Added bimap method and unit tests

src/main/java/com/ceticamarco/lambdatonic/Either.java

@@ -64,6 +64,19 @@ public sealed interface Either<L, R> permits Left, Right {
      */
     <T> Either<L, T> map(Function<R, T> fn);
 
+    /**
+     * <p>
+     *     Applies <i>onLeft</i> function to the <i>Left</i> subtype or the
+     *     <i>onRight</i> function to the <i>Right</i> subtype.
+     * </p>
+     * @param onLeft The function to apply to the <i>Left</i> subtyp
+     * @param onRight The function to apply to the <i>Right</i> subtype
+     * @return An <i>Either</i> functor
+     * @param <T> The return type of the <i>onLeft</i> function
+     * @param <K> The return type of the <i>onRight</i> function
+     */
+    <T, K> Either<T, K> bimap(Function<L, T> onLeft, Function<R, K> onRight);
+
     /**
      * <p>
      *     Returns the content of <i>Right</i> or a default value
@@ -85,4 +98,5 @@ public sealed interface Either<L, R> permits Left, Right {
      * @return The left value of <i>Either</i> or the default value
      */
     L fromLeft(L defaultValue);
+
 }

src/main/java/com/ceticamarco/lambdatonic/Left.java

@@ -32,6 +32,11 @@ public record Left<L, R>(L value) implements Either<L, R> {
         return new Left<>(this.value);
     }
 
+    @Override
+    public <T, K> Either<T, K> bimap(Function<L, T> onLeft, Function<R, K> onRight) {
+        return new Left<>(onLeft.apply(this.value));
+    }
+
     @Override
     public R fromRight(R defaultValue) {
         return defaultValue;

src/main/java/com/ceticamarco/lambdatonic/Right.java

@@ -32,6 +32,11 @@ public record Right<L, R>(R value) implements Either<L, R> {
         return new Right<>(fn.apply(this.value));
     }
 
+    @Override
+    public <T, K> Either<T, K> bimap(Function<L, T> onLeft, Function<R, K> onRight) {
+        return new Right<>(onRight.apply(this.value));
+    }
+
     @Override
     public R fromRight(R defaultValue) {
         return this.value;

src/test/java/com/ceticamarco/lambdatonic/LeftTests.java

@@ -51,6 +51,16 @@ public class LeftTests {
         ), "Undefined variable");
     }
 
+    @Test
+    public void testFunctorBiMapLeft() {
+        Function<Integer, Integer> f = x -> x + 1;
+        Function<String, String> g = String::toUpperCase;
+
+        Either<Integer, String> actual = this.resEither.bimap(f, g);
+
+        assertEquals(actual.fromLeft(-1), 20);
+    }
+
     @Test
     public void testLeftFunctorIdentityMorphism() {
         // Applying the map function with the identity function,

src/test/java/com/ceticamarco/lambdatonic/RightTests.java

@@ -51,6 +51,16 @@ public class RightTests {
         ), 16);
     }
 
+    @Test
+    public void testFunctorBiMapRight() {
+        Function<Integer, Integer> f = x -> x + 1;
+        Function<String, String> g = String::toUpperCase;
+
+        Either<Integer, String> actual = this.resEither.bimap(f, g);
+
+        assertEquals(actual.fromRight("-1"), "QUERY EXECUTED SUCCESSFULLY");
+    }
+
     @Test
     public void testRightFunctorIdentityMorphism() {
         // Applying the map function with the identity function,