Implement NestList

NestList is a recursive list structure, inspired by the way lists work
in Rakudo (formerly Perl 6).

1 files changed, 103 insertions, 0 deletions

diff --git a/src/main/java/bjc/esodata/FlatNestIterator.java b/src/main/java/bjc/esodata/FlatNestIterator.java
new file mode 100644
index 0000000..42981f5
--- /dev/null
+++ b/src/main/java/bjc/esodata/FlatNestIterator.java
@@ -0,0 +1,103 @@
+package bjc.esodata;
+
+import java.util.*;
+
+import bjc.data.*;
+
+final class FlatNestIterator<Element> implements ListIterator<Element>
+{
+	private Deque<ListIterator<Either<Element, NestList<Element>>>> iterators;
+	
+	public FlatNestIterator(ListIterator<Either<Element, NestList<Element>>> iterator)
+	{
+		this.iterators = new ArrayDeque<>();
+		this.iterators.add(iterator);
+	}
+
+	@Override
+	public boolean hasNext() {
+		boolean result = false;
+		do {
+			result = iterators.peek().hasNext();
+			
+			if (result == false) iterators.pop();
+		} while (result == false && iterators.isEmpty() == false);
+		
+		return result;
+	}
+
+	@Override
+	public Element next() {
+		Holder<Element> element = Holder.of(null);
+		do {
+			element = iterators.peek().next().extract((ele) -> {
+				return Holder.of(ele);
+			}, (lst) -> {
+				// Ignore empty sublists.
+				if (lst.size() != 0) iterators.push(lst.listIterator());
+				
+				return null;
+			});
+		} while (element == null && hasNext());
+
+		if (element == null) throw new NoSuchElementException();
+		
+		return element.getValue();
+	}
+
+	@Override
+	public boolean hasPrevious() {
+		boolean result = false;
+		do {
+			result = iterators.peek().hasPrevious();
+			
+			if (result == false) iterators.pop();
+		} while (result == false && iterators.isEmpty() == false);
+		
+		return result;
+	}
+
+	@Override
+	public Element previous() {
+		Holder<Element> element = Holder.of(null);
+		do {
+			element = iterators.peek().previous().extract((ele) -> {
+				return Holder.of(ele);
+			}, (lst) -> {
+				// Ignore empty sublists.
+				if (lst.size() != 0) iterators.push(lst.listIterator());
+				
+				return null;
+			});
+		} while (element == null && hasPrevious());
+
+		if (element == null) throw new NoSuchElementException();
+		
+		return element.getValue();
+	}
+
+	@Override
+	public int nextIndex() {
+		return iterators.peek().nextIndex();
+	}
+
+	@Override
+	public int previousIndex() {
+		return iterators.peek().previousIndex();
+	}
+
+	@Override
+	public void remove() {
+		iterators.peek().remove();
+	}
+
+	@Override
+	public void set(Element e) {
+		iterators.peek().set(Either.left(e));
+	}
+
+	@Override
+	public void add(Element e) {
+		iterators.peek().add(Either.left(e));
+	}
+}
\ No newline at end of file