adding eq

jnape · jnape · commit f9b10be694d7 · 2016-11-12T16:05:31.000-06:00
diff --git a/src/main/java/com/jnape/palatable/lambda/functions/builtin/fn2/Eq.java b/src/main/java/com/jnape/palatable/lambda/functions/builtin/fn2/Eq.java
@@ -0,0 +1,32 @@
+package com.jnape.palatable.lambda.functions.builtin.fn2;
+
+import com.jnape.palatable.lambda.functions.Fn1;
+import com.jnape.palatable.lambda.functions.Fn2;
+
+/**
+ * Type-safe equality in function form; uses {@link Object#equals}, not <code>==</code>.
+ *
+ * @param <A> the type to compare for equality
+ */
+public final class Eq<A> implements Fn2<A, A, Boolean> {
+
+    private Eq() {
+    }
+
+    @Override
+    public Boolean apply(A x, A y) {
+        return x == null ? y == null : x.equals(y);
+    }
+
+    public static <A> Eq<A> eq() {
+        return new Eq<>();
+    }
+
+    public static <A> Fn1<A, Boolean> eq(A x) {
+        return Eq.<A>eq().apply(x);
+    }
+
+    public static <A> Boolean eq(A x, A y) {
+        return eq(x).apply(y);
+    }
+}
diff --git a/src/test/java/com/jnape/palatable/lambda/functions/builtin/fn2/EqTest.java b/src/test/java/com/jnape/palatable/lambda/functions/builtin/fn2/EqTest.java
@@ -0,0 +1,22 @@
+package com.jnape.palatable.lambda.functions.builtin.fn2;
+
+import org.junit.Test;
+
+import static com.jnape.palatable.lambda.functions.builtin.fn2.Eq.eq;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class EqTest {
+
+    @Test
+    public void testsValueEquality() {
+        Eq<String> stringEq = eq();
+
+        assertTrue(stringEq.apply("a", "a"));
+        assertFalse(stringEq.apply("a", "b"));
+        assertFalse(stringEq.apply("b", "a"));
+        assertTrue(stringEq.apply(null, null));
+        assertFalse(stringEq.apply("a", null));
+        assertFalse(stringEq.apply(null, "a"));
+    }
+}
