mirror of
https://github.com/jezhiggins/arabica
synced 2024-12-27 21:58:30 +01:00
45 lines
972 B
C++
45 lines
972 B
C++
#ifndef ARABICA_UTILS_GET_PARAM_HPP
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#define ARABICA_UTILS_GET_PARAM_HPP
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#ifdef HAVE_BOOST
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#include <boost/mpl/if.hpp>
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#include <boost/type_traits/is_base_and_derived.hpp>
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#endif
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namespace Arabica
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{
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struct nil_t { };
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#ifdef HAVE_BOOST
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template <typename BaseT, typename DefaultT, typename T0, typename T1>
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struct get_param
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{
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typedef typename boost::mpl::if_<
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boost::is_base_and_derived<BaseT, T0>
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, T0
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, typename boost::mpl::if_<
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boost::is_base_and_derived<BaseT, T1>
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, T1
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, DefaultT
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>::type
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>::type type;
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}; // get_param
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#else
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template <typename T0, typename DefaultT>
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struct chosen_type { typedef T0 type; };
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template <typename DefaultT>
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struct chosen_type<Arabica::nil_t, DefaultT> { typedef DefaultT type; };
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template <typename BaseT, typename DefaultT, typename T0, typename T1>
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struct get_param
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{
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typedef typename chosen_type<T0, DefaultT>::type type;
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};
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#endif
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} // namespace Arabica
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#endif
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