First upload

.gitignore

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+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store
+
+### IntelliJ ###
+.idea/

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.ceticamarco</groupId>
+    <artifactId>LambdaTonic</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>22</maven.compiler.source>
+        <maven.compiler.target>22</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

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

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+package com.ceticamarco;
+
+import java.util.function.Function;
+
+/**
+ * <p>
+ *     This protocol defines a new sum type and provides the methods
+ *     to operate on the associated data.
+ *     The <i>Either</i> type can be implemented only by the <i>Left</i>
+ *     and the <i>Right</i> classes.
+ * </p>
+ * @param <L> The left type, representing the error value
+ * @param <R> The right type, representing the actual value
+ */
+public sealed interface Either<L, R> permits Left, Right {
+    <T> T match(Function<L, T> onLeft, Function<R, T> onRight);
+}

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

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+package com.ceticamarco;
+
+import java.util.function.Function;
+
+/**
+ * <p>
+ *
+ * </p>
+ * @param value
+ * @param <L>
+ * @param <R>
+ */
+public record Left<L, R>(L value) implements Either<L, R> {
+    @Override
+    public <T> T match(Function<L, T> onLeft, Function<R, T> onRight) {
+        return onLeft.apply(this.value);
+    }
+}

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

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+package com.ceticamarco;
+
+import java.util.function.Function;
+
+public record Right<L, R>(R value) implements Either<L, R> {
+    @Override
+    public <T> T match(Function<L, T> onLeft, Function<R, T> onRight) {
+        return onRight.apply(this.value);
+    }
+}