADL
>>
>> The only way to do it is with a using
>> directive:
>>
>> using namespace bin_adl_block;
>>
>> but this is fragile for other reasons.
>
> Wow, it seems there's a lot I don't know. Isn't this allowed:
>
>    using bind_adl_block::bind;
>

It's allowed, but it doesn't work,
because a function imported via
a using declaration /can/ be found
by ADL.

> And what is wrong with leaving bind in the boost namespace as I was
> suggesting and define boost::function like this:
>
>    namespace boost {
>      namespace function_adl_block {
>        template<class Sig>
>        struct function {...};
>      }
>      using function_adl_block::function;
>    }
>
> Now the "boost" namespace is no longer associated with boost::function,
> and boost::bind won't be found by ADL. Unless I'm mistaken, and a quick
> test with comeauonline suggests I'm not. But Steven and Peter are
> usually right about this stuff, so I'll patiently wait to be corrected
> and learn. :-)
>

Yes, you're correct about this.

In Christ,
Steven Watanabe