boost/histogram/detail/accumulator_traits.hpp

   1 // Copyright 2019 Hans Dembinski
   2 //
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE_1_0.txt
   5 // or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BOOST_HISTOGRAM_DETAIL_ACCUMULATOR_TRAITS_HPP
   8 #define BOOST_HISTOGRAM_DETAIL_ACCUMULATOR_TRAITS_HPP
   9
  10 #include <boost/histogram/fwd.hpp>
  11 #include <tuple>
  12 #include <type_traits>
  13
  14 namespace boost {
  15
  16 namespace accumulators {
  17 template <class, class, class>
  18 struct accumulator_set;
  19 }
  20
  21 namespace histogram {
  22 namespace detail {
  23
  24 template <bool WeightSupport, class... Ts>
  25 struct accumulator_traits_holder {
  26   using wsupport = std::integral_constant<bool, WeightSupport>;
  27   using args = std::tuple<Ts...>;
  28 };
  29
  30 template <class R, class T, class U, class... Ts>
  31 accumulator_traits_holder<true, Ts...> accumulator_traits_impl_2(
  32     R (T::*)(boost::histogram::weight_type<U>, Ts...));
  33
  34 template <class R, class T, class U, class... Ts>
  35 accumulator_traits_holder<true, Ts...> accumulator_traits_impl_2(
  36     R (T::*)(boost::histogram::weight_type<U>&&, Ts...));
  37
  38 template <class R, class T, class U, class... Ts>
  39 accumulator_traits_holder<true, Ts...> accumulator_traits_impl_2(
  40     R (T::*)(const boost::histogram::weight_type<U>&, Ts...));
  41
  42 template <class R, class T, class... Ts>
  43 accumulator_traits_holder<false, Ts...> accumulator_traits_impl_2(R (T::*)(Ts...));
  44
  45 template <class T>
  46 auto accumulator_traits_impl(T&)
  47     -> decltype(std::declval<T&>() += 0, accumulator_traits_holder<true>{});
  48
  49 template <class T>
  50 auto accumulator_traits_impl(T&) -> decltype(accumulator_traits_impl_2(&T::operator()));
  51
  52 // for boost.accumulators compatibility
  53 template <class S, class F, class W>
  54 accumulator_traits_holder<false, S> accumulator_traits_impl(
  55     boost::accumulators::accumulator_set<S, F, W>&);
  56
  57 template <class T>
  58 using accumulator_traits = decltype(accumulator_traits_impl(std::declval<T&>()));
  59
  60 } // namespace detail
  61 } // namespace histogram
  62 } // namespace boost
  63
  64 #endif