Re: [boost] [range/iterators/algorithms/phoenix/bind...] Coordinated Approach

From: Joel de Guzman (joel_at_[hidden])
Date: 2008-07-02 18:53:52

Eric Niebler wrote:
> Joel de Guzman wrote:
>> Eric Niebler wrote:
>>> BOOST_TYPEOF can't perfectly distinguish between lvalues and
>>> rvalues.
>>
>> Yeah, that's my basic problem with BOOST_TYPEOF.
>>
>>> I fudge it where I have to,
>>
>> Where do you fudge it? if_then expression? How? How about ordinary 
>> operators like a + b? Do you simply not allow weird uses like:
>>
>> X& operator+(A a, B b)
>>
>> return a reference??
> 
> I use BOOST_TYPEOF to get the type of an expression. Then, I check to 
> see if the expression can bind to a non-const reference using the sizeof 
> trick. If it does, then I treat the result as an lvalue and add a 
> reference to the expression's type. It gets the answer wrong for 
> const-qualified rvalues, but in the above example, it would correctly 
> deduce the type of "A()+B()" to be "X&".

Ah. Makes perfect sense.

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://spirit.sf.net