type_traits.h

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#ifndef fhiclcpp_type_traits_h
#define fhiclcpp_type_traits_h
// ======================================================================
//
// type traits
//
// ======================================================================

#include "cetlib/metaprogramming.h"

#include <array>
#include <complex>
#include <set>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

// ======================================================================

namespace fhicl {

  template <typename T>
  class Atom;
  template <typename T>
  class OptionalAtom;

  template <typename T, typename KeysToIgnore>
  class Table;
  template <typename T>
  class OptionalTable;

  template <typename T>
  class TableFragment;

  template <typename... ARGS>
  class Tuple;
  template <typename... ARGS>
  class OptionalTuple;

  template <typename T, std::size_t SZ>
  class Sequence;
  template <typename T, std::size_t SZ>
  class OptionalSequence;

  template <typename T, typename... ARGS>
  class TupleAs;
  template <typename T, typename... ARGS>
  class OptionalTupleAs;

  class DelegatedParameter;
  class OptionalDelegatedParameter;
}

namespace tt {

  using cet::enable_if_function_exists_t;
  using std::enable_if;
  using std::is_floating_point;

  template <bool b, typename T = void>
  using disable_if = std::enable_if<!b, T>;

  template <typename T>
  struct is_int : std::integral_constant<bool,
                                         std::is_integral<T>::value &&
                                           !std::is_unsigned<T>::value> {};

  template <typename T>
  using is_numeric = std::is_arithmetic<T>;

  template <typename T>
  using is_uint = std::is_unsigned<T>;

  template <typename T, typename = void>
  struct is_callable : std::false_type {};

  template <typename T>
  struct is_callable<
    T,
    enable_if_function_exists_t<std::set<std::string> (T::*)(), &T::operator()>>
    : std::true_type {};

  template <typename T>
  struct is_callable<
    T,
    enable_if_function_exists_t<std::set<std::string> (T::*)() const,
                                &T::operator()>> : std::true_type {};

  //=======================================================
  // Enforce (non)const-ness
  //
  enum class const_flavor { require_non_const, require_const };

  template <typename T, const_flavor C>
  struct maybe_const {
    using type = T;
  };

  template <typename T>
  struct maybe_const<T, const_flavor::require_const> {
    using type = std::add_const_t<T>;
  };

  template <typename T, const_flavor C>
  using maybe_const_t = typename maybe_const<T, C>::type;

  //=======================================================
  // Check if sequence type
  //
  template <typename Container>
  struct is_sequence_type : std::false_type {};

  template <typename ARG, std::size_t SZ>
  struct is_sequence_type<std::array<ARG, SZ>> : std::true_type {};
  template <typename... ARGS>
  struct is_sequence_type<std::tuple<ARGS...>> : std::true_type {};
  template <typename... ARGS>
  struct is_sequence_type<std::vector<ARGS...>> : std::true_type {};

  //=======================================================
  // Check if Table<>
  //
  template <typename T>
  struct is_table : std::false_type {};

  template <typename T, typename KeysToIgnore>
  struct is_table<fhicl::Table<T, KeysToIgnore>> : std::true_type {};

  //=======================================================
  // Check if TableFragment<>
  //
  template <typename T>
  struct is_table_fragment : std::false_type {};

  template <typename T>
  struct is_table_fragment<fhicl::TableFragment<T>> : std::true_type {};

  //=======================================================
  // Check if optional parameter
  //
  template <typename T>
  struct is_optional_parameter : std::false_type {};

  template <typename T>
  struct is_optional_parameter<fhicl::OptionalTable<T>> : std::true_type {};

  template <typename T>
  struct is_optional_parameter<fhicl::OptionalAtom<T>> : std::true_type {};

  template <typename T, std::size_t SZ>
  struct is_optional_parameter<fhicl::OptionalSequence<T, SZ>>
    : std::true_type {};

  template <typename... TYPES>
  struct is_optional_parameter<fhicl::OptionalTuple<TYPES...>>
    : std::true_type {};

  template <typename T, typename... ARGS>
  struct is_optional_parameter<fhicl::OptionalTupleAs<T(ARGS...)>>
    : std::true_type {};

  //=======================================================
  // Check if delegated parameter
  //
  template <typename T>
  struct is_delegated_parameter : std::false_type {};

  template <>
  struct is_delegated_parameter<fhicl::DelegatedParameter> : std::true_type {};

  template <>
  struct is_delegated_parameter<fhicl::OptionalDelegatedParameter>
    : std::true_type {};

  //=======================================================
  // Check if fhicl type -- i.e. Atom<>, Table<>, etc.
  //
  template <typename T>
  struct is_fhicl_type : std::false_type {};

  // ... Table
  template <typename T, typename KeysToIgnore>
  struct is_fhicl_type<fhicl::Table<T, KeysToIgnore>> : std::true_type {};

  template <typename T>
  struct is_fhicl_type<fhicl::OptionalTable<T>> : std::true_type {};

  // ... Atom
  template <typename T>
  struct is_fhicl_type<fhicl::Atom<T>> : std::true_type {};

  template <typename T>
  struct is_fhicl_type<fhicl::OptionalAtom<T>> : std::true_type {};

  // ... Sequence
  template <typename T, std::size_t SZ>
  struct is_fhicl_type<fhicl::Sequence<T, SZ>> : std::true_type {};

  template <typename T, std::size_t SZ>
  struct is_fhicl_type<fhicl::OptionalSequence<T, SZ>> : std::true_type {};

  // ... Tuple
  template <typename... TYPES>
  struct is_fhicl_type<fhicl::Tuple<TYPES...>> : std::true_type {};

  template <typename... TYPES>
  struct is_fhicl_type<fhicl::OptionalTuple<TYPES...>> : std::true_type {};

  // ... TupleAs
  template <typename T, typename... ARGS>
  struct is_fhicl_type<fhicl::TupleAs<T(ARGS...)>> : std::true_type {};

  template <typename T, typename... ARGS>
  struct is_fhicl_type<fhicl::OptionalTupleAs<T(ARGS...)>> : std::true_type {};

  //=======================================================
  // Get FHiCL types: can be Atom, Sequence, Tuple, or Table
  //
  template <typename T>
  struct fhicl_type_impl {
    using type = fhicl::Atom<T>;
  };

  template <typename T, std::size_t SZ>
  struct fhicl_type_impl<fhicl::Sequence<T, SZ>> {
    using type = fhicl::Sequence<T, SZ>;
  };

  template <typename T, typename KeysToIgnore>
  struct fhicl_type_impl<fhicl::Table<T, KeysToIgnore>> {
    using type = fhicl::Table<T, KeysToIgnore>;
  };

  template <typename... ARGS>
  struct fhicl_type_impl<fhicl::Tuple<ARGS...>> {
    using type = fhicl::Tuple<ARGS...>;
  };

  template <typename T, typename... ARGS>
  struct fhicl_type_impl<fhicl::TupleAs<T(ARGS...)>> {
    using type = fhicl::TupleAs<T(ARGS...)>;
  };

  template <typename T>
  struct fhicl_type_impl<fhicl::OptionalAtom<T>> {
    using type = fhicl::OptionalAtom<T>;
  };

  template <typename T, std::size_t SZ>
  struct fhicl_type_impl<fhicl::OptionalSequence<T, SZ>> {
    using type = fhicl::OptionalSequence<T, SZ>;
  };

  template <typename T>
  struct fhicl_type_impl<fhicl::OptionalTable<T>> {
    using type = fhicl::OptionalTable<T>;
  };

  template <typename... ARGS>
  struct fhicl_type_impl<fhicl::OptionalTuple<ARGS...>> {
    using type = fhicl::OptionalTuple<ARGS...>;
  };

  template <typename T, typename... ARGS>
  struct fhicl_type_impl<fhicl::OptionalTupleAs<T(ARGS...)>> {
    using type = fhicl::OptionalTupleAs<T(ARGS...)>;
  };

  // The alias
  template <typename T>
  using fhicl_type = typename fhicl_type_impl<T>::type;

  //=======================================================
  // Get Return types
  //
  template <typename T>
  struct return_type_impl {
    using value_type = T;
  };

  template <typename T>
  struct return_type_impl<fhicl::Atom<T>> {
    using value_type = typename fhicl::Atom<T>::value_type;
  };

  template <typename T, std::size_t SZ>
  struct return_type_impl<fhicl::Sequence<T, SZ>> {
    using value_type = typename fhicl::Sequence<T, SZ>::value_type;
  };

  template <typename S, typename KeysToIgnore>
  struct return_type_impl<fhicl::Table<S, KeysToIgnore>> {
    using value_type = typename fhicl::Table<S, KeysToIgnore>::value_type;
  };

  template <typename... ARGS>
  struct return_type_impl<fhicl::Tuple<ARGS...>> {
    using value_type = typename fhicl::Tuple<ARGS...>::value_type;
  };

  template <typename T, typename... ARGS>
  struct return_type_impl<fhicl::TupleAs<T(ARGS...)>> {
    using value_type = typename fhicl::TupleAs<T(ARGS...)>::value_type;
  };

  // The alias
  template <typename... ARGS>
  using return_type = typename return_type_impl<ARGS...>::value_type;
}

#endif /* fhiclcpp_type_traits_h */

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