1 files changed, 70 insertions, 0 deletions
diff --git a/src/main/java/bjc/optics/Prism.java b/src/main/java/bjc/optics/Prism.java
new file mode 100644
index 0000000..a04939b
--- /dev/null
+++ b/src/main/java/bjc/optics/Prism.java
@@ -0,0 +1,70 @@
+/* 
+ * 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.optics;
+
+import java.util.function.Function;
+
+import bjc.data.Either;
+import bjc.typeclasses.BiContainer;
+
+/**
+ * A type-invariant prism
+ * 
+ * @author bjcul
+ *
+ * @param <Whole> The type of the whole
+ * @param <Part>  The type of the part
+ */
+public interface Prism<Whole, Part>
+		extends PrismX<Whole, Whole, Part, Part>, BiContainer<Whole, Part, Prism<Whole, Part>> {
+
+	/**
+	 * Create a type-invariant prism from its component parts.
+	 * 
+	 * @param <Whole> The type of the whole
+	 * @param <Part>  The type of the part
+	 * 
+	 * @param f       The 'match' function of the prism
+	 * @param g       The 'build' function of the prism
+	 * 
+	 * @return The prism composed of the given parts.
+	 */
+	static <Whole, Part> Prism<Whole, Part> of(Function<Part, Either<Part, Whole>> f, Function<Whole, Part> g) {
+		return new FunctionalPrism<>(g, f);
+	}
+}
+
+final class FunctionalPrism<Whole, Part> implements Prism<Whole, Part> {
+	private final Function<Whole, Part> g;
+	private final Function<Part, Either<Part, Whole>> f;
+
+	public FunctionalPrism(Function<Whole, Part> g, Function<Part, Either<Part, Whole>> f) {
+		this.g = g;
+		this.f = f;
+	}
+
+	@Override
+	public Part build(Whole whole) {
+		return g.apply(whole);
+	}
+
+	@Override
+	public Either<Part, Whole> match(Part part) {
+		return f.apply(part);
+	}
+}
+\ No newline at end of file