Re: [boost] [Review] Boost.Type Traits Extension by Frederic Bron

Subject: Re: [boost] [Review] Boost.Type Traits Extension by Frederic Bron
From: Vicente Botet (vicente.botet_at_[hidden])
Date: 2011-03-15 05:34:44

Frédéric Bron wrote:
> 
> 
>> There is a declval function on Boost.Utility that creates a rvalue
>> reference
>> that could be used instead of the make() function. Please could you check
>> if
>> this function is adapted to your needs?
> 
> Unfortunately I need a l-value, espacially for += type of operators.
> 

Oh, I see.

>> The limitation related to the implicit conversion could maybe reduced if
>> the
>> traits take care of a special trait giving the list of classes that a
>> class
>> is implicitly convertible to
>>
>> Â implicitly_convertible_seq::type
>>
>> With this trait the has_operator_name traits could try to check before in
>> this type sequence to avoid the ambiguity. The main problem is that this
>> trait needs to be specialized for each class only once in a centralized
>> way,
>> which is quite restrictive. Of course this can be defined on top of the
>> existing traits, so it is not a blocking issue for me, but I would like
>> to
>> know what other think of the approach.
> 
> I cannot comment on that as I do not see exactly how this would be
> implemented. Sorry.
> 

I will develop it later.

> 
>> Last I agree that the use of equal should be replaced by assign when
>> assignment is intended
>> += has_operator_plus_equal -> has_operator_plus_assign
>> -= has_operator_minus_equal -> has_operator_minus_assign
> 
> Why? is it to avoid confusion with "equal to"?
> I like plus_equal because plus is a sign and equal is also a sign. So
> I think it is easier to remember.
> 

No, it is because the intended behavior on the builtin types is to make an
assignment. Remember in C++ user defined types should follow the builtin
semantics when possible. 

Best,
Vicente

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