From 4bdd2278a77358fe56432b02af25c0c312973290 Mon Sep 17 00:00:00 2001
From: Marco Cetica <email@marcocetica.com>
Date: Wed, 18 Sep 2024 12:03:10 +0200
Subject: [PATCH] Added fromRight/fromLeft methods and unit tests

---
 .../com/ceticamarco/lambdatonic/Either.java   | 22 +++++++++++++++++++
 .../com/ceticamarco/lambdatonic/Left.java     | 10 +++++++++
 .../com/ceticamarco/lambdatonic/Right.java    | 10 +++++++++
 .../ceticamarco/lambdatonic/LeftTests.java    | 10 +++++++++
 .../ceticamarco/lambdatonic/RightTests.java   | 10 +++++++++
 5 files changed, 62 insertions(+)

diff --git a/src/main/java/com/ceticamarco/lambdatonic/Either.java b/src/main/java/com/ceticamarco/lambdatonic/Either.java
index f6d1b6d..4004613 100644
--- a/src/main/java/com/ceticamarco/lambdatonic/Either.java
+++ b/src/main/java/com/ceticamarco/lambdatonic/Either.java
@@ -63,4 +63,26 @@ public sealed interface Either<L, R> permits Left, Right {
      * @param <T> The return type of the <i>fn</i> function
      */
     <T> Either<L, T> map(Function<R, T> fn);
+
+    /**
+     * <p>
+     *     Returns the content of <i>Right</i> or a default value
+     *     <br /><br />
+     *     The default value must be of the same type of the <i>Right</i> value
+     * </p>
+     * @param defaultValue The default value to return if <i>Either</i> is <i>Left</i>
+     * @return The right value of <i>Either</i> or the default value
+     */
+    R fromRight(R defaultValue);
+
+    /**
+     * <p>
+     *     Returns the content of <i>Left</i> or a default value
+     *     <br /><br />
+     *     The default value must be of the same type of the <i>Left</i> value
+     * </p>
+     * @param defaultValue The default value to return if <i>Either</i> is <i>Right</i>
+     * @return The left value of <i>Either</i> or the default value
+     */
+    L fromLeft(L defaultValue);
 }
\ No newline at end of file
diff --git a/src/main/java/com/ceticamarco/lambdatonic/Left.java b/src/main/java/com/ceticamarco/lambdatonic/Left.java
index 8ee74a5..5d70761 100644
--- a/src/main/java/com/ceticamarco/lambdatonic/Left.java
+++ b/src/main/java/com/ceticamarco/lambdatonic/Left.java
@@ -31,4 +31,14 @@ public record Left<L, R>(L value) implements Either<L, R> {
     public <T> Either<L, T> map(Function<R, T> fn) {
         return new Left<>(this.value);
     }
+
+    @Override
+    public R fromRight(R defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public L fromLeft(L defaultValue) {
+        return this.value;
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/ceticamarco/lambdatonic/Right.java b/src/main/java/com/ceticamarco/lambdatonic/Right.java
index 4bce7e3..d154c28 100644
--- a/src/main/java/com/ceticamarco/lambdatonic/Right.java
+++ b/src/main/java/com/ceticamarco/lambdatonic/Right.java
@@ -31,4 +31,14 @@ public record Right<L, R>(R value) implements Either<L, R> {
     public <T> Either<L, T> map(Function<R, T> fn) {
         return new Right<>(fn.apply(this.value));
     }
+
+    @Override
+    public R fromRight(R defaultValue) {
+        return this.value;
+    }
+
+    @Override
+    public L fromLeft(L defaultValue) {
+        return defaultValue;
+    }
 }
\ No newline at end of file
diff --git a/src/test/java/com/ceticamarco/lambdatonic/LeftTests.java b/src/test/java/com/ceticamarco/lambdatonic/LeftTests.java
index ac15d70..3610933 100644
--- a/src/test/java/com/ceticamarco/lambdatonic/LeftTests.java
+++ b/src/test/java/com/ceticamarco/lambdatonic/LeftTests.java
@@ -74,4 +74,14 @@ public class LeftTests {
 
         assertEquals(composition, FGMapped);
     }
+
+    @Test
+    public void testFromRightOnLeft() {
+        assertEquals(this.numEither.fromRight(-1), -1);
+    }
+
+    @Test
+    public void testFromLeftOnLeft() {
+        assertEquals(this.resEither.fromLeft(-1), 19);
+    }
 }
diff --git a/src/test/java/com/ceticamarco/lambdatonic/RightTests.java b/src/test/java/com/ceticamarco/lambdatonic/RightTests.java
index f23f9ab..78abf89 100644
--- a/src/test/java/com/ceticamarco/lambdatonic/RightTests.java
+++ b/src/test/java/com/ceticamarco/lambdatonic/RightTests.java
@@ -74,4 +74,14 @@ public class RightTests {
 
         assertEquals(composition, FGMapped);
     }
+
+    @Test
+    public void testFromRightOnRight() {
+        assertEquals(this.numEither.fromRight(-1), 4);
+    }
+
+    @Test
+    public void testFromLeftOnRight() {
+        assertEquals(this.resEither.fromLeft(-1), -1);
+    }
 }