From 44be6e6cd7671dd243056107ffa6201504f7fbce Mon Sep 17 00:00:00 2001
From: Ben Culkin <scorpress@gmail.com>
Date: Sun, 25 Jun 2023 15:50:38 -0400
Subject: Update a number of things

---
 src/main/java/bjc/optics/Prisms.java | 56 ++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 src/main/java/bjc/optics/Prisms.java

(limited to 'src/main/java/bjc/optics/Prisms.java')

diff --git a/src/main/java/bjc/optics/Prisms.java b/src/main/java/bjc/optics/Prisms.java
new file mode 100644
index 0000000..ae4a4ee
--- /dev/null
+++ b/src/main/java/bjc/optics/Prisms.java
@@ -0,0 +1,56 @@
+/* 
+ * 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.Optional;
+
+import bjc.data.Either;
+
+/**
+ * Various utilities for working with prisms
+ * 
+ * @author bjcul
+ *
+ */
+public class Prisms {
+	/**
+	 * Create a prism that reflects on the value in an optional
+	 * 
+	 * @param <L> The type contained in the optional
+	 * @param <R> An auxiliary type
+	 * 
+	 *            TODO: better notes for what R is for
+	 * 
+	 * @return A prism that reflects on an optional
+	 */
+	public static <L, R> PrismX<L, R, Optional<L>, Optional<R>> optional() {
+		return PrismX.of((opt) -> opt.isPresent() ? Either.right(opt.get()) : Either.left(Optional.empty()),
+				Optional::ofNullable);
+	}
+
+	/**
+	 * Create a prism that reflects on whether a double corresponds to a given
+	 * integer.
+	 * 
+	 * @return A prism on the int view of a double.
+	 */
+	public static Prism<Integer, Double> whole() {
+		return Prism.of((vl) -> Math.rint(vl) == vl ? Either.right(vl.intValue()) : Either.left(vl),
+				Integer::doubleValue);
+	}
+}
-- 
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