Re: [Boost-users] question about BOOST_CONCEPT_REQUIRES

Subject: Re: [Boost-users] question about BOOST_CONCEPT_REQUIRES
From: Nathan Ridge (zeratul976_at_[hidden])
Date: 2013-08-18 15:26:54

> #include "boost/concept/requires.hpp"
> #include "boost/concept_check.hpp"
> #include <iterator>
> template <typename T>
> BOOST_CONCEPT_REQUIRES((
> ((boost::ForwardIterator<T>))
> ((boost::LessThanComparable<
> typename std::iterator_traits<T>::value_type
>>))
> ),
> (void)
> )
> bubble_sort(T begin, T end);
>
> if I compile this with gcc 4.5.3 I get some error messages which I don't
> expect to see:

You have an extra pair of parentheses grouping the requirements that
shouldn't be there. It should be just:

BOOST_CONCEPT_REQUIRES(                 // note: removed one '('
    ((boost::ForwardIterator<T>))
    ((boost::LessThanComparable<
        typename std::iterator_traits<T>::value_type
   >))
    ,                                   // note: removed ')'
    (void)
)
bubble_sort(T begin, T end);

See the example usage in the documentation [1].

Regards,
Nate

[1] http://www.boost.org/doc/libs/1_54_0/libs/concept_check/using_concept_check.htm