[GitHub] [arrow] jorisvandenbossche commented on a change in pull request #10349: ARROW-12744: [C++][Compute] Add rounding kernel

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jorisvandenbossche commented on a change in pull request #10349:
URL: https://github.com/apache/arrow/pull/10349#discussion_r634139326



##########
File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
##########
@@ -355,6 +355,32 @@ struct PowerChecked {
   }
 };
 
+struct Round {
+  template <typename T, typename Arg>
+  static constexpr enable_if_floating_point<T> Call(KernelContext*, Arg arg, Status*) {
+    return std::round(arg);
+  }
+
+  template <typename T, typename Arg>
+  static constexpr enable_if_integer<T> Call(KernelContext*, Arg arg, Status*) {
+    return arg;
+  }
+};
+
+struct RoundChecked {
+  template <typename T, typename Arg>
+  static constexpr enable_if_integer<T> Call(KernelContext*, Arg arg, Status*) {
+    static_assert(std::is_same<T, Arg>::value, "");
+    return arg;
+  }
+
+  template <typename T, typename Arg>
+  static constexpr enable_if_floating_point<T> Call(KernelContext*, Arg arg, Status*) {
+    static_assert(std::is_same<T, Arg>::value, "");

Review comment:
       But should a `round` kernel ever change the type? IMO when rounding floats, the result can still be floats, regardless of the number of decimals to round




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