void main() {
        StreamF.of(1, 2, 3, 4)
                .apply(Main::up)
                .add(Stream::flatMap, Function.identity())
                .s
                .forEach(System.out::println);

    }

    public static <T> Stream<Stream<T>> up(Stream<T> s) {
        return Stream.of(s);
    }

    record StreamF<T>(Stream<T> s) {
        @SafeVarargs
        static <T> StreamF<T> of(T... t) {
            return new StreamF<>(Stream.of(t));
        }

        public <V> StreamF<V> add(BiFunction<Stream<T>, Function<T, Stream<V>>, Stream<V>> f, Function<T, Stream<V>> c) {
            return new StreamF<>(f.apply(s, c));
        }

        public <V> StreamF<V> apply(Function<? super Stream<T>, ? extends Stream<V>> c) {
            return new StreamF<>(c.apply(s));
        }
    }