Pick Variant from Standalone Maybe

cmake/oneflow.cmake

@@ -174,7 +174,7 @@ foreach(oneflow_single_file ${oneflow_all_src})
     continue()
   endif()
 
-  if("${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/(core|user|xrt)/.*\\.(h|hpp)$")
+  if("${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/(core|user|xrt|maybe)/.*\\.(h|hpp)$")
     if((NOT RPC_BACKEND MATCHES "GRPC") AND "${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/core/control/.*")
       # skip if GRPC not enabled
     elseif(APPLE AND "${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/core/comm_network/(epoll|ibverbs)/.*")
@@ -228,8 +228,8 @@ foreach(oneflow_single_file ${oneflow_all_src})
 
   endif(BUILD_PYTHON)
 
-  if("${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/(core|user|xrt)/.*\\.cpp$")
-    if("${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/(core|user|xrt)/.*_test\\.cpp$")
+  if("${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/(core|user|xrt|maybe)/.*\\.cpp$")
+    if("${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/(core|user|xrt|maybe)/.*_test\\.cpp$")
       # test file
       list(APPEND of_all_test_cc ${oneflow_single_file})
     elseif(APPLE AND "${oneflow_single_file}" MATCHES "^${PROJECT_SOURCE_DIR}/oneflow/core/comm_network/(epoll|ibverbs)/.*")

oneflow/maybe/config.h

@@ -0,0 +1,52 @@
+/*
+Copyright 2020 The OneFlow Authors. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#ifndef ONEFLOW_MAYBE_CONFIG_H_
+#define ONEFLOW_MAYBE_CONFIG_H_
+
+#include <cassert>
+
+// pre-define it if you use a logging library like glog
+#ifndef OF_MAYBE_ASSERT
+#define OF_MAYBE_ASSERT(_cond_) assert(_cond_)
+#endif
+
+// ASSERT_EQ is different from ASSERT in logging / testing framework
+// pre-define it if you use a logging library like glog
+#ifndef OF_MAYBE_ASSERT_EQ
+#define OF_MAYBE_ASSERT_EQ(_lhs_, _rhs_) OF_MAYBE_ASSERT(_lhs_ == _rhs_)
+#endif
+
+#if __GNUC__ >= 7
+#define OF_MAYBE_HAS_IS_AGGREGATE
+// in old versions of clang, __has_builtin(__is_aggregate) returns false
+#elif __clang__
+#if !__is_identifier(__is_aggregate)
+#define OF_MAYBE_HAS_IS_AGGREGATE
+#endif
+#elif __has_builtin(__is_aggregate)
+#define OF_MAYBE_HAS_IS_AGGREGATE
+#endif
+
+#ifdef OF_MAYBE_HAS_IS_AGGREGATE
+#define OF_MAYBE_IS_AGGREGATE(...) __is_aggregate(__VA_ARGS__)
+#else
+// decay to POD checking if no such builtin (because implementing __is_aggregate need reflection)
+#define OF_MAYBE_IS_AGGREGATE(...) \
+  std::is_standard_layout<__VA_ARGS__>::value&& std::is_trivial<__VA_ARGS__>::value
+#endif
+
+#endif  // ONEFLOW_MAYBE_CONFIG_H_

oneflow/maybe/type_traits.h

@@ -0,0 +1,152 @@
+/*
+Copyright 2020 The OneFlow Authors. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#ifndef ONEFLOW_MAYBE_TYPE_TRAITS_H_
+#define ONEFLOW_MAYBE_TYPE_TRAITS_H_
+
+#include <cstddef>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+#include "config.h"
+
+namespace oneflow {
+
+namespace maybe {
+
+// in this file, xxxS represents struct of xxx
+// for implementant aspect, xxx is an alias of xxxS::type or xxxS::value
+
+template<bool B>
+using BoolConstant = std::integral_constant<bool, B>;
+
+template<std::size_t I>
+using IndexConstant = std::integral_constant<std::size_t, I>;
+
+constexpr std::size_t NPos = -1;
+
+template<typename...>
+struct ConjS : std::true_type {};
+template<typename B1>
+struct ConjS<B1> : B1 {};
+template<typename B1, typename... Bn>
+struct ConjS<B1, Bn...> : std::conditional_t<bool(B1::value), ConjS<Bn...>, B1> {};
+
+template<typename... B>
+constexpr bool Conj = ConjS<B...>::value;
+
+template<typename...>
+struct DisjS : std::false_type {};
+template<typename B1>
+struct DisjS<B1> : B1 {};
+template<typename B1, typename... Bn>
+struct DisjS<B1, Bn...> : std::conditional_t<bool(B1::value), B1, DisjS<Bn...>> {};
+
+template<typename... B>
+constexpr bool Disj = DisjS<B...>::value;
+
+template<typename B>
+struct NegS : BoolConstant<!bool(B::value)> {};
+
+template<typename B>
+constexpr bool Neg = NegS<B>::value;
+
+struct TypeNotFound;
+
+// return TypeNotFound while out of range
+template<std::size_t I, typename... Tn>
+struct TypeGetS;
+
+template<std::size_t I, typename T1, typename... Tn>
+struct TypeGetS<I, T1, Tn...> : TypeGetS<I - 1, Tn...> {};
+
+template<typename T1, typename... Tn>
+struct TypeGetS<0, T1, Tn...> {
+  using type = T1;
+};
+
+template<std::size_t N>
+struct TypeGetS<N> {
+  using type = TypeNotFound;
+};
+
+template<std::size_t I, typename... Ts>
+using TypeGet = typename TypeGetS<I, Ts...>::type;
+
+// return NPos (-1) while not found
+template<std::size_t I, typename T, typename... Tn>
+struct IndexGetFromS;
+
+template<std::size_t I, typename T, typename T1, typename... Tn>
+struct IndexGetFromS<I, T, T1, Tn...> : IndexGetFromS<I + 1, T, Tn...> {};
+
+template<std::size_t I, typename T1, typename... Tn>
+struct IndexGetFromS<I, T1, T1, Tn...> : IndexConstant<I> {};
+
+template<std::size_t I, typename T>
+struct IndexGetFromS<I, T> : IndexConstant<NPos> {};
+
+template<typename T, typename... Ts>
+constexpr auto IndexGet = IndexGetFromS<0, T, Ts...>::value;
+
+template<typename T, typename... Ts>
+constexpr auto TypeIn = IndexGet<T, Ts...> != NPos;
+
+template<typename T, typename... Ts>
+using TypeInS = BoolConstant<TypeIn<T, Ts...>>;
+
+template<typename T>
+struct RemoveCVRefS {
+  using type = std::remove_cv_t<std::remove_reference_t<T>>;
+};
+
+template<typename T>
+using RemoveCVRef = typename RemoveCVRefS<T>::type;
+
+template<typename T, typename... Ts>
+struct IsDifferentTypesS : BoolConstant<!TypeIn<T, Ts...> && IsDifferentTypesS<Ts...>::value> {};
+
+template<typename T>
+struct IsDifferentTypesS<T> : std::true_type {};
+
+template<typename T, typename... Ts>
+constexpr auto IsDifferentTypes = IsDifferentTypesS<T, Ts...>::value;
+
+template<typename T>
+struct ConstRefExceptVoidS {
+  using type = const T&;
+};
+
+template<>
+struct ConstRefExceptVoidS<void> {
+  using type = void;
+};
+
+template<typename T>
+using ConstRefExceptVoid = typename ConstRefExceptVoidS<T>::type;
+
+template<typename T>
+using RemoveRValRef =
+    std::conditional_t<std::is_rvalue_reference<T>::value, std::remove_reference_t<T>, T>;
+
+template<typename T>
+constexpr bool IsAggregate = OF_MAYBE_IS_AGGREGATE(T);
+
+}  // namespace maybe
+
+}  // namespace oneflow
+
+#endif  // ONEFLOW_MAYBE_TYPE_TRAITS_H_

oneflow/maybe/type_traits_test.cpp

@@ -0,0 +1,64 @@
+/*
+Copyright 2020 The OneFlow Authors. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include <gtest/gtest.h>
+#include <type_traits>
+#include "oneflow/maybe/type_traits.h"
+
+using namespace oneflow::maybe;
+
+TEST(TypeTraits, Basics) {
+  static_assert(Conj<std::true_type, std::true_type>, "");
+  static_assert(!Conj<std::false_type, std::true_type>, "");
+  static_assert(!Conj<std::true_type, std::false_type>, "");
+  static_assert(!Conj<std::false_type, std::false_type>, "");
+  static_assert(!Conj<std::true_type, std::true_type, std::false_type>, "");
+
+  static_assert(Disj<std::true_type, std::true_type>, "");
+  static_assert(Disj<std::false_type, std::true_type>, "");
+  static_assert(Disj<std::true_type, std::false_type>, "");
+  static_assert(!Disj<std::false_type, std::false_type>, "");
+  static_assert(Disj<std::true_type, std::true_type, std::false_type>, "");
+  static_assert(!Disj<std::false_type, std::false_type, std::false_type>, "");
+
+  static_assert(std::is_same<TypeGet<0, int>, int>::value, "");
+  static_assert(std::is_same<TypeGet<0, int, float>, int>::value, "");
+  static_assert(std::is_same<TypeGet<1, int, float>, float>::value, "");
+  static_assert(std::is_same<TypeGet<2, int, float, bool, int>, bool>::value, "");
+  static_assert(std::is_same<TypeGet<2, int, int>, TypeNotFound>::value, "");
+  static_assert(std::is_same<TypeGet<2, int, int, float>, float>::value, "");
+  static_assert(std::is_same<TypeGet<2, int, int, float, int>, float>::value, "");
+  static_assert(std::is_same<TypeGet<2>, TypeNotFound>::value, "");
+
+  static_assert(IndexGet<int, int> == 0, "");
+  static_assert(IndexGet<int, float> == NPos, "");
+  static_assert(IndexGet<int, int, int> == 0, "");
+  static_assert(IndexGet<int, float, int> == 1, "");
+  static_assert(IndexGet<bool, int, float, int, bool, bool, int> == 3, "");
+  static_assert(IndexGet<int> == NPos, "");
+
+  static_assert(!TypeIn<int>, "");
+  static_assert(TypeIn<int, int>, "");
+  static_assert(TypeIn<int, float, int>, "");
+  static_assert(!TypeIn<int, float, float, bool>, "");
+  static_assert(TypeIn<int, float, bool, int, float>, "");
+  static_assert(TypeIn<bool, float, float, bool>, "");
+
+  static_assert(IsDifferentTypes<int, float, bool>, "");
+  static_assert(!IsDifferentTypes<int, float, int, bool>, "");
+  static_assert(IsDifferentTypes<int>, "");
+  static_assert(!IsDifferentTypes<int, int>, "");
+}

oneflow/maybe/utility.h

@@ -0,0 +1,89 @@
+/*
+Copyright 2020 The OneFlow Authors. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#ifndef ONEFLOW_MAYBE_UTILITY_H_
+#define ONEFLOW_MAYBE_UTILITY_H_
+
+#include <cstddef>
+#include <functional>
+
+namespace oneflow {
+
+namespace maybe {
+
+// unlike std::nullopt in c++17, the NullOptType is used in both Variant and Optional,
+// so it is more like both std::nullopt and std::monostate (in c++17),
+// the advantage of this unification is a more unifed experience,
+// i.e. `return NullOpt` can be used in both Variant and Optional context
+struct NullOptType {
+  explicit constexpr NullOptType() = default;
+
+  bool operator==(NullOptType) const { return true; }
+  bool operator!=(NullOptType) const { return false; }
+  bool operator<(NullOptType) const { return false; }
+  bool operator>(NullOptType) const { return false; }
+  bool operator<=(NullOptType) const { return true; }
+  bool operator>=(NullOptType) const { return true; }
+};
+
+constexpr const std::size_t NullOptHash = -3333;
+
+constexpr NullOptType NullOpt{};
+
+struct InPlaceT {
+  explicit constexpr InPlaceT() = default;
+};
+
+constexpr InPlaceT InPlace;
+
+template<typename T>
+struct InPlaceTypeT {
+  explicit constexpr InPlaceTypeT() = default;
+};
+
+template<typename T>
+constexpr InPlaceTypeT<T> InPlaceType;
+
+template<std::size_t I>
+struct InPlaceIndexT {
+  explicit constexpr InPlaceIndexT() = default;
+};
+
+template<std::size_t I>
+constexpr InPlaceIndexT<I> InPlaceIndex;
+
+template<class T>
+constexpr void HashCombine(std::size_t& seed, const T& v) {
+  std::hash<T> hasher;
+  seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+}
+
+}  // namespace maybe
+
+}  // namespace oneflow
+
+namespace std {
+
+template<>
+struct hash<oneflow::maybe::NullOptType> {
+  size_t operator()(oneflow::maybe::NullOptType) const noexcept {
+    return oneflow::maybe::NullOptHash;
+  }
+};
+
+}  // namespace std
+
+#endif  // ONEFLOW_MAYBE_UTILITY_H_