"0 + 0" and "0 - 0" lead to a compile time error

[iorate <iorate_stage@…>]

The following code causes a compilication error under GCC 4.5, 4.6 and VC 10.

#define BOOST_RATIO_EXTENSIONS
#include <boost/ratio.hpp>

using namespace boost;

typedef ratio_add<ratio<0>, ratio<0> >::type zero_plus_zero;
typedef ratio_subtract<ratio<0>, ratio<0> >::type zero_minus_zero;

Error messages (GCC 4.6.0):

In file included from C:/Opt/boost/boost/ratio/ratio.hpp:48:0,
                 from C:/Opt/boost/boost/ratio/include.hpp:11,
                 from C:/Opt/boost/boost/ratio.hpp:12,
                 from test.cpp:2:
C:/Opt/boost/boost/ratio/detail/overflow_helpers.hpp: In instantiation of 'boost::ratio_detail::ratio_add<boost::ratio<0ll>, boost::ratio<0ll> >':
C:/Opt/boost/boost/ratio/ratio.hpp:136:8:   instantiated from 'boost::ratio_add<boost::ratio<0ll>, boost::ratio<0ll> >'
test.cpp:5:39:   instantiated from here
C:/Opt/boost/boost/ratio/detail/overflow_helpers.hpp:243:18: error: '(0ll / 0ll)' is not a constant expression
C:/Opt/boost/boost/ratio/detail/overflow_helpers.hpp:243:18: note: in template argument for type 'long long int' 
test.cpp:5:9: error: 'type' in class 'boost::ratio_add<boost::ratio<0ll>, boost::ratio<0ll> >' does not name a type
In file included from C:/Opt/boost/boost/ratio/ratio.hpp:48:0,
                 from C:/Opt/boost/boost/ratio/include.hpp:11,
                 from C:/Opt/boost/boost/ratio.hpp:12,
                 from test.cpp:2:
C:/Opt/boost/boost/ratio/detail/overflow_helpers.hpp: In instantiation of 'boost::ratio_detail::ratio_subtract<boost::ratio<0ll>, boost::ratio<0ll> >':
C:/Opt/boost/boost/ratio/ratio.hpp:142:8:   instantiated from 'boost::ratio_subtract<boost::ratio<0ll>, boost::ratio<0ll> >'
test.cpp:6:44:   instantiated from here
C:/Opt/boost/boost/ratio/detail/overflow_helpers.hpp:269:18: error: '(0ll / 0ll)' is not a constant expression
C:/Opt/boost/boost/ratio/detail/overflow_helpers.hpp:269:18: note: in template argument for type 'long long int' 
test.cpp:6:9: error: 'type' in class 'boost::ratio_subtract<boost::ratio<0ll>, boost::ratio<0ll> >' does not name a type

[viboes]

(In [73918]) ratio: fix #5724: 0 + 0 and 0 - 0 lead to a compile time error

[viboes]

(In [73919]) ratio: fix #5724: 0 + 0 and 0 - 0 lead to a compile time error

[anonymous]

I have added two partial specialization that solve the issue.

template <class R> struct ratio_add<R, ratio<0> > {

typedef R type;

};

template <class R> struct ratio_subtract<R, ratio<0>> {

typedef R type;

};

to the file boost/ratio/detail/overflow_helpers.hpp.

Sorry for the late replay. Thanks for catching this.

I have committed this and two test on trunk: Committed revision 73918. Committed revision 73919.

[iorate <iorate_stage@…>]

The solution doesn't work with ratio<0, 2> and so on, I think. The following is better:

template <class R, boost::intmax_t D> struct ratio_add<R, ratio<0, D> > {

    typedef R type;

};

template <class R, boost::intmax_t D> struct ratio_subtract<R, ratio<0, D> > {

    typedef R type;

};

[viboes]

Hi, to late replying to your comments :(

I will try to put this in the release, bit it would be easier if you can post the issue on the ML.

Fixed in trunk

Committed revision 75240.