Re: [boost] Re: tuple - pair interoperability

From: Jaakko Jarvi (jajarvi_at_[hidden])
Date: 2004-05-05 13:37:05

On May 5, 2004, at 1:26 PM, David Abrahams wrote:

> Jaakko Jarvi <jajarvi_at_[hidden]> writes:
>
>> On May 4, 2004, at 7:56 PM, Fredrik Blomqvist wrote:
>>
>>> I think it would be convenient if one could treat std::pair as a 
>>> boost
>>> two-tuple.
>>> Both tuples::tie and tuple assignment already work with std::pair
>>> but I've
>>> noticed that the get<> accessor doesn't.
>>>
>>> So, I propose a simple extension to tuples::get<> with the obvious
>>> semantics:
>>> boost::get<0>(p) == p.first
>>> boost::get<1>(p) == p.second
>>>
>>
>> The trouble with get is that pairs live in namespace std, so if pair
>> get's are not
>> in std, they won't get found by ADL. But if we are willing to live
>> with not having ADL,
>> adding gets for pairs would be fine.
>
> Isn't there another problem?  Are references legal arguments for 
> std::pair?
>

No, they aren't and thus we can't make pairs and 2-tuples have 
equivalent behavior in
all cases. However, it seems that adding the get functions for pairs 
would not be
problematic in this sense.

OTOH, what Thorsten suggested, that 2-tuples would inherit from pairs, 
would
not work.

   Jaakko