Backport of some concepts from util to C++17

benchmark/BenchmarkExamples.cpp

@@ -56,7 +56,7 @@ class ConfigOptions : public BenchmarkInterface {
     auto numSigns =
         manager.addOption("num-signs", "The number of street signs.",
                           &numberOfStreetSigns_, 10000);
-    manager.addValidator([](const int& num) { return num >= 0; },
+    manager.addValidator([](const int& num) -> bool { return num >= 0; },
                          "The number of street signs must be at least 0!",
                          "Negative numbers, or floating point numbers, are not "
                          "allowed for the configuration option \"num-signs\".",

benchmark/infrastructure/BenchmarkMeasurementContainer.h

@@ -227,8 +227,8 @@ class ResultTable : public BenchmarkMetadataGetter {
 
   @param row, column Which table entry to read. Starts with `(0,0)`.
   */
-  template <ad_utility::SameAsAnyTypeIn<EntryType> T>
-  T getEntry(const size_t row, const size_t column) const {
+  CPP_template(typename T)(requires ad_utility::SameAsAnyTypeIn<T, EntryType>) T
+      getEntry(const size_t row, const size_t column) const {
     AD_CONTRACT_CHECK(row < numRows() && column < numColumns());
     static_assert(!ad_utility::isSimilar<T, std::monostate>);
 

benchmark/infrastructure/BenchmarkToJson.cpp

@@ -31,12 +31,12 @@ provided translation function for the vector entries.
 @tparam TranslationFunction Has to be a function, that takes `VectorType`
 and returns a `nlohmann:json` object.
 */
-template <typename VectorType, ad_utility::InvocableWithExactReturnType<
-                                   nlohmann::ordered_json, VectorType>
-                                   TranslationFunction>
-static nlohmann::json transformIntoJsonArray(
-    const std::vector<VectorType>& vec,
-    TranslationFunction translationFunction) {
+CPP_template(typename VectorType, typename TranslationFunction)(
+    requires ad_utility::InvocableWithExactReturnType<
+        TranslationFunction, nlohmann::ordered_json,
+        VectorType>) static nlohmann::json
+    transformIntoJsonArray(const std::vector<VectorType>& vec,
+                           TranslationFunction translationFunction) {
   /*
   Without explicit instantiation, `nlohmann::nlohmann::ordered_json` is not
   guaranteed, to always interpret a `push_back` correctly. For instance,

src/backports/concepts.h

@@ -35,9 +35,11 @@
 #ifdef QLEVER_CPP_17
 #define QL_CONCEPT_OR_NOTHING(...)
 #define QL_CONCEPT_OR_TYPENAME(...) typename
+#define CPP_and_def CPP_and_sfinae_def
 #else
 #define QL_CONCEPT_OR_NOTHING(...) __VA_ARGS__
 #define QL_CONCEPT_OR_TYPENAME(...) __VA_ARGS__
+#define CPP_and_def CPP_and
 #endif
 
 // The namespace `ql::concepts` includes concepts that are contained in the

src/engine/idTable/IdTableRow.h

@@ -381,8 +381,10 @@ class RowReference
   // The `cbegin` and `cend` functions are implicitly inherited from `Base`.
 
   // __________________________________________________________________________
-  template <ad_utility::SimilarTo<RowReference> R>
-  friend void swap(R&& a, R&& b) requires(!isConst) {
+  CPP_template(typename R)(
+      requires ad_utility::SimilarTo<RowReference, R>) friend void swap(R&& a,
+                                                                        R&& b)
+      requires(!isConst) {
     return Base::swapImpl(AD_FWD(a), AD_FWD(b));
   }
 

src/global/Pattern.h

@@ -13,6 +13,7 @@
 #include <vector>
 
 #include "global/Id.h"
+#include "backports/concepts.h"
 #include "util/ExceptionHandling.h"
 #include "util/File.h"
 #include "util/Generator.h"
@@ -71,6 +72,27 @@ struct CompactStringVectorWriter;
 
 }
 
+#ifdef QLEVER_CPP_17
+template <typename T, typename = void>
+struct IsIteratorOfIterator : std::false_type {};
+
+template <typename T>
+struct IsIteratorOfIterator<
+    T, std::void_t<decltype(*(T::iterator::value_type::begin()))>>
+    : std::true_type {};
+
+template <typename T, typename DataType>
+CPP_concept IteratorOfIterator = 
+    (IsIteratorOfIterator<T>::value &&
+     ad_utility::SimilarTo<decltype(*(T::iterator::value_type::begin())),
+                           DataType>);
+#else
+template <typename T, typename DataType>
+concept IteratorOfIterator = requires(T t) {
+  { *(t.begin()->begin()) } -> ad_utility::SimilarTo<DataType>;
+};
+#endif
+
 /**
  * @brief Stores a list of variable length data of a single type (e.g.
  *        c-style strings). The data is stored in a single contiguous block
@@ -102,10 +124,8 @@ class CompactVectorOfStrings {
    * @brief Fills this CompactVectorOfStrings with input.
    * @param The input from which to build the vector.
    */
-  template <typename T>
-  requires requires(T t) {
-    { *(t.begin()->begin()) } -> ad_utility::SimilarTo<data_type>;
-  } void build(const T& input) {
+  CPP_template(typename T)(
+      requires IteratorOfIterator<T, data_type>) void build(const T& input) {
     // Also make room for the end offset of the last element.
     _offsets.reserve(input.size() + 1);
     size_t dataSize = 0;

src/index/CompressedRelation.cpp

@@ -752,13 +752,14 @@ size_t CompressedRelationReader::getResultSizeOfScan(
 }
 
 // ____________________________________________________________________________
-IdTable CompressedRelationReader::getDistinctColIdsAndCountsImpl(
-    ad_utility::InvocableWithConvertibleReturnType<
-        Id, const CompressedBlockMetadata::PermutedTriple&> auto idGetter,
-    const ScanSpecification& scanSpec,
-    const std::vector<CompressedBlockMetadata>& allBlocksMetadata,
-    const CancellationHandle& cancellationHandle,
-    const LocatedTriplesPerBlock& locatedTriplesPerBlock) const {
+CPP_template_def(typename IdGetter)(
+    requires ad_utility::InvocableWithConvertibleReturnType<
+        IdGetter, Id, const CompressedBlockMetadata::PermutedTriple&>) IdTable
+    CompressedRelationReader::getDistinctColIdsAndCountsImpl(
+        IdGetter idGetter, const ScanSpecification& scanSpec,
+        const std::vector<CompressedBlockMetadata>& allBlocksMetadata,
+        const CancellationHandle& cancellationHandle,
+        const LocatedTriplesPerBlock& locatedTriplesPerBlock) const {
   // The result has two columns: one for the distinct `Id`s and one for their
   // counts.
   IdTableStatic<2> table(allocator_);

src/index/CompressedRelation.h

@@ -746,13 +746,14 @@ class CompressedRelationReader {
 
   // The common implementation for `getDistinctCol0IdsAndCounts` and
   // `getCol1IdsAndCounts`.
-  IdTable getDistinctColIdsAndCountsImpl(
-      ad_utility::InvocableWithConvertibleReturnType<
-          Id, const CompressedBlockMetadata::PermutedTriple&> auto idGetter,
-      const ScanSpecification& scanSpec,
-      const std::vector<CompressedBlockMetadata>& allBlocksMetadata,
-      const CancellationHandle& cancellationHandle,
-      const LocatedTriplesPerBlock& locatedTriplesPerBlock) const;
+  CPP_template(typename IdGetter)(
+      requires ad_utility::InvocableWithConvertibleReturnType<
+          IdGetter, Id, const CompressedBlockMetadata::PermutedTriple&>) IdTable
+      getDistinctColIdsAndCountsImpl(
+          IdGetter idGetter, const ScanSpecification& scanSpec,
+          const std::vector<CompressedBlockMetadata>& allBlocksMetadata,
+          const CancellationHandle& cancellationHandle,
+          const LocatedTriplesPerBlock& locatedTriplesPerBlock) const;
 };
 
 // TODO<joka921>

src/index/StringSortComparator.h

@@ -51,8 +51,8 @@ class LocaleManager {
   using U8String = std::basic_string<uint8_t>;
   using U8StringView = std::basic_string_view<uint8_t>;
 
-  template <ad_utility::SimilarToAny<U8String, U8StringView> T>
-  class SortKeyImpl {
+  CPP_template(typename T)(requires ad_utility::SimilarToAny<
+                           T, U8String, U8StringView>) class SortKeyImpl {
    public:
     SortKeyImpl() = default;
     explicit SortKeyImpl(U8StringView sortKey) : sortKey_(sortKey) {}

src/util/Algorithm.h

@@ -58,8 +58,10 @@ bool contains_if(const Container& container, const Predicate& predicate) {
  * @param destination Vector& to which to append
  * @param source Vector&& to append
  */
-template <typename T, ad_utility::SimilarTo<std::vector<T>> U>
-void appendVector(std::vector<T>& destination, U&& source) {
+CPP_template(typename T, typename U)(
+    requires ad_utility::SimilarTo<
+        std::vector<T>, U>) void appendVector(std::vector<T>& destination,
+                                              U&& source) {
   destination.insert(destination.end(),
                      ad_utility::makeForwardingIterator<U>(source.begin()),
                      ad_utility::makeForwardingIterator<U>(source.end()));

src/util/CancellationHandle.h

@@ -156,10 +156,14 @@ class CancellationHandle {
   /// in the console that would otherwise be triggered by the watchdog.
   /// NOTE: The parameter state is expected to be one of `CHECK_WINDOW_MISSED`
   /// or `WAITING_FOR_CHECK`, otherwise it will violate the correctness check.
-  void pleaseWatchDog(CancellationState state,
-                      ad_utility::source_location location,
-                      const ad_utility::InvocableWithConvertibleReturnType<
-                          std::string_view> auto& stageInvocable)
+  CPP_template(typename StateFunc)(
+      requires ad_utility::InvocableWithConvertibleReturnType<
+          StateFunc,
+          std::string_view>) void pleaseWatchDog(CancellationState state,
+                                                 ad_utility::source_location
+                                                     location,
+                                                 const StateFunc&
+                                                     stageInvocable)
       requires WatchDogEnabled {
     using DurationType =
         std::remove_const_t<decltype(DESIRED_CANCELLATION_CHECK_INTERVAL)>;
@@ -215,12 +219,13 @@ class CancellationHandle {
   /// nothing otherwise. If `WatchDogEnabled` is true, this will log a warning
   /// if this check is not called frequently enough. It will contain the
   /// filename and line of the caller of this method.
-  template <ad_utility::InvocableWithConvertibleReturnType<std::string_view>
-                Func = decltype(detail::printNothing)>
-  AD_ALWAYS_INLINE void throwIfCancelled(
-      [[maybe_unused]] ad_utility::source_location location =
-          ad_utility::source_location::current(),
-      const Func& stageInvocable = detail::printNothing) {
+  CPP_template(typename Func = decltype(detail::printNothing))(
+      requires ad_utility::InvocableWithConvertibleReturnType<Func,
+                                                              std::string_view>)
+      AD_ALWAYS_INLINE void throwIfCancelled(
+          [[maybe_unused]] ad_utility::source_location location =
+              ad_utility::source_location::current(),
+          const Func& stageInvocable = detail::printNothing) {
     if constexpr (CancellationEnabled) {
       auto state = cancellationState_.load(std::memory_order_relaxed);
       if (state == CancellationState::NOT_CANCELLED) [[likely]] {