Function MakeMappedGenerator

cpp/src/arrow/util/async_generator.h:271–276

          typename Mapped = detail::result_of_t<MapFn(const T&)>,
          typename V = typename EnsureFuture<Mapped>::type::ValueType>
AsyncGenerator<V> MakeMappedGenerator(AsyncGenerator<T> source_generator, MapFn map) {
  auto map_callback = [map = std::move(map)](const T& val) mutable -> Future<V> {
    return ToFuture(map(val));
  };
  return MappingGenerator<T, V>(std::move(source_generator), std::move(map_callback));
}

/// \brief Create a generator that will apply the map function to
/// each element of source.  The map function is not called on the end