1 files changed, 54 insertions, 0 deletions
diff --git a/src/main/java/bjc/optics/TraversalX.java b/src/main/java/bjc/optics/TraversalX.java
new file mode 100644
index 0000000..54c1a0b
--- /dev/null
+++ b/src/main/java/bjc/optics/TraversalX.java
@@ -0,0 +1,54 @@
+/* 
+ * esodata - data structures of varying use
+ * 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.optics;
+
+import java.util.Collection;
+
+/**
+ * Represents an optic allowing access to the elements of a given item
+ * 
+ * @author bjcul
+ *
+ * @param <C1> The first collection type
+ * @param <C2> The second collection type
+ * @param <E1> The first element type
+ * @param <E2> The second element type
+ */
+public interface TraversalX<C1, C2, E1, E2> extends Optic<C1, C2, E1, E2> {
+	// Note: these should be fixed size collections of the same type, but that would
+	// be awkward to represent
+	/**
+	 * Extract the contents of the collection
+	 * 
+	 * @param whole The collection to get the contents of.
+	 * @return The contents of the given collection.
+	 */
+	Collection<E1> contents(C1 whole);
+
+	/**
+	 * Replace the contents of the given collection
+	 * 
+	 * @param whole The collection to replace the contents of
+	 * @param bits  The new contents of the collection
+	 * 
+	 * @return A collection with the new contents
+	 */
+	C2 fill(C1 whole, Collection<E2> bits);
+	
+	// TODO implement 'of'
+}