Add isomorphisms.

An isomorphism is a pair of functions between a source and destination
type. Ideally, they should be inverses, but java has no way to check
that by itself.

1 files changed, 60 insertions, 0 deletions

diff --git a/BJC-Utils2/src/main/java/bjc/utils/funcutils/Isomorphism.java b/BJC-Utils2/src/main/java/bjc/utils/funcutils/Isomorphism.java
new file mode 100644
index 0000000..2d3655e
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/funcutils/Isomorphism.java
@@ -0,0 +1,60 @@
+package bjc.utils.funcutils;
+
+import java.util.function.Function;
+
+/**
+ * A pair of functions to transform between a pair of types.
+ * 
+ * @author bjculkin
+ * 
+ * @param <S>
+ *                The source type of the isomorphism.
+ * 
+ * @param <D>
+ *                The destination type of isomorphism.
+ *
+ */
+public class Isomorphism<S, D> {
+	private Function<S, D>	toFunc;
+	private Function<D, S>	fromFunc;
+
+	/**
+	 * Create a new isomorphism.
+	 * 
+	 * @param to
+	 *                The 'forward' function, from the source to the
+	 *                definition.
+	 * 
+	 * @param from
+	 *                The 'backward' function, from the definition to the
+	 *                source.
+	 */
+	public Isomorphism(Function<S, D> to, Function<D, S> from) {
+		toFunc = to;
+		fromFunc = from;
+	}
+
+	/**
+	 * Apply the isomorphism forward.
+	 * 
+	 * @param val
+	 *                The source value.
+	 * 
+	 * @return The destination value.
+	 */
+	public D to(S val) {
+		return toFunc.apply(val);
+	}
+
+	/**
+	 * Apply the isomorphism backward.
+	 * 
+	 * @param val
+	 *                The destination value.
+	 * 
+	 * @return The source value.
+	 */
+	public S from(D val) {
+		return fromFunc.apply(val);
+	}
+}