Merge pull request #260 from slnowak/support-for-either

Fixed for comprehension for javaslang.control.Either

Author: johnmcclean

cyclops-javaslang/src/main/java/com/aol/cyclops/javaslang/comprehenders/EitherComprehender.java

@@ -12,20 +12,17 @@
 public class EitherComprehender implements ValueComprehender<Either> {
 
     public Object filter(Either t, Predicate p) {
-        return t.right()
-                .filter(x -> p.test(x));
+        return t.filter(p);
     }
 
     @Override
     public Object map(Either t, Function fn) {
-        return t.right()
-                .map(e -> fn.apply(e));
+        return t.map(fn);
     }
 
     @Override
     public Object flatMap(Either t, Function fn) {
-        return t.right()
-                .flatMap(e -> fn.apply(e));
+        return t.flatMap(fn);
     }
 
     @Override
@@ -44,9 +41,6 @@ public Class getTargetClass() {
     }
 
     public Object resolveForCrossTypeFlatMap(Comprehender comp, Either apply) {
-        if (apply.isRight())
-            return comp.of(apply.right()
-                                .get());
-        return comp.empty();
+        return apply.isRight() ? comp.of(apply.get()) : comp.empty();
     }
 }

cyclops-javaslang/src/test/java/com/aol/cyclops/javaslang/EitherComprehensionTest.java

@@ -0,0 +1,123 @@
+package com.aol.cyclops.javaslang;
+
+import com.aol.cyclops.control.For;
+import javaslang.control.Either;
+import org.junit.Test;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+
+public class EitherComprehensionTest {
+
+    /*
+        def prepareCappuccino(): Either[Exception, String] = for {
+            ground <- grind("arabica beans")
+            water <- heatWater(Water(25))
+            espresso <- brew(ground, water)
+            foam <- frothMilk("milk")
+        } yield combine(espresso, foam)
+     */
+
+    private static final Exception AN_EXCEPTION = new RuntimeException();
+
+    @Test
+    public void shouldComprehendEitherExpressions() throws Exception {
+        // when
+        final Either<Exception, String> wrapsCappuccino = For
+                .iterable(grind("arabica beans"))
+                .iterable(ground -> heatWater(new Water(25)))
+                .iterable(ground -> water -> brew(ground, water))
+                .iterable(ground -> water -> espresso -> frothMilk("milk"))
+                .yield(ground -> water -> espresso -> foam -> combine(espresso, foam))
+                .unwrap();
+
+        // then
+        assertThat(
+                wrapsCappuccino.get(),
+                equalTo("cappuccino")
+        );
+    }
+
+    @Test
+    public void shouldComprehendEitherExpressionsWithFailedOne() throws Exception {
+        // when
+        final Either<Exception, String> wrapsException = For
+                .iterable(grind("arabica beans"))
+                .iterable(ground -> failToHeatWater(new Water(25)))
+                .iterable(ground -> water -> brew(ground, water))
+                .iterable(ground -> water -> espresso -> frothMilk("milk"))
+                .yield(ground -> water -> espresso -> foam -> combine(espresso, foam))
+                .unwrap();
+
+        // then
+        assertThat(
+                wrapsException.getLeft(),
+                equalTo(AN_EXCEPTION)
+        );
+    }
+
+    @Test
+    public void shouldComprehendEitherProjectionExpressions() throws Exception {
+        // when
+        final Either.RightProjection<Exception, String> wrapsCappuccino = For
+                .iterable(rightProjectionOf(grind("arabica beans")))
+                .iterable(ground -> rightProjectionOf(heatWater(new Water(25))))
+                .iterable(ground -> water -> rightProjectionOf(brew(ground, water)))
+                .iterable(ground -> water -> espresso -> rightProjectionOf(frothMilk("milk")))
+                .yield(ground -> water -> espresso -> foam -> combine(espresso, foam))
+                .unwrap();
+
+        // then
+        assertThat(
+                wrapsCappuccino.get(),
+                equalTo("cappuccino")
+        );
+    }
+
+    @Test
+    public void shouldComprehendEitherExpressionsMixedWithEitherProjectionExpressions() throws Exception {
+        // when
+        final Either<Exception, String> wrapsCappuccino = For
+                .iterable(grind("arabica beans"))
+                .iterable(ground -> heatWater(new Water(25)))
+                .iterable(ground -> water -> brew(ground, water))
+                .iterable(ground -> water -> espresso -> rightProjectionOf(frothMilk("milk")))
+                .yield(ground -> water -> espresso -> foam -> combine(espresso, foam))
+                .unwrap();
+
+        // then
+        assertThat(
+                wrapsCappuccino.get(),
+                equalTo("cappuccino")
+        );
+    }
+
+
+    Either<Exception, String> grind(String beans) {
+        return Either.right("ground " + beans);
+    }
+
+    Either<Exception, Water> heatWater(Water water) {
+        return Either.right(water.withTemperature(85));
+    }
+
+    Either<Exception, Water> failToHeatWater(Water water) {
+        return Either.left(AN_EXCEPTION);
+    }
+
+    Either<Exception, String> brew(String coffee, Water heatedWater) {
+        return Either.right("espresso");
+    }
+
+    Either<Exception, String> frothMilk(String milk) {
+        return Either.right("frothed " + milk);
+    }
+
+    String combine(String espresso, String frothedMilk) {
+        return "cappuccino";
+    }
+
+    private static <L, R> Either.RightProjection<L, R> rightProjectionOf(Either<L, R> either) {
+        return either.right();
+    }
+}