Re: [boost] [tr1/result of] and l/r values

From: Howard Hinnant (howard.hinnant_at_[hidden])
Date: 2007-01-08 13:03:56

On Jan 8, 2007, at 11:48 AM, Doug Gregor wrote:

>
> On Jan 8, 2007, at 11:32 AM, Tobias Schwinger wrote:
>> Doug Gregor wrote:
>>> TR1 says...
>>>
>>> 	Given an rvalue f of type F and values t1, t2, ..., tN of types T1,
>>> T2, ..., TN, respectively, the type member
>>> 	is the result type of the expression f(t1, t2, ...,tN). The values
>>> ti are lvalues when the corresponding type Ti is
>>> 	a reference type, and rvalues otherwise.
>>
>> Sorry - it seems I missed that last part of the sentence, somehow
>> (maybe
>> by looking at the wrong version?).
>
> It's likely that you were looking at an older draft of TR1. We had
> originally said that everything was an lvalue. We later realized that
> making them rvalues by default, with references signifying lvalues,
> gave us a more functional result_of that was actually easier to deal
> with. The final TR1 draft and the C++0x draft have the revised
> wording I quoted.

We have the same issue with is_convertible (the From parameter).  I  
hope to fix it the same way:

    http://home.twcny.rr.com/hinnant/cpp_extensions/type_traits_changes.html#rel

-Howard