Hi there, I'd like to make sure that some of my classes are only used with particular value types. This is easy enough to implement for integers, using BOOST_CONCEPT_ASSERT((boost::Integer<T>)) . However, there is no boost::FloatingPoint<T>, which is a bit odd. The following, easy code seems to do what I want, but reqires inclusion of boost/concept/detail/concept_def.hpp /*****************************************************************/ namespace boost { BOOST_concept(FloatingPoint, (T)) { BOOST_CONCEPT_USAGE(FloatingPoint) { x.error_type_must_be_a_floating_point_type(); } private: T x; }; template <> struct FloatingPoint<long double> {}; template <> struct FloatingPoint<double> {}; template <> struct FloatingPoint<float> {}; } /*****************************************************************/
From what I understand, this means that I am relying on implementation details with the above code.
Is there any way to do the above in a portable way ? Thanks and Best Regards, Ruediger P.S.: If the above seems acceptable, please feel free to include it in Boost.Concept.
On Wed, Sep 15, 2010 at 2:02 PM, Ruediger Berlich <ruediger.berlich@iwr.fzk.de> wrote:
Hi there,
I'd like to make sure that some of my classes are only used with particular value types. This is easy enough to implement for integers, using BOOST_CONCEPT_ASSERT((boost::Integer<T>)) . However, there is no boost::FloatingPoint<T>, which is a bit odd.
The following, easy code seems to do what I want, but reqires inclusion of boost/concept/detail/concept_def.hpp
/*****************************************************************/
namespace boost { BOOST_concept(FloatingPoint, (T))
From what I understand, this means that I am relying on implementation details with the above code.
Yes. Why did you use the undocumente BOOST_concept macro? That only exists for backward compatibility with older uses of the BCCL.
Is there any way to do the above in a portable way?
// untested #include <boost/type_traits/is_floating.hpp> #include <boost/mpl/assert.hpp> template <class T> struct FloatingPoint { BOOST_MPL_ASSERT((boost::is_floating<T>)); };
P.S.: If the above seems acceptable, please feel free to include it in Boost.Concept.
If what I suggested works out for you, would you mind submitting a patch to Trac? -- Dave Abrahams BoostPro Computing http://www.boostpro.com
Dear Dave, thanks a lot! Dave Abrahams wrote:
On Wed, Sep 15, 2010 at 2:02 PM, Ruediger Berlich [...]
From what I understand, this means that I am relying on implementation details with the above code.
Yes. Why did you use the undocumente BOOST_concept macro? That only exists for backward compatibility with older uses of the BCCL.
This is an almost verbatim copy of the code used for Integer<T>, SignedInteger<T> etc. in $BOOSTROOOT/include/boost/concept_check.hpp .
Is there any way to do the above in a portable way?
// untested #include <boost/type_traits/is_floating.hpp> #include <boost/mpl/assert.hpp>
template <class T> struct FloatingPoint { BOOST_MPL_ASSERT((boost::is_floating<T>)); };
P.S.: If the above seems acceptable, please feel free to include it in Boost.Concept.
If what I suggested works out for you, would you mind submitting a patch to Trac?
The following example, using your suggestion, works for me (g++ 4.4.3 / Ubuntu 10.04). See further below for comments regarding a patch and trac item: //------------------------------------------------------------------------ #include <iostream> #include <boost/cstdint.hpp> #include <boost/concept_check.hpp> #include <boost/type_traits/is_floating_point.hpp> #include <boost/mpl/assert.hpp> /*****************************************************************/ namespace boost { template <class T> struct FloatingPoint { BOOST_MPL_ASSERT((boost::is_floating_point<T>)); }; } /*****************************************************************/ template <class T> class integerWrapper { BOOST_CONCEPT_ASSERT((boost::Integer<T>)); public: integerWrapper() { /* nothing */ } }; template <class T> class fpWrapper { BOOST_CONCEPT_ASSERT((boost::FloatingPoint<T>)); public: fpWrapper() { /* nothing */ } }; main() { integerWrapper<boost::int32_t> iW; fpWrapper<double> fW_double; fpWrapper<float> fW_float; // fpWrapper<char> fW_char; // fails to compile, just as it should // fpWrapper<boost::int32_t> fW_int32; // fails to compile, just as it should } //------------------------------------------------------------------------ It does appear, though, as if the better solution for me would be to directly use BOOST_MPL_ASSERT in my code, of which I wasn't aware prior to your answer. I've been looking all along for a something that lets me use type traits to check the types of an entire template class (instead of just single functions, as I've done previously with enable_if). As to the patch: I'm happy to do this for concept_check.hpp . Kind Regards / Mit freundlichen Gruessen, Ruediger Berlich
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Dave Abrahams -
Ruediger Berlich