deduce_hp_types.hpp

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#ifndef MLPACK_CORE_HPT_DEDUCE_HP_TYPES_HPP
#define MLPACK_CORE_HPT_DEDUCE_HP_TYPES_HPP

#include <mlpack/core/hpt/fixed.hpp>

namespace mlpack {
namespace hpt {

template<typename... Args>
struct DeduceHyperParameterTypes
{
  template<typename... HPTypes>
  struct ResultHolder
  {
    using TupleType = std::tuple<HPTypes...>;
  };
};

template<typename T, typename... Args>
struct DeduceHyperParameterTypes<T, Args...>
{
  template<typename ArgumentType,
           bool IsArithmetic = std::is_arithmetic<ArgumentType>::value>
  struct ResultHPType;

  template<typename ArithmeticType>
  struct ResultHPType<ArithmeticType, true>
  {
    using Type = ArithmeticType;
  };

  template<typename Type>
  struct IsCollectionType
  {
    using Yes = char[1];
    using No = char[2];

    template<typename TypeToCheck>
    static Yes& Check(typename TypeToCheck::value_type*);
    template<typename>
    static No& Check(...);

    static const bool value  =
      sizeof(decltype(Check<Type>(0))) == sizeof(Yes);
  };

  template<typename CollectionType>
  struct ResultHPType<CollectionType, false>
  {
    static_assert(IsCollectionType<CollectionType>::value,
        "One of the passed arguments is neither of an arithmetic type, nor of "
        "a collection type, nor fixed with the Fixed function.");

    using Type = typename CollectionType::value_type;
  };

  template<typename... HPTypes>
  struct ResultHolder
  {
    using TupleType = typename DeduceHyperParameterTypes<Args...>::template
        ResultHolder<HPTypes..., typename ResultHPType<T>::Type>::TupleType;
  };

  using TupleType = typename ResultHolder<>::TupleType;
};

template<typename T, typename... Args>
struct DeduceHyperParameterTypes<PreFixedArg<T>, Args...>
{
  template<typename... HPTypes>
  struct ResultHolder
  {
    using TupleType = typename DeduceHyperParameterTypes<Args...>::template
        ResultHolder<HPTypes...>::TupleType;
  };

  using TupleType = typename ResultHolder<>::TupleType;
};

template<typename... Args>
using TupleOfHyperParameters =
    typename DeduceHyperParameterTypes<Args...>::TupleType;

} // namespace hpt
} // namespace mlpack

#endif