Merge pull request #166 from mperry/issue162

mperry · mperry · commit bd3c4c645f33 · 2015-07-03T23:03:57.000+10:00
Fixes #162, fix Validation.sequence and rename to sequenceReduce
diff --git a/core/src/main/java/fj/data/Validation.java b/core/src/main/java/fj/data/Validation.java
@@ -801,19 +801,19 @@ public <B, C, D> Validation<List<E>, D> accumulate(Validation<E, B> v2, Validati
         }
     }
 
-
-
-    public static <A, E> Validation<List<E>, List<A>> sequence(List<Validation<E, A>> list) {
-        F2<Validation<E, A>, Validation<List<E>, List<A>>, Validation<List<E>, List<A>>> f2 = (v, acc) -> {
-            if (acc.isFail() && v.isFail()) {
-                return Validation.validation(acc.toEither().left().map(l -> l.cons(v.fail())));
-            } else if (acc.isSuccess() && v.isSuccess()) {
-                return acc.map(l -> l.cons(v.success()));
-            } else {
-                return acc;
-            }
-        };
-        return list.foldRight(f2, Validation.success(List.nil()));
+  /**
+   * If the list contains a failure, returns a Validation of the fails in the
+   * list, otherwise returns a successful Validation with the list of
+   * successful values.
+   */
+    public static <A, E> Validation<List<E>, List<A>> sequenceReduce(List<Validation<E, A>> list) {
+      if (list.exists(v -> v.isFail())) {
+        F2<List<E>, Validation<E, A>, List<E>> f = (acc, v) -> acc.cons(v.fail());
+        return Validation.fail(list.filter(v -> v.isFail()).foldLeft(f, List.nil()).reverse());
+      } else {
+        F2<List<A>, Validation<E, A>, List<A>> f = (acc, v) -> acc.cons(v.success());
+        return Validation.success(list.filter(v -> v.isSuccess()).foldLeft(f, List.nil()).reverse());
+      }
     }
 
     public <C> List<Validation<E, C>> traverseList(F<T, List<C>> f){
diff --git a/props-core/src/test/java/fj/data/properties/ValidationProperties.java b/props-core/src/test/java/fj/data/properties/ValidationProperties.java
@@ -5,13 +5,12 @@
 import fj.data.Validation;
 import fj.test.Arbitrary;
 import fj.test.Property;
-import fj.test.reflect.CheckParams;
 import fj.test.runner.PropertyTestRunner;
-import org.junit.Assert;
-import org.junit.Test;
 import org.junit.runner.RunWith;
 
 import static fj.test.Arbitrary.*;
+import static fj.test.Property.implies;
+import static fj.test.Property.prop;
 
 /**
  * Created by MarkPerry on 3/07/2015.
@@ -26,7 +25,23 @@ public Property partition() {
             boolean b1 = p._1().length() + p._2().length() == list.length();
             boolean b2 = p._1().map(s -> Validation.<String, Integer>fail(s)).equals(list.filter(v -> v.isFail()));
             boolean b3 = p._2().map(s -> Validation.<String, Integer>success(s)).equals(list.filter(v -> v.isSuccess()));
-            return Property.prop(b1 && b2 && b3);
+            return prop(b1 && b2 && b3);
+        });
+    }
+
+    public Property sequenceReduce() {
+        Arbitrary<List<Validation<String, Integer>>> al = arbList(arbValidation(arbUSASCIIString, arbInteger));
+        return Property.property(al, list -> {
+            Validation<List<String>, List<Integer>> v = Validation.sequenceReduce(list);
+            Property p1 = implies(
+                    list.exists(v1 -> v1.isFail()),
+                    () -> prop(v.fail().equals(list.filter(v2 -> v2.isFail()).map(v2 -> v2.fail())))
+            );
+            Property p2 = implies(
+                    list.forall(v1 -> v1.isSuccess()),
+                    () -> prop(v.success().equals(list.filter(v2 -> v2.isSuccess()).map(v2 -> v2.success())))
+            );
+            return p1.and(p2);
         });
     }
 
