Function MakeFirstNGeneric

cpp/src/arrow/util/iterator_test.cc:251–260

template <typename T>
Transformer<T, T> MakeFirstNGeneric(int n) {
  int remaining = n;
  return [remaining](T next) mutable -> Result<TransformFlow<T>> {
    if (remaining > 0) {
      remaining--;
      return TransformYield(next);
    }
    return TransformFinish();
  };
}

TEST(TestIteratorTransform, Truncating) {
  auto original = VectorIt({1, 2, 3});