refactor: Add xor

Author: MarcellPerger1

src/main/java/net/marcellperger/mathexpr/util/rs/Option.java

@@ -13,6 +13,7 @@
 import java.util.stream.Stream;
 
 public sealed interface Option<T> extends Iterable<T> {
+    // hashCode, equals are automatically implemented for `record`s
     record Some<T>(T value) implements Option<T> {
         @Contract(pure = true)
         @Override
@@ -169,7 +170,16 @@ default Option<T> filter(Predicate<? super T> predicate) {
         };
     }
 
+    default Option<T> xor(Option<T> right) {
+        return switch (this) {  // I wish this implementation was more elegant
+            case Some<T> left -> right.isNone() ? left : newNone();
+            case None() -> right;
+        };
+    }
+
     // no insert / get_or_insert(_*) / take(_if) / replace
-    // (as record is immutable in Java)
-    // TODO check Rust docs
+    //  (as record is immutable in Java)
+    // no (un)zip(_with) because no tuples  in Java (will do if needed tho)
+    // rest are `impl`s on compound types which Java can't do
+    //  (see Result.java for detailed explanation), can do static method if we need it so much
 }

src/test/java/net/marcellperger/mathexpr/util/rs/OptionTest.java

@@ -298,7 +298,7 @@ void filter() {
     void or() {
         assertEquals(getSome(), getSome().or(Option.newSome(271)));
         assertEquals(getSome(), getSome().or(getNone()));
-        assertEquals(Option.newSome(271), getNone().or(Option.newSome(271)));
+        assertEquals(getSome(), getNone().or(getSome()));
         assertEquals(getNone(), getNone().or(getNone()));
     }
 
@@ -321,4 +321,12 @@ void orElse() {
             mNone.assertCalledOnce();
         }
     }
+
+    @Test
+    void xor() {
+        assertEquals(getNone(), getSome().xor(Option.newSome(271)));
+        assertEquals(getSome(), getSome().xor(getNone()));
+        assertEquals(getSome(), getNone().xor(getSome()));
+        assertEquals(getNone(), getNone().xor(getNone()));
+    }
 }