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

Subject: Re: [boost] [Review] Boost.Type Traits Extension by Frederic Bron
From: Joachim Faulhaber (afojgo_at_[hidden])
Date: 2011-03-17 16:56:29

2011/3/17 Jeffrey Lee Hellrung, Jr. <jhellrung_at_[hidden]>:
> On 3/17/2011 7:17 AM, Joachim Faulhaber wrote:
>>
>> 2011/3/17 Joachim Faulhaber<afojgo_at_[hidden]>:
>
> [...]
>>>
>>> thank you again for implementing this has_operator extension. I've
>>> found some problems. In the ICL I have an operator +
>
> [...]
>>
>> template<class Type>
>> inline typename enable_if
>> <is_associative_element_container<Type>, Type>::type
>> operator + (Type object, const Type&  operand);
>>
>>>
>>> and is seems that more overloads are checked valid as actually exist.
>>> Is this intentional?
>>>
>>> BOOST_AUTO_TEST_CASE(has_op_extension_qualifiers)
>>> {
>>> typedef int T;
>>> typedef interval_set<T>               IntervalSetT;
>>> typedef IntervalSetT::interval_type IntervalT;
>>>
>>> // This is supposed to succeed
>>> BOOST_CHECK((has_operator_plus<IntervalSetT, const IntervalSetT&,
>>> IntervalSetT>::value));
>>>
>>> BOOST_CHECK((!is_convertible<const IntervalSetT&,
>>> IntervalSetT&>::value));
>>>
>>> // These are supposed to fail, but they succeed
>>> BOOST_CHECK((has_operator_plus<IntervalSetT, IntervalSetT&,
>>> IntervalSetT>::value));
>>> BOOST_CHECK((has_operator_plus<IntervalSetT, IntervalSetT,
>>> IntervalSetT>::value));
>>> BOOST_CHECK((has_operator_plus<IntervalSetT, IntervalSetT,
>>> IntervalSetT const&>::value));
>>> }
>
> An operator trait allows implicit conversions in the arguments.  In fact,
> the current implementation strategy *must* allow implicit conversions in the
> arguments, i.e., I wouldn't know how to detect *exact* signatures.

Does this mean that, since

is_convertible<T, T&> and
is_convertible<T, T const&>

has_operator_xxx comes with a built in type qualifier abstraction,
which means that it does never make sense to use type qualifiers with
has_operator_xxx<...>::value meta expressions?

Joachim

-- 
Interval Container Library [Boost.Icl]
http://www.joachim-faulhaber.de