Function MakeUnaryRoundFunction

cpp/src/arrow/compute/kernels/scalar_round.cc:1256–1274

// non-null output.
template <template <typename, RoundMode, typename...> class Op, typename OptionsType>
std::shared_ptr<ScalarFunction> MakeUnaryRoundFunction(std::string name,
                                                       FunctionDoc doc) {
  static const OptionsType kDefaultOptions = OptionsType::Defaults();
  auto func = std::make_shared<RoundFunction>(name, Arity::Unary(), std::move(doc),
                                              &kDefaultOptions);
  RoundKernelGenerator<Op, RoundKernel, OptionsType> kernel_generator;
  for (const auto& tys : {NumericTypes(), {decimal128(1, 0), decimal256(1, 0)}}) {
    for (const auto& ty : tys) {
      ArrayKernelExec exec = nullptr;
      KernelInit init;
      DCHECK_OK(VisitTypeInline(*ty, &kernel_generator, &exec, &init));
      DCHECK_OK(func->AddKernel(
          {InputType(ty->id())},
          is_decimal(ty->id()) ? OutputType(FirstType) : OutputType(ty), exec, init));
    }
  }
  AddNullExec(func.get());
  return func;
}

template <template <typename, RoundMode, typename...> class Op, typename OptionsType>
std::shared_ptr<ScalarFunction> MakeBinaryRoundFunction(const std::string& name,