From 1e3e91f815e26d77569cea639a2cd26be21550ac Mon Sep 17 00:00:00 2001
From: "Benjamin J. Culkin" <bjculkin@mix.wvu.edu>
Date: Thu, 11 Apr 2019 18:59:33 -0300
Subject: ChainIterators

---
 .../java/bjc/utils/funcutils/IteratorUtils.java    | 34 ++++++++++++++++++++++
 1 file changed, 34 insertions(+)

(limited to 'base/src/main/java/bjc/utils/funcutils')

diff --git a/base/src/main/java/bjc/utils/funcutils/IteratorUtils.java b/base/src/main/java/bjc/utils/funcutils/IteratorUtils.java
index c639da6..3cdee26 100644
--- a/base/src/main/java/bjc/utils/funcutils/IteratorUtils.java
+++ b/base/src/main/java/bjc/utils/funcutils/IteratorUtils.java
@@ -10,6 +10,36 @@ import java.util.function.Function;
  *
  */
 public class IteratorUtils {
+	public static class ChainIterator<T1, T2> implements Iterator<T2> {
+		private Iterator<T1> mainItr;
+		private Function<T1, Iterator<T2>> trans;
+
+		private Iterator<T2> curItr;
+
+		public ChainIterator(Iterator<T1> mainItr, Function<T1, Iterator<T2>> trans) {
+			this.mainItr = mainItr;
+			this.trans   = trans;
+		}
+
+		@Override
+		public boolean hasNext() {
+			if (curItr != null) {
+				if (curItr.hasNext()) return true;
+				else                  return mainItr.hasNext();
+			}
+
+			return mainItr.hasNext();
+		}
+
+		@Override
+		public T2 next() {
+			if (curItr == null || !curItr.hasNext()) {
+				curItr = trans.apply(mainItr.next());
+			}
+
+			return curItr.next();
+		}
+	}
 	/**
 	 * Convert an iterator to an iterable.
 	 * 
@@ -31,4 +61,8 @@ public class IteratorUtils {
 	public static <E> Iterator<E> I(Iterable<E> itr) {
 		return itr.iterator();
 	}
+
+	public static <A, B> Iterator<B> chain(Iterator<A> itrA, Function<A, Iterator<B>> itrB) {
+		return new ChainIterator(itrA, itrB);
+	}
 }
-- 
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