Get rid of enable_if in favor of requires

examples/brute_force/example_brute_force.cpp

@@ -67,8 +67,8 @@ struct ArborX::AccessTraits<Dummy>
   }
 };
 
-template <typename View,
-          typename Enable = std::enable_if_t<Kokkos::is_view_v<View>>>
+template <typename View>
+  requires(Kokkos::is_view_v<View>)
 std::ostream &operator<<(std::ostream &os, View const &view)
 {
   auto view_host =

src/cluster/detail/ArborX_CartesianGrid.hpp

@@ -46,8 +46,8 @@ struct CartesianGrid
     buildGrid();
   }
 
-  template <typename Point, typename Enable = std::enable_if_t<
-                                GeometryTraits::is_point_v<Point>>>
+  template <typename Point>
+    requires(GeometryTraits::is_point_v<Point>)
   KOKKOS_FUNCTION size_t cellIndex(Point const &point) const
   {
     static_assert(GeometryTraits::dimension_v<Point> == DIM);

src/distributed/detail/ArborX_DistributedTreeImpl.hpp

@@ -25,20 +25,20 @@ struct DistributedTreeImpl
   // spatial queries
   template <typename DistributedTree, typename ExecutionSpace,
             typename Predicates, typename Values, typename Offset>
-  static std::enable_if_t<Kokkos::is_view_v<Values> &&
-                          Kokkos::is_view_v<Offset>>
-  queryDispatch(SpatialPredicateTag, DistributedTree const &tree,
-                ExecutionSpace const &space, Predicates const &queries,
-                Values &values, Offset &offset);
+    requires(Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>)
+  static void queryDispatch(SpatialPredicateTag, DistributedTree const &tree,
+                            ExecutionSpace const &space,
+                            Predicates const &queries, Values &values,
+                            Offset &offset);
 
   template <typename DistributedTree, typename ExecutionSpace,
             typename Predicates, typename OutputView, typename OffsetView,
             typename Callback>
-  static std::enable_if_t<Kokkos::is_view_v<OutputView> &&
-                          Kokkos::is_view_v<OffsetView>>
-  queryDispatch(SpatialPredicateTag, DistributedTree const &tree,
-                ExecutionSpace const &space, Predicates const &queries,
-                Callback const &callback, OutputView &out, OffsetView &offset);
+    requires(Kokkos::is_view_v<OutputView> && Kokkos::is_view_v<OffsetView>)
+  static void queryDispatch(SpatialPredicateTag, DistributedTree const &tree,
+                            ExecutionSpace const &space,
+                            Predicates const &queries, Callback const &callback,
+                            OutputView &out, OffsetView &offset);
 
   template <typename DistributedTree, typename ExecutionSpace,
             typename Predicates, typename Callback>
@@ -59,16 +59,16 @@ struct DistributedTreeImpl
 
   template <typename DistributedTree, typename ExecutionSpace,
             typename Predicates, typename Values, typename Offset>
-  static std::enable_if_t<Kokkos::is_view_v<Values> &&
-                          Kokkos::is_view_v<Offset>>
+    requires(Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>)
+  static void
   queryDispatch(NearestPredicateTag tag, DistributedTree const &tree,
                 ExecutionSpace const &space, Predicates const &queries,
                 Values &values, Offset &offset);
 
   template <typename Tree, typename ExecutionSpace, typename Predicates,
             typename Callback, typename Values, typename Offset>
-  static std::enable_if_t<Kokkos::is_view_v<Values> &&
-                          Kokkos::is_view_v<Offset>>
+    requires(Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>)
+  static void
   queryDispatch(NearestPredicateTag, Tree const &tree,
                 ExecutionSpace const &space, Predicates const &predicates,
                 Callback const &callback, Values &values, Offset &offset);

src/distributed/detail/ArborX_DistributedTreeNearest.hpp

@@ -217,24 +217,25 @@ void DistributedTreeImpl::queryDispatch2RoundImpl(
 
 template <typename Tree, typename ExecutionSpace, typename Predicates,
           typename Values, typename Offset>
-std::enable_if_t<Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>>
-DistributedTreeImpl::queryDispatch(NearestPredicateTag tag, Tree const &tree,
-                                   ExecutionSpace const &space,
-                                   Predicates const &predicates, Values &values,
-                                   Offset &offset)
+  requires(Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>)
+void DistributedTreeImpl::queryDispatch(NearestPredicateTag tag,
+                                        Tree const &tree,
+                                        ExecutionSpace const &space,
+                                        Predicates const &predicates,
+                                        Values &values, Offset &offset)
 {
   queryDispatch2RoundImpl(tag, tree, space, predicates, DefaultCallback{},
                           values, offset);
 }
 
 template <typename Tree, typename ExecutionSpace, typename Predicates,
           typename Callback, typename Values, typename Offset>
-std::enable_if_t<Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>>
-DistributedTreeImpl::queryDispatch(NearestPredicateTag, Tree const &tree,
-                                   ExecutionSpace const &space,
-                                   Predicates const &predicates,
-                                   Callback const &callback, Values &values,
-                                   Offset &offset)
+  requires(Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>)
+void DistributedTreeImpl::queryDispatch(NearestPredicateTag, Tree const &tree,
+                                        ExecutionSpace const &space,
+                                        Predicates const &predicates,
+                                        Callback const &callback,
+                                        Values &values, Offset &offset)
 {
   if (tree.empty())
   {

src/distributed/detail/ArborX_DistributedTreeSpatial.hpp

@@ -26,12 +26,12 @@ namespace ArborX::Details
 
 template <typename Tree, typename ExecutionSpace, typename Predicates,
           typename Values, typename Offset, typename Callback>
-std::enable_if_t<Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>>
-DistributedTreeImpl::queryDispatch(SpatialPredicateTag, Tree const &tree,
-                                   ExecutionSpace const &space,
-                                   Predicates const &predicates,
-                                   Callback const &callback, Values &values,
-                                   Offset &offset)
+  requires(Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>)
+void DistributedTreeImpl::queryDispatch(SpatialPredicateTag, Tree const &tree,
+                                        ExecutionSpace const &space,
+                                        Predicates const &predicates,
+                                        Callback const &callback,
+                                        Values &values, Offset &offset)
 {
   Kokkos::Profiling::ScopedRegion guard(
       "ArborX::DistributedTree::query::spatial");
@@ -96,11 +96,11 @@ void DistributedTreeImpl::queryDispatch(SpatialPredicateTag, Tree const &tree,
 
 template <typename Tree, typename ExecutionSpace, typename Predicates,
           typename Values, typename Offset>
-std::enable_if_t<Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>>
-DistributedTreeImpl::queryDispatch(SpatialPredicateTag, Tree const &tree,
-                                   ExecutionSpace const &space,
-                                   Predicates const &predicates, Values &values,
-                                   Offset &offset)
+  requires(Kokkos::is_view_v<Values> && Kokkos::is_view_v<Offset>)
+void DistributedTreeImpl::queryDispatch(SpatialPredicateTag, Tree const &tree,
+                                        ExecutionSpace const &space,
+                                        Predicates const &predicates,
+                                        Values &values, Offset &offset)
 {
   queryDispatch(SpatialPredicateTag{}, tree, space, predicates,
                 DefaultCallback{}, values, offset);

src/geometry/algorithms/ArborX_TranslateAndScale.hpp

@@ -20,9 +20,8 @@ namespace ArborX::Details
 {
 // transformation that maps the unit cube into a new axis-aligned box
 // NOTE safe to perform in-place
-template <typename Point, typename Box,
-          std::enable_if_t<GeometryTraits::is_point_v<Point> &&
-                           GeometryTraits::is_box_v<Box>> * = nullptr>
+template <typename Point, typename Box>
+  requires(GeometryTraits::is_point_v<Point> && GeometryTraits::is_box_v<Box>)
 KOKKOS_FUNCTION void translateAndScale(Point const &in, Point &out,
                                        Box const &ref)
 {

src/spatial/ArborX_BruteForce.hpp

@@ -68,9 +68,10 @@ class BruteForce
 
   template <typename ExecutionSpace, typename UserPredicates,
             typename CallbackOrView, typename View, typename... Args>
-  std::enable_if_t<Kokkos::is_view_v<std::decay_t<View>>>
-  query(ExecutionSpace const &space, UserPredicates const &user_predicates,
-        CallbackOrView &&callback_or_view, View &&view, Args &&...args) const
+    requires(Kokkos::is_view_v<std::decay_t<View>>)
+  void query(ExecutionSpace const &space, UserPredicates const &user_predicates,
+             CallbackOrView &&callback_or_view, View &&view,
+             Args &&...args) const
   {
     Kokkos::Profiling::ScopedRegion guard("ArborX::BruteForce::query_crs");
 

src/spatial/ArborX_LinearBVH.hpp

@@ -89,9 +89,10 @@ class BoundingVolumeHierarchy
 
   template <typename ExecutionSpace, typename UserPredicates,
             typename CallbackOrView, typename View, typename... Args>
-  std::enable_if_t<Kokkos::is_view_v<std::decay_t<View>>>
-  query(ExecutionSpace const &space, UserPredicates const &user_predicates,
-        CallbackOrView &&callback_or_view, View &&view, Args &&...args) const
+    requires(Kokkos::is_view_v<std::decay_t<View>>)
+  void query(ExecutionSpace const &space, UserPredicates const &user_predicates,
+             CallbackOrView &&callback_or_view, View &&view,
+             Args &&...args) const
   {
     Kokkos::Profiling::ScopedRegion guard("ArborX::BVH::query_crs");
 

src/spatial/detail/ArborX_AccessTraits.hpp

@@ -32,8 +32,8 @@ using AccessTraitsNotSpecializedArchetypeAlias =
     typename Traits::not_specialized;
 
 template <typename View>
-struct AccessTraits<
-    View, std::enable_if_t<Kokkos::is_view<View>{} && View::rank() == 1>>
+  requires(Kokkos::is_view_v<View> && View::rank() == 1)
+struct AccessTraits<View>
 {
   // Returns a const reference
   KOKKOS_FUNCTION static typename View::const_value_type &get(View const &v,
@@ -49,8 +49,8 @@ struct AccessTraits<
 };
 
 template <typename View>
-struct AccessTraits<
-    View, std::enable_if_t<Kokkos::is_view<View>{} && View::rank() == 2>>
+  requires(Kokkos::is_view_v<View> && View::rank() == 2)
+struct AccessTraits<View>
 {
   template <std::size_t... Is>
   KOKKOS_FUNCTION static auto getPoint(std::index_sequence<Is...>,

src/spatial/detail/ArborX_CrsGraphWrapperImpl.hpp

@@ -328,11 +328,13 @@ struct Iota
 
 template <typename Tag, typename ExecutionSpace, typename Predicates,
           typename OffsetView, typename OutView>
-std::enable_if_t<std::is_same_v<Tag, SpatialPredicateTag> ||
-                 std::is_same_v<Tag, OrderedSpatialPredicateTag>>
-allocateAndInitializeStorage(Tag, ExecutionSpace const &space,
-                             Predicates const &predicates, OffsetView &offset,
-                             OutView &out, int buffer_size)
+  requires(std::is_same_v<Tag, SpatialPredicateTag> ||
+           std::is_same_v<Tag, OrderedSpatialPredicateTag>)
+void allocateAndInitializeStorage(Tag, ExecutionSpace const &space,
+                                  Predicates const &predicates,
+                                  OffsetView &offset, OutView &out,
+                                  int buffer_size)
+
 {
   auto const n_queries = predicates.size();
   KokkosExt::reallocWithoutInitializing(space, offset, n_queries + 1);
@@ -353,10 +355,11 @@ allocateAndInitializeStorage(Tag, ExecutionSpace const &space,
 
 template <typename Tag, typename ExecutionSpace, typename Predicates,
           typename OffsetView, typename OutView>
-std::enable_if_t<std::is_same_v<Tag, NearestPredicateTag>>
-allocateAndInitializeStorage(Tag, ExecutionSpace const &space,
-                             Predicates const &predicates, OffsetView &offset,
-                             OutView &out, int /*buffer_size*/)
+  requires(std::is_same_v<Tag, NearestPredicateTag>)
+void allocateAndInitializeStorage(Tag, ExecutionSpace const &space,
+                                  Predicates const &predicates,
+                                  OffsetView &offset, OutView &out,
+                                  int /*buffer_size*/)
 {
   auto const n_queries = predicates.size();
   KokkosExt::reallocWithoutInitializing(space, offset, n_queries + 1);
@@ -377,13 +380,13 @@ allocateAndInitializeStorage(Tag, ExecutionSpace const &space,
 template <typename Tag, typename Tree, typename ExecutionSpace,
           typename Predicates, typename OutputView, typename OffsetView,
           typename Callback>
-std::enable_if_t<!is_tagged_post_callback<Callback>::value &&
-                 Kokkos::is_view_v<OutputView> && Kokkos::is_view_v<OffsetView>>
-queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
-              Predicates const &predicates, Callback const &callback,
-              OutputView &out, OffsetView &offset,
-              Experimental::TraversalPolicy const &policy =
-                  Experimental::TraversalPolicy())
+  requires(!is_tagged_post_callback<Callback>::value &&
+           Kokkos::is_view_v<OutputView> && Kokkos::is_view_v<OffsetView>)
+void queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
+                   Predicates const &predicates, Callback const &callback,
+                   OutputView &out, OffsetView &offset,
+                   Experimental::TraversalPolicy const &policy =
+                       Experimental::TraversalPolicy())
 {
   check_valid_callback<typename Tree::value_type>(callback, predicates, out);
 
@@ -447,11 +450,12 @@ queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
 
 template <typename Tag, typename Tree, typename ExecutionSpace,
           typename Predicates, typename Indices, typename Offset>
-inline std::enable_if_t<Kokkos::is_view_v<Indices> && Kokkos::is_view_v<Offset>>
-queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
-              Predicates const &predicates, Indices &indices, Offset &offset,
-              Experimental::TraversalPolicy const &policy =
-                  Experimental::TraversalPolicy())
+  requires(Kokkos::is_view_v<Indices> && Kokkos::is_view_v<Offset>)
+inline void queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
+                          Predicates const &predicates, Indices &indices,
+                          Offset &offset,
+                          Experimental::TraversalPolicy const &policy =
+                              Experimental::TraversalPolicy())
 {
   queryDispatch(Tag{}, tree, space, predicates, DefaultCallback{}, indices,
                 offset, policy);
@@ -460,12 +464,13 @@ queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
 template <typename Tag, typename Tree, typename ExecutionSpace,
           typename Predicates, typename OutputView, typename OffsetView,
           typename Callback>
-inline std::enable_if_t<is_tagged_post_callback<Callback>::value>
-queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
-              Predicates const &predicates, Callback const &callback,
-              OutputView &out, OffsetView &offset,
-              Experimental::TraversalPolicy const &policy =
-                  Experimental::TraversalPolicy())
+  requires(is_tagged_post_callback<Callback>::value)
+inline void queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
+                          Predicates const &predicates,
+                          Callback const &callback, OutputView &out,
+                          OffsetView &offset,
+                          Experimental::TraversalPolicy const &policy =
+                              Experimental::TraversalPolicy())
 {
   using MemorySpace = typename Tree::memory_space;
 
@@ -478,9 +483,9 @@ queryDispatch(Tag, Tree const &tree, ExecutionSpace const &space,
 
 template <typename Value, typename Callback, typename Predicates,
           typename OutputView>
-std::enable_if_t<!Kokkos::is_view_v<Callback> &&
-                 !is_tagged_post_callback<Callback>::value>
-check_valid_callback_if_first_argument_is_not_a_view(
+  requires(!Kokkos::is_view_v<Callback> &&
+           !is_tagged_post_callback<Callback>::value)
+void check_valid_callback_if_first_argument_is_not_a_view(
     Callback const &callback, Predicates const &predicates,
     OutputView const &out)
 {
@@ -489,21 +494,21 @@ check_valid_callback_if_first_argument_is_not_a_view(
 
 template <typename Value, typename Callback, typename Predicates,
           typename OutputView>
-std::enable_if_t<!Kokkos::is_view_v<Callback> &&
-                 is_tagged_post_callback<Callback>::value>
-check_valid_callback_if_first_argument_is_not_a_view(Callback const &,
-                                                     Predicates const &,
-                                                     OutputView const &)
+  requires(!Kokkos::is_view_v<Callback> &&
+           is_tagged_post_callback<Callback>::value)
+void check_valid_callback_if_first_argument_is_not_a_view(Callback const &,
+                                                          Predicates const &,
+                                                          OutputView const &)
 {
   // TODO
 }
 
 template <typename Value, typename View, typename Predicates,
           typename OutputView>
-std::enable_if_t<Kokkos::is_view_v<View>>
-check_valid_callback_if_first_argument_is_not_a_view(View const &,
-                                                     Predicates const &,
-                                                     OutputView const &)
+  requires(Kokkos::is_view_v<View>)
+void check_valid_callback_if_first_argument_is_not_a_view(View const &,
+                                                          Predicates const &,
+                                                          OutputView const &)
 {
   // do nothing
 }

src/spatial/detail/ArborX_IndexableGetter.hpp

@@ -33,9 +33,8 @@ struct DefaultIndexableGetter
     return geometry;
   }
 
-  template <typename Geometry,
-            typename Enable = std::enable_if_t<
-                !Details::is_pair_value_index_v<std::decay_t<Geometry>>>>
+  template <typename Geometry>
+    requires(!Details::is_pair_value_index_v<std::decay_t<Geometry>>)
   KOKKOS_FUNCTION auto operator()(Geometry &&geometry) const
   {
     return geometry;

src/spatial/detail/ArborX_MortonCode.hpp

@@ -283,8 +283,8 @@ KOKKOS_INLINE_FUNCTION unsigned long long expandBitsBy<9>(unsigned long long x)
   return x;
 }
 
-template <typename Point,
-          typename Enable = std::enable_if_t<GeometryTraits::is_point_v<Point>>>
+template <typename Point>
+  requires(GeometryTraits::is_point_v<Point>)
 KOKKOS_INLINE_FUNCTION unsigned int morton32(Point const &p)
 {
   constexpr int DIM = GeometryTraits::dimension_v<Point>;
@@ -303,9 +303,9 @@ KOKKOS_INLINE_FUNCTION unsigned int morton32(Point const &p)
   return r;
 }
 
-template <typename Point,
-          std::enable_if_t<GeometryTraits::is_point_v<Point> &&
-                           GeometryTraits::dimension_v<Point> != 2> * = nullptr>
+template <typename Point>
+  requires(GeometryTraits::is_point_v<Point> &&
+           GeometryTraits::dimension_v<Point> != 2)
 KOKKOS_INLINE_FUNCTION unsigned long long morton64(Point const &p)
 {
   constexpr int DIM = GeometryTraits::dimension_v<Point>;
@@ -326,9 +326,9 @@ KOKKOS_INLINE_FUNCTION unsigned long long morton64(Point const &p)
 
 // Calculate a 62-bit Morton code for a 2D point located within [0, 1]^2.
 // Special case because it needs double.
-template <typename Point,
-          std::enable_if_t<GeometryTraits::is_point_v<Point> &&
-                           GeometryTraits::dimension_v<Point> == 2> * = nullptr>
+template <typename Point>
+  requires(GeometryTraits::is_point_v<Point> &&
+           GeometryTraits::dimension_v<Point> == 2)
 KOKKOS_INLINE_FUNCTION unsigned long long morton64(Point const &p)
 {
   // The interval [0,1] is subdivided into 2,147,483,648 bins (in each