Allow using counting_iterator with datapar policies

Signed-off-by: Hartmut Kaiser <hartmut.kaiser@gmail.com>

Author: hkaiser

libs/core/algorithms/include/hpx/parallel/algorithms/count.hpp

@@ -272,9 +272,9 @@ namespace hpx::parallel {
             count_iteration& operator=(count_iteration&&) = default;
 
             template <typename Iter>
-            HPX_HOST_DEVICE HPX_FORCEINLINE constexpr
-                typename std::iterator_traits<Iter>::difference_type
-                operator()(Iter part_begin, std::size_t part_size)
+            HPX_HOST_DEVICE HPX_FORCEINLINE constexpr std::iterator_traits<
+                Iter>::difference_type
+            operator()(Iter part_begin, std::size_t part_size)
             {
                 typename std::iterator_traits<Iter>::difference_type ret = 0;
                 util::loop_n<execution_policy_type>(part_begin, part_size,
@@ -283,8 +283,8 @@ namespace hpx::parallel {
             }
 
             template <typename Iter>
-            HPX_HOST_DEVICE HPX_FORCEINLINE constexpr void operator()(Iter curr,
-                typename std::iterator_traits<Iter>::difference_type& ret)
+            HPX_HOST_DEVICE HPX_FORCEINLINE constexpr void operator()(
+                Iter curr, std::iterator_traits<Iter>::difference_type& ret)
             {
                 ret += traits::count_bits(
                     HPX_INVOKE(op_, HPX_INVOKE(proj_, *curr)));
@@ -295,7 +295,7 @@ namespace hpx::parallel {
         HPX_CXX_CORE_EXPORT template <typename Value>
         struct count : public algorithm<count<Value>, Value>
         {
-            typedef Value difference_type;
+            using difference_type = Value;
 
             constexpr count() noexcept
               : algorithm<count, Value>("count")
@@ -429,7 +429,7 @@ namespace hpx {
     {
     private:
         template <typename ExPolicy, typename FwdIter,
-            typename T = typename std::iterator_traits<FwdIter>::value_type>
+            typename T = std::iterator_traits<FwdIter>::value_type>
         // clang-format off
             requires (
                 hpx::is_execution_policy_v<ExPolicy> &&
@@ -443,28 +443,28 @@ namespace hpx {
                 "Required at least forward iterator.");
 
             using difference_type =
-                typename std::iterator_traits<FwdIter>::difference_type;
+                std::iterator_traits<FwdIter>::difference_type;
 
             return hpx::parallel::detail::count<difference_type>().call(
                 HPX_FORWARD(ExPolicy, policy), first, last, value,
                 hpx::identity_v);
         }
 
         template <typename InIter,
-            typename T = typename std::iterator_traits<InIter>::value_type>
+            typename T = std::iterator_traits<InIter>::value_type>
         // clang-format off
             requires (
                 hpx::traits::is_iterator_v<InIter>
             )
         // clang-format on
-        friend typename std::iterator_traits<InIter>::difference_type
+        friend std::iterator_traits<InIter>::difference_type
         tag_fallback_invoke(count_t, InIter first, InIter last, T const& value)
         {
             static_assert(std::input_iterator<InIter>,
                 "Required at least input iterator.");
 
             using difference_type =
-                typename std::iterator_traits<InIter>::difference_type;
+                std::iterator_traits<InIter>::difference_type;
 
             return hpx::parallel::detail::count<difference_type>().call(
                 hpx::execution::seq, first, last, value, hpx::identity_v);
@@ -494,7 +494,7 @@ namespace hpx {
                 "Required at least forward iterator.");
 
             using difference_type =
-                typename std::iterator_traits<FwdIter>::difference_type;
+                std::iterator_traits<FwdIter>::difference_type;
 
             return hpx::parallel::detail::count_if<difference_type>().call(
                 HPX_FORWARD(ExPolicy, policy), first, last, HPX_MOVE(f),
@@ -510,14 +510,14 @@ namespace hpx {
                 >
             )
         // clang-format on
-        friend typename std::iterator_traits<InIter>::difference_type
+        friend std::iterator_traits<InIter>::difference_type
         tag_fallback_invoke(count_if_t, InIter first, InIter last, F f)
         {
             static_assert(std::input_iterator<InIter>,
                 "Required at least input iterator.");
 
             using difference_type =
-                typename std::iterator_traits<InIter>::difference_type;
+                std::iterator_traits<InIter>::difference_type;
 
             return hpx::parallel::detail::count_if<difference_type>().call(
                 hpx::execution::seq, first, last, HPX_MOVE(f), hpx::identity_v);