Function RunMain

cpp/examples/arrow/compute_and_write_csv_example.cc:43–82

// in the current directory

arrow::Status RunMain(int argc, char** argv) {
  ARROW_RETURN_NOT_OK(arrow::compute::Initialize());
  // Make Arrays
  arrow::NumericBuilder<arrow::Int64Type> int64_builder;
  arrow::BooleanBuilder boolean_builder;

  // Make place for 8 values in total
  ARROW_RETURN_NOT_OK(int64_builder.Resize(8));
  ARROW_RETURN_NOT_OK(boolean_builder.Resize(8));

  // Bulk append the given values
  std::vector<int64_t> int64_values = {1, 2, 3, 4, 5, 6, 7, 8};
  ARROW_RETURN_NOT_OK(int64_builder.AppendValues(int64_values));
  std::shared_ptr<arrow::Array> array_a;
  ARROW_RETURN_NOT_OK(int64_builder.Finish(&array_a));
  int64_builder.Reset();
  int64_values = {2, 5, 1, 3, 6, 2, 7, 4};
  std::shared_ptr<arrow::Array> array_b;
  ARROW_RETURN_NOT_OK(int64_builder.AppendValues(int64_values));
  ARROW_RETURN_NOT_OK(int64_builder.Finish(&array_b));

  // Cast the arrays to their actual types
  auto int64_array_a = std::static_pointer_cast<arrow::Int64Array>(array_a);
  auto int64_array_b = std::static_pointer_cast<arrow::Int64Array>(array_b);
  // Explicit comparison of values using a loop
  for (int64_t i = 0; i < 8; i++) {
    if ((!int64_array_a->IsNull(i)) && (!int64_array_b->IsNull(i))) {
      bool comparison_result = int64_array_a->Value(i) > int64_array_b->Value(i);
      boolean_builder.UnsafeAppend(comparison_result);
    } else {
      boolean_builder.UnsafeAppendNull();
    }
  }
  std::shared_ptr<arrow::Array> array_a_gt_b_self;
  ARROW_RETURN_NOT_OK(boolean_builder.Finish(&array_a_gt_b_self));
  std::cout << "Array explicitly compared" << std::endl;

  // Explicit comparison of values using a compute function
  ARROW_ASSIGN_OR_RAISE(arrow::Datum compared_datum,
                        arrow::compute::CallFunction("greater", {array_a, array_b}));
  auto array_a_gt_b_compute = compared_datum.make_array();
  std::cout << "Arrays compared using a compute function" << std::endl;