adding unification parameter to Profunctor

jnape · jnape · commit b51e93fb2c2b · 2017-01-21T14:46:20.000-06:00
diff --git a/src/main/java/com/jnape/palatable/lambda/functions/Fn1.java b/src/main/java/com/jnape/palatable/lambda/functions/Fn1.java
@@ -13,7 +13,7 @@
  * @param <B> The result type
  */
 @FunctionalInterface
-public interface Fn1<A, B> extends Functor<B, Fn1<A, ?>>, Profunctor<A, B>, Function<A, B> {
+public interface Fn1<A, B> extends Functor<B, Fn1<A, ?>>, Profunctor<A, B, Fn1>, Function<A, B> {
 
     /**
      * Invoke this function with the given argument.
diff --git a/src/main/java/com/jnape/palatable/lambda/functor/Profunctor.java b/src/main/java/com/jnape/palatable/lambda/functor/Profunctor.java
@@ -19,7 +19,7 @@
  * @see Fn1
  */
 @FunctionalInterface
-public interface Profunctor<A, B> {
+public interface Profunctor<A, B, PF extends Profunctor> {
 
     /**
      * Contravariantly map over the left parameter.
@@ -28,7 +28,7 @@ public interface Profunctor<A, B> {
      * @param fn  the mapping function
      * @return a profunctor over Z (the new left parameter type) and C (the same right parameter type)
      */
-    default <Z> Profunctor<Z, B> diMapL(Function<Z, A> fn) {
+    default <Z> Profunctor<Z, B, PF> diMapL(Function<Z, A> fn) {
         return diMap(fn, id());
     }
 
@@ -40,7 +40,7 @@ default <Z> Profunctor<Z, B> diMapL(Function<Z, A> fn) {
      * @param fn  the mapping function
      * @return a profunctor over A (the same left parameter type) and C (the new right parameter type)
      */
-    default <C> Profunctor<A, C> diMapR(Function<B, C> fn) {
+    default <C> Profunctor<A, C, PF> diMapR(Function<B, C> fn) {
         return diMap(id(), fn);
     }
 
@@ -54,5 +54,5 @@ default <C> Profunctor<A, C> diMapR(Function<B, C> fn) {
      * @param rFn the right parameter mapping function
      * @return a profunctor over Z (the new left parameter type) and C (the new right parameter type)
      */
-    <Z, C> Profunctor<Z, C> diMap(Function<Z, A> lFn, Function<B, C> rFn);
+    <Z, C> Profunctor<Z, C, PF> diMap(Function<Z, A> lFn, Function<B, C> rFn);
 }
diff --git a/src/test/java/com/jnape/palatable/lambda/functor/ProfunctorTest.java b/src/test/java/com/jnape/palatable/lambda/functor/ProfunctorTest.java
@@ -15,15 +15,15 @@ public class ProfunctorTest {
     @Test
     public void diMapLUsesIdentityForRightDiMapFunction() {
         AtomicReference<Function> rightInvocation = new AtomicReference<>();
-        Profunctor<String, Integer> profunctor = new InvocationRecordingProfunctor<>(new AtomicReference<>(), rightInvocation);
+        Profunctor<String, Integer, InvocationRecordingProfunctor> profunctor = new InvocationRecordingProfunctor<>(new AtomicReference<>(), rightInvocation);
         profunctor.diMapL(Object::toString);
         assertThat(rightInvocation.get(), is(id()));
     }
 
     @Test
     public void diMapRUsesIdentityForLeftDiMapFunction() {
         AtomicReference<Function> leftInvocation = new AtomicReference<>();
-        Profunctor<String, Integer> profunctor = new InvocationRecordingProfunctor<>(leftInvocation, new AtomicReference<>());
+        Profunctor<String, Integer, InvocationRecordingProfunctor> profunctor = new InvocationRecordingProfunctor<>(leftInvocation, new AtomicReference<>());
         profunctor.diMapR(String::valueOf);
         assertThat(leftInvocation.get(), is(id()));
     }
diff --git a/src/test/java/testsupport/applicatives/InvocationRecordingProfunctor.java b/src/test/java/testsupport/applicatives/InvocationRecordingProfunctor.java
@@ -5,7 +5,7 @@
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Function;
 
-public final class InvocationRecordingProfunctor<A, B> implements Profunctor<A, B> {
+public final class InvocationRecordingProfunctor<A, B> implements Profunctor<A, B, InvocationRecordingProfunctor> {
     private final AtomicReference<Function> leftFn;
     private final AtomicReference<Function> rightFn;
 
@@ -17,9 +17,9 @@ public InvocationRecordingProfunctor(AtomicReference<Function> leftFn,
 
     @Override
     @SuppressWarnings("unchecked")
-    public <C, D> Profunctor<C, D> diMap(Function<C, A> lFn, Function<B, D> rFn) {
+    public <C, D> InvocationRecordingProfunctor<C, D> diMap(Function<C, A> lFn, Function<B, D> rFn) {
         leftFn.set(lFn);
         rightFn.set(rFn);
-        return (Profunctor<C, D>) this;
+        return (InvocationRecordingProfunctor<C, D>) this;
     }
 }
