private static void test(IntStream inputStream, BlockComparator comparator, PrimitiveIterator.OfInt outputIterator)
{
    BlockBuilder blockBuilder = BIGINT.createBlockBuilder(null, INPUT_SIZE);
    inputStream.forEach(x -> BIGINT.writeLong(blockBuilder, x));

    TypedHeap heap = new TypedHeap(comparator, BIGINT, OUTPUT_SIZE);
    heap.addAll(blockBuilder);

    BlockBuilder resultBlockBuilder = BIGINT.createBlockBuilder(null, OUTPUT_SIZE);
    heap.popAll(resultBlockBuilder);

    Block resultBlock = resultBlockBuilder.build();
    assertEquals(resultBlock.getPositionCount(), OUTPUT_SIZE);
    for (int i = 0; i < OUTPUT_SIZE; i++) {
        assertEquals(BIGINT.getLong(resultBlock, i), outputIterator.nextInt());
    }
}
 

/**
 * Returns an infinite sequential ordered {@code IntStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code IntStream} will be
 * the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return A new sequential {@code IntStream}
 */
public static IntStream iterate(final int seed, final IntUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() {
        int t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public int nextInt() {
            int v = t;
            t = f.applyAsInt(t);
            return v;
        }
    };
    return StreamSupport.intStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code DoubleStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code DoubleStream}
 * will be the provided {@code seed}.  For {@code n > 0}, the element at
 * position {@code n}, will be the result of applying the function {@code f}
 *  to the element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return a new sequential {@code DoubleStream}
 */
public static DoubleStream iterate(final double seed, final DoubleUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfDouble iterator = new PrimitiveIterator.OfDouble() {
        double t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public double nextDouble() {
            double v = t;
            t = f.applyAsDouble(t);
            return v;
        }
    };
    return StreamSupport.doubleStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code LongStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code LongStream} will
 * be the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return a new sequential {@code LongStream}
 */
public static LongStream iterate(final long seed, final LongUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfLong iterator = new PrimitiveIterator.OfLong() {
        long t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public long nextLong() {
            long v = t;
            t = f.applyAsLong(t);
            return v;
        }
    };
    return StreamSupport.longStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code LongStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code LongStream} will
 * be the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return a new sequential {@code LongStream}
 */
public static LongStream iterate(final long seed, final LongUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfLong iterator = new PrimitiveIterator.OfLong() {
        long t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public long nextLong() {
            long v = t;
            t = f.applyAsLong(t);
            return v;
        }
    };
    return StreamSupport.longStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

@Test(dataProvider = "cases")
public void testBitsetStream(String name, IntStream data) {
    BitSet bs = new BitSet();
    long setBits = data.distinct()
                       .peek(i -> bs.set(i))
                       .count();

    assertEquals(bs.cardinality(), setBits);
    assertEquals(bs.cardinality(), bs.stream().reduce(0, (s, i) -> s+1));

    PrimitiveIterator.OfInt it = bs.stream().iterator();
    for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
        assertTrue(it.hasNext());
        assertEquals(it.nextInt(), i);
    }
    assertFalse(it.hasNext());
}
 

public void testDoubleForEachRemainingWithNull() {
    PrimitiveIterator.OfDouble i = new PrimitiveIterator.OfDouble() {
        @Override
        public double nextDouble() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((DoubleConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Double>) null));
}
 

/**
 * Returns an infinite sequential ordered {@code LongStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code LongStream} will
 * be the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to the previous element to produce
 *          a new element
 * @return a new sequential {@code LongStream}
 */
public static LongStream iterate(final long seed, final LongUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfLong iterator = new PrimitiveIterator.OfLong() {
        long t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public long nextLong() {
            long v = t;
            t = f.applyAsLong(t);
            return v;
        }
    };
    return StreamSupport.longStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code DoubleStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code DoubleStream}
 * will be the provided {@code seed}.  For {@code n > 0}, the element at
 * position {@code n}, will be the result of applying the function {@code f}
 *  to the element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to the previous element to produce
 *          a new element
 * @return a new sequential {@code DoubleStream}
 */
public static DoubleStream iterate(final double seed, final DoubleUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfDouble iterator = new PrimitiveIterator.OfDouble() {
        double t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public double nextDouble() {
            double v = t;
            t = f.applyAsDouble(t);
            return v;
        }
    };
    return StreamSupport.doubleStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code IntStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code IntStream} will be
 * the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to the previous element to produce
 *          a new element
 * @return A new sequential {@code IntStream}
 */
public static IntStream iterate(final int seed, final IntUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() {
        int t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public int nextInt() {
            int v = t;
            t = f.applyAsInt(t);
            return v;
        }
    };
    return StreamSupport.intStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

public void testLongForEachRemainingWithNull() {
    PrimitiveIterator.OfLong i = new PrimitiveIterator.OfLong() {
        @Override
        public long nextLong() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((LongConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Long>) null));
}
 

public void testLongForEachRemainingWithNull() {
    PrimitiveIterator.OfLong i = new PrimitiveIterator.OfLong() {
        @Override
        public long nextLong() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((LongConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Long>) null));
}
 

public void testDoubleForEachRemainingWithNull() {
    PrimitiveIterator.OfDouble i = new PrimitiveIterator.OfDouble() {
        @Override
        public double nextDouble() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((DoubleConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Double>) null));
}
 

/**
 * Returns an infinite sequential ordered {@code IntStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code IntStream} will be
 * the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return A new sequential {@code IntStream}
 */
public static IntStream iterate(final int seed, final IntUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() {
        int t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public int nextInt() {
            int v = t;
            t = f.applyAsInt(t);
            return v;
        }
    };
    return StreamSupport.intStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code IntStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code IntStream} will be
 * the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to the previous element to produce
 *          a new element
 * @return A new sequential {@code IntStream}
 */
public static IntStream iterate(final int seed, final IntUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() {
        int t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public int nextInt() {
            int v = t;
            t = f.applyAsInt(t);
            return v;
        }
    };
    return StreamSupport.intStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

@Test(dataProvider = "cases")
public void testBitsetStream(String name, IntStream data) {
    BitSet bs = new BitSet();
    long setBits = data.distinct()
                       .peek(i -> bs.set(i))
                       .count();

    assertEquals(bs.cardinality(), setBits);
    assertEquals(bs.cardinality(), bs.stream().reduce(0, (s, i) -> s+1));

    PrimitiveIterator.OfInt it = bs.stream().iterator();
    for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
        assertTrue(it.hasNext());
        assertEquals(it.nextInt(), i);
    }
    assertFalse(it.hasNext());
}
 

public void testIntForEachRemainingWithNull() {
    PrimitiveIterator.OfInt i = new PrimitiveIterator.OfInt() {
        @Override
        public int nextInt() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((IntConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Integer>) null));
}
 

public void testIntForEachRemainingWithNull() {
    PrimitiveIterator.OfInt i = new PrimitiveIterator.OfInt() {
        @Override
        public int nextInt() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((IntConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Integer>) null));
}
 

public void testLongForEachRemainingWithNull() {
    PrimitiveIterator.OfLong i = new PrimitiveIterator.OfLong() {
        @Override
        public long nextLong() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((LongConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Long>) null));
}
 

public void testDoubleForEachRemainingWithNull() {
    PrimitiveIterator.OfDouble i = new PrimitiveIterator.OfDouble() {
        @Override
        public double nextDouble() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((DoubleConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Double>) null));
}
 

@Test(dataProvider = "cases")
public void testBitsetStream(String name, IntStream data) {
    BitSet bs = new BitSet();
    long setBits = data.distinct()
                       .peek(i -> bs.set(i))
                       .count();

    assertEquals(bs.cardinality(), setBits);
    assertEquals(bs.cardinality(), bs.stream().reduce(0, (s, i) -> s+1));

    PrimitiveIterator.OfInt it = bs.stream().iterator();
    for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
        assertTrue(it.hasNext());
        assertEquals(it.nextInt(), i);
    }
    assertFalse(it.hasNext());
}
 

public void testDoubleForEachRemainingWithNull() {
    PrimitiveIterator.OfDouble i = new PrimitiveIterator.OfDouble() {
        @Override
        public double nextDouble() {
            return 0;
        }

        @Override
        public boolean hasNext() {
            return false;
        }
    };

    executeAndCatch(() -> i.forEachRemaining((DoubleConsumer) null));
    executeAndCatch(() -> i.forEachRemaining((Consumer<Double>) null));
}
 

/**
 * Returns an infinite sequential ordered {@code IntStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code IntStream} will be
 * the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return A new sequential {@code IntStream}
 */
public static IntStream iterate(final int seed, final IntUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() {
        int t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public int nextInt() {
            int v = t;
            t = f.applyAsInt(t);
            return v;
        }
    };
    return StreamSupport.intStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code LongStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code LongStream} will
 * be the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return a new sequential {@code LongStream}
 */
public static LongStream iterate(final long seed, final LongUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfLong iterator = new PrimitiveIterator.OfLong() {
        long t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public long nextLong() {
            long v = t;
            t = f.applyAsLong(t);
            return v;
        }
    };
    return StreamSupport.longStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code LongStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code LongStream} will
 * be the provided {@code seed}.  For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return a new sequential {@code LongStream}
 */
public static LongStream iterate(final long seed, final LongUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfLong iterator = new PrimitiveIterator.OfLong() {
        long t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public long nextLong() {
            long v = t;
            t = f.applyAsLong(t);
            return v;
        }
    };
    return StreamSupport.longStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns an infinite sequential ordered {@code DoubleStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code DoubleStream}
 * will be the provided {@code seed}.  For {@code n > 0}, the element at
 * position {@code n}, will be the result of applying the function {@code f}
 *  to the element at position {@code n - 1}.
 *
 * @param seed the initial element
 * @param f a function to be applied to to the previous element to produce
 *          a new element
 * @return a new sequential {@code DoubleStream}
 */
public static DoubleStream iterate(final double seed, final DoubleUnaryOperator f) {
    Objects.requireNonNull(f);
    final PrimitiveIterator.OfDouble iterator = new PrimitiveIterator.OfDouble() {
        double t = seed;

        @Override
        public boolean hasNext() {
            return true;
        }

        @Override
        public double nextDouble() {
            double v = t;
            t = f.applyAsDouble(t);
            return v;
        }
    };
    return StreamSupport.doubleStream(Spliterators.spliteratorUnknownSize(
            iterator,
            Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
 

/**
 * Returns a stream of {@code int} zero-extending the {@code char} values
 * from this sequence.  Any char which maps to a <a
 * href="{@docRoot}/java/lang/Character.html#unicode">surrogate code
 * point</a> is passed through uninterpreted.
 *
 * <p>If the sequence is mutated while the stream is being read, the
 * result is undefined.
 *
 * @return an IntStream of char values from this sequence
 * @since 1.8
 */
public default IntStream chars() {
    class CharIterator implements PrimitiveIterator.OfInt {
        int cur = 0;

        public boolean hasNext() {
            return cur < length();
        }

        public int nextInt() {
            if (hasNext()) {
                return charAt(cur++);
            } else {
                throw new NoSuchElementException();
            }
        }

        @Override
        public void forEachRemaining(IntConsumer block) {
            for (; cur < length(); cur++) {
                block.accept(charAt(cur));
            }
        }
    }

    return StreamSupport.intStream(() ->
            Spliterators.spliterator(
                    new CharIterator(),
                    length(),
                    Spliterator.ORDERED),
            Spliterator.SUBSIZED | Spliterator.SIZED | Spliterator.ORDERED,
            false);
}
 

/**
 * Returns a stream of {@code int} zero-extending the {@code char} values
 * from this sequence.  Any char which maps to a <a
 * href="{@docRoot}/java/lang/Character.html#unicode">surrogate code
 * point</a> is passed through uninterpreted.
 *
 * <p>If the sequence is mutated while the stream is being read, the
 * result is undefined.
 *
 * @return an IntStream of char values from this sequence
 * @since 1.8
 */
public default IntStream chars() {
    class CharIterator implements PrimitiveIterator.OfInt {
        int cur = 0;

        public boolean hasNext() {
            return cur < length();
        }

        public int nextInt() {
            if (hasNext()) {
                return charAt(cur++);
            } else {
                throw new NoSuchElementException();
            }
        }

        @Override
        public void forEachRemaining(IntConsumer block) {
            for (; cur < length(); cur++) {
                block.accept(charAt(cur));
            }
        }
    }

    return StreamSupport.intStream(() ->
            Spliterators.spliterator(
                    new CharIterator(),
                    length(),
                    Spliterator.ORDERED),
            Spliterator.SUBSIZED | Spliterator.SIZED | Spliterator.ORDERED,
            false);
}
 

/**
 * Returns a stream of {@code int} zero-extending the {@code char} values
 * from this sequence.  Any char which maps to a <a
 * href="{@docRoot}/java/lang/Character.html#unicode">surrogate code
 * point</a> is passed through uninterpreted.
 *
 * <p>If the sequence is mutated while the stream is being read, the
 * result is undefined.
 *
 * @return an IntStream of char values from this sequence
 * @since 1.8
 */
public default IntStream chars() {
    class CharIterator implements PrimitiveIterator.OfInt {
        int cur = 0;

        public boolean hasNext() {
            return cur < length();
        }

        public int nextInt() {
            if (hasNext()) {
                return charAt(cur++);
            } else {
                throw new NoSuchElementException();
            }
        }

        @Override
        public void forEachRemaining(IntConsumer block) {
            for (; cur < length(); cur++) {
                block.accept(charAt(cur));
            }
        }
    }

    return StreamSupport.intStream(() ->
            Spliterators.spliterator(
                    new CharIterator(),
                    length(),
                    Spliterator.ORDERED),
            Spliterator.SUBSIZED | Spliterator.SIZED | Spliterator.ORDERED,
            false);
}
 

private Node.OfInt degenerateTree(PrimitiveIterator.OfInt it) {
    if (!it.hasNext()) {
        return Nodes.node(new int[0]);
    }

    int i = it.nextInt();
    if (it.hasNext()) {
        return new Nodes.ConcNode.OfInt(Nodes.node(new int[] {i}), degenerateTree(it));
    }
    else {
        return Nodes.node(new int[] {i});
    }
}