[base] Implemented EqualsBy.

base/base_tests/stl_helpers_test.cpp

@@ -19,30 +19,45 @@ private:
   int m_v;
 };
 
-UNIT_TEST(CompareBy_Field)
+UNIT_TEST(LessBy)
 {
-  vector<pair<int, int>> v = {{2, 2}, {0, 4}, {3, 1}, {4, 0}, {1, 3}};
-  sort(v.begin(), v.end(), my::CompareBy(&pair<int, int>::first));
-  for (size_t i = 0; i < v.size(); ++i)
-    TEST_EQUAL(i, v[i].first, ());
+  using TValue = pair<int, int>;
 
-  vector<pair<int, int> const *> pv;
-  for (auto const & p : v)
-    pv.push_back(&p);
+  {
+    vector<TValue> v = {{2, 2}, {0, 4}, {3, 1}, {4, 0}, {1, 3}};
+    sort(v.begin(), v.end(), my::LessBy(&TValue::first));
+    for (size_t i = 0; i < v.size(); ++i)
+      TEST_EQUAL(i, v[i].first, ());
 
-  sort(pv.begin(), pv.end(), my::CompareBy(&pair<int, int>::second));
-  for (size_t i = 0; i < pv.size(); ++i)
-    TEST_EQUAL(i, pv[i]->second, ());
+    vector<TValue const *> pv;
+    for (auto const & p : v)
+      pv.push_back(&p);
+
+    sort(pv.begin(), pv.end(), my::LessBy(&TValue::second));
+    for (size_t i = 0; i < pv.size(); ++i)
+      TEST_EQUAL(i, pv[i]->second, ());
+  }
+
+  {
+    vector<Int> v;
+    for (int i = 9; i >= 0; --i)
+      v.emplace_back(i);
+
+    sort(v.begin(), v.end(), my::LessBy(&Int::Get));
+    for (size_t i = 0; i < v.size(); ++i)
+      TEST_EQUAL(v[i].Get(), static_cast<int>(i), ());
+  }
 }
 
-UNIT_TEST(CompareBy_Method)
+UNIT_TEST(EqualsBy)
 {
-  vector<Int> v;
-  for (int i = 9; i >= 0; --i)
-    v.emplace_back(i);
+  using TValue = pair<int, int>;
+  vector<TValue> actual = {{1, 2}, {1, 3}, {2, 100}, {3, 7}, {3, 8}, {2, 500}};
+  actual.erase(unique(actual.begin(), actual.end(), my::EqualsBy(&TValue::first)), actual.end());
 
-  sort(v.begin(), v.end(), my::CompareBy(&Int::Get));
-  for (size_t i = 0; i < v.size(); ++i)
-    TEST_EQUAL(v[i].Get(), static_cast<int>(i), ());
+  vector<int> expected = {{1, 2, 3, 2}};
+  TEST_EQUAL(expected.size(), actual.size(), ());
+  for (size_t i = 0; i < actual.size(); ++i)
+    TEST_EQUAL(expected[i], actual[i].first, ());
 }
 }  // namespace

base/stl_helpers.hpp

@@ -7,15 +7,16 @@ namespace my
 {
 namespace impl
 {
-// When isField is true, Comparer operates on a pointers-to-field.
-// Otherwise, Comparer operates on a pointers-to-const-method.
+// When isField is true, following functors operate on a
+// pointers-to-field.  Otherwise, they operate on a
+// pointers-to-const-method.
 template <bool isField, typename T, typename C>
-struct Comparer;
+struct Less;
 
-template<typename T, typename C>
-struct Comparer<true, T, C>
+template <typename T, typename C>
+struct Less<true, T, C>
 {
-  Comparer(T(C::*p)) : p_(p) {}
+  Less(T(C::*p)) : p_(p) {}
 
   inline bool operator()(C const & lhs, C const & rhs) const { return lhs.*p_ < rhs.*p_; }
 
@@ -27,10 +28,10 @@ struct Comparer<true, T, C>
   T(C::*p_);
 };
 
-template<typename T, typename C>
-struct Comparer<false, T, C>
+template <typename T, typename C>
+struct Less<false, T, C>
 {
-  Comparer(T (C::*p)() const) : p_(p) {}
+  Less(T (C::*p)() const) : p_(p) {}
 
   inline bool operator()(C const & lhs, C const & rhs) const { return (lhs.*p_)() < (rhs.*p_)(); }
 
@@ -39,7 +40,40 @@ struct Comparer<false, T, C>
     return (lhs->*p_)() < (rhs->*p_)();
   }
 
-  T(C::*p_)() const;
+  T (C::*p_)() const;
+};
+
+template <bool isField, typename T, typename C>
+struct Equals;
+
+template <typename T, typename C>
+struct Equals<true, T, C>
+{
+  Equals(T(C::*p)) : p_(p) {}
+
+  inline bool operator()(C const & lhs, C const & rhs) const { return lhs.*p_ == rhs.*p_; }
+
+  inline bool operator()(C const * const lhs, C const * const rhs) const
+  {
+    return lhs->*p_ == rhs->*p_;
+  }
+
+  T(C::*p_);
+};
+
+template <typename T, typename C>
+struct Equals<false, T, C>
+{
+  Equals(T (C::*p)() const) : p_(p) {}
+
+  inline bool operator()(C const & lhs, C const & rhs) const { return (lhs.*p_)() == (rhs.*p_)(); }
+
+  inline bool operator()(C const * const lhs, C const * const rhs) const
+  {
+    return (lhs->*p_)() == (rhs->*p_)();
+  }
+
+  T (C::*p_)() const;
 };
 }  // namespace impl
 
@@ -60,17 +94,29 @@ void EraseIf(vector<T> & v, TFn && fn)
 // Creates a comparer being able to compare two instances of class C
 // (given by reference or pointer) by a field or const method of C.
 // For example, to create comparer that is able to compare pairs of
-// ints by second component, it's enough to call CompareBy(&pair<int,
+// ints by second component, it's enough to call LessBy(&pair<int,
 // int>::second).
 template <typename T, typename C>
-impl::Comparer<true, T, C> CompareBy(T(C::*p))
+impl::Less<true, T, C> LessBy(T(C::*p))
 {
-  return impl::Comparer<true, T, C>(p);
+  return impl::Less<true, T, C>(p);
 }
 
 template <typename T, typename C>
-impl::Comparer<false, T, C> CompareBy(T (C::*p)() const)
+impl::Less<false, T, C> LessBy(T (C::*p)() const)
 {
-  return impl::Comparer<false, T, C>(p);
+  return impl::Less<false, T, C>(p);
+}
+
+template <typename T, typename C>
+impl::Equals<true, T, C> EqualsBy(T(C::*p))
+{
+  return impl::Equals<true, T, C>(p);
+}
+
+template <typename T, typename C>
+impl::Equals<false, T, C> EqualsBy(T (C::*p)() const)
+{
+  return impl::Equals<false, T, C>(p);
 }
 }  // namespace my

search/processor.cpp

@@ -510,7 +510,7 @@ void Processor::FlushViewportResults(v2::Geocoder::Params const & params, Result
   if (indV.empty())
     return;
 
-  sort(indV.begin(), indV.end(), my::CompareBy(&IndexedValue::GetDistanceToPivot));
+  sort(indV.begin(), indV.end(), my::LessBy(&IndexedValue::GetDistanceToPivot));
 
   for (size_t i = 0; i < indV.size(); ++i)
   {
@@ -720,7 +720,7 @@ void Processor::FlushResults(v2::Geocoder::Params const & params, Results & res,
   if (indV.empty())
     return;
 
-  sort(indV.rbegin(), indV.rend(), my::CompareBy(&IndexedValue::GetRank));
+  sort(indV.rbegin(), indV.rend(), my::LessBy(&IndexedValue::GetRank));
 
   // Do not process suggestions in additional search.
   if (!allMWMs || res.GetCount() == 0)

search/reverse_geocoder.cpp

@@ -51,7 +51,7 @@ void ReverseGeocoder::GetNearbyStreets(MwmSet::MwmId const & id, m2::PointD cons
   if (mwmHandle.IsAlive())
   {
     search::v2::MwmContext(move(mwmHandle)).ForEachFeature(rect, addStreet);
-    sort(streets.begin(), streets.end(), my::CompareBy(&Street::m_distanceMeters));
+    sort(streets.begin(), streets.end(), my::LessBy(&Street::m_distanceMeters));
   }
 }
 
@@ -174,7 +174,7 @@ void ReverseGeocoder::GetNearbyBuildings(m2::PointD const & center, vector<Build
   };
 
   m_index.ForEachInRect(addBuilding, rect, kQueryScale);
-  sort(buildings.begin(), buildings.end(), my::CompareBy(&Building::m_distanceMeters));
+  sort(buildings.begin(), buildings.end(), my::LessBy(&Building::m_distanceMeters));
 }
 
 // static

search/search_tests/locality_scorer_test.cpp

@@ -98,7 +98,7 @@ public:
   void GetTopLocalities(size_t limit)
   {
     m_scorer.GetTopLocalities(limit, m_localities);
-    sort(m_localities.begin(), m_localities.end(), my::CompareBy(&Geocoder::Locality::m_featureId));
+    sort(m_localities.begin(), m_localities.end(), my::LessBy(&Geocoder::Locality::m_featureId));
   }
 
   // LocalityScorer::Delegate overrides:

search/v2/geocoder.cpp

@@ -1358,7 +1358,7 @@ void Geocoder::FindPaths()
   sortedLayers.reserve(m_layers.size());
   for (auto & layer : m_layers)
     sortedLayers.push_back(&layer);
-  sort(sortedLayers.begin(), sortedLayers.end(), my::CompareBy(&FeaturesLayer::m_type));
+  sort(sortedLayers.begin(), sortedLayers.end(), my::LessBy(&FeaturesLayer::m_type));
 
   auto const & innermostLayer = *sortedLayers.front();