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diff --git a/src/main/java/bjc/data/CollectionUtils.java b/src/main/java/bjc/data/CollectionUtils.java
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+++ b/src/main/java/bjc/data/CollectionUtils.java
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+/* 
+ * esodata - data structures of varying utility
+ * Copyright 2022, Ben Culkin
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *   
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package bjc.data;
+
+import java.util.*;
+import java.util.function.Function;
+
+/**
+ * Various utilities for dealing w/ collections
+ * @author bjcul
+ *
+ */
+public class CollectionUtils {
+	/**
+	 * Create a function that converts a collection into a map.
+	 * 
+	 * @param <Val>   The type of the values in the map
+	 * @param <Idx>   The type of the keys in the map
+	 * @param <Ent>   The type of the values in the collection
+	 * 
+	 * @param keyFunc The function that determines keys
+	 * @param valFunc The function that determines values
+	 * 
+	 * @return A function which uses the provided function to create a map from a
+	 *         collection.
+	 */
+	public static <Val, Idx, Ent> Function<Collection<Ent>, Map<Idx, Val>> indexBy(Function<Ent, Idx> keyFunc,
+			Function<Ent, Val> valFunc) {
+		return (coll) -> {
+			Map<Idx, Val> mep = new HashMap<>();
+
+			for (Ent ent : coll) {
+				mep.put(keyFunc.apply(ent), valFunc.apply(ent));
+			}
+
+			return mep;
+		};
+	}
+}