Merge pull request #1684 from ashrko619/scan-methods

Reimplemented Collections.scan methods
vavr-io · Nov 23, 2016 · 765071b · 765071b
2 parents 507654a + c8c3ef5
commit 765071b
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Showing 22 changed files with 63 additions and 96 deletions.
diff --git a/javaslang/src/main/java/javaslang/collection/AbstractMultimap.java b/javaslang/src/main/java/javaslang/collection/AbstractMultimap.java
@@ -405,7 +405,7 @@ public M retainAll(Iterable<? extends Tuple2<K, V>> elements) {
     @Override
     public M scan(Tuple2<K, V> zero, BiFunction<? super Tuple2<K, V>, ? super Tuple2<K, V>, ? extends Tuple2<K, V>> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return (M) Collections.scanLeft(this, zero, operation, Queue.empty(), Queue::append, this::createFromEntries);
+        return (M) Collections.scanLeft(this, zero, operation, this::createFromEntries);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Array.java b/javaslang/src/main/java/javaslang/collection/Array.java
@@ -1052,17 +1052,13 @@ public Array<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> opera
     @Override
     public <U> Array<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(this, zero, operation,
-                new java.util.ArrayList<>(), (c, u) -> {
-                    c.add(u);
-                    return c;
-                }, Array::ofAll);
+        return Collections.scanLeft(this, zero, operation, Array::ofAll);
     }
 
     @Override
     public <U> Array<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, List.empty(), List::prepend, Value::toArray);
+        return Collections.scanRight(this, zero, operation, Array::ofAll);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/BitSet.java b/javaslang/src/main/java/javaslang/collection/BitSet.java
@@ -469,18 +469,12 @@ default BitSet<T> retainAll(Iterable<? extends T> elements) {
 
     @Override
     default <U> Set<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
-        return Collections.scanLeft(this, zero, operation, new java.util.ArrayList<>(), (c, u) -> {
-            c.add(u);
-            return c;
-        }, HashSet::ofAll);
+        return Collections.scanLeft(this, zero, operation, HashSet::ofAll);
     }
 
     @Override
     default <U> Set<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
-        return Collections.scanRight(this, zero, operation, new java.util.ArrayList<>(), (c, u) -> {
-            c.add(u);
-            return c;
-        }, HashSet::ofAll);
+        return Collections.scanRight(this, zero, operation, HashSet::ofAll);
     }
 
     @Override
@@ -728,10 +722,7 @@ public Tuple2<BitSet<T>, BitSet<T>> span(Predicate<? super T> predicate) {
         @Override
         public BitSet<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> operation) {
             Objects.requireNonNull(operation, "operation is null");
-            return Collections.scanLeft(this, zero, operation, new java.util.ArrayList<>(), (arr, t) -> {
-                arr.add(t);
-                return arr;
-            }, this::createFromAll);
+            return Collections.scanLeft(this, zero, operation, this::createFromAll);
         }
 
         @Override

diff --git a/javaslang/src/main/java/javaslang/collection/CharSeq.java b/javaslang/src/main/java/javaslang/collection/CharSeq.java
@@ -802,20 +802,20 @@ public CharSeq reverse() {
     }
 
     @Override
-    public IndexedSeq<Character> scan(Character zero, BiFunction<? super Character, ? super Character, ? extends Character> operation) {
-        return scanLeft(zero, operation);
+    public CharSeq scan(Character zero, BiFunction<? super Character, ? super Character, ? extends Character> operation) {
+        return Collections.scanLeft(this, zero, operation, Iterator::toCharSeq);
     }
 
     @Override
     public <U> IndexedSeq<U> scanLeft(U zero, BiFunction<? super U, ? super Character, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(this, zero, operation, Vector.empty(), Vector::append, Function.identity());
+        return Collections.scanLeft(this, zero, operation, Iterator::toVector);
     }
 
     @Override
     public <U> IndexedSeq<U> scanRight(U zero, BiFunction<? super Character, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, Vector.empty(), Vector::prepend, Function.identity());
+        return Collections.scanRight(this, zero, operation, Iterator::toVector);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Collections.java b/javaslang/src/main/java/javaslang/collection/Collections.java
@@ -110,25 +110,18 @@ static int hash(Iterable<?> iterable) {
         return hashCode;
     }
 
-    static <T, U, C extends Iterable<U>, R extends Traversable<U>> R scanLeft(Iterable<? extends T> elements,
-                                                                              U zero, BiFunction<? super U, ? super T, ? extends U> operation,
-                                                                              C cumulativeResult, BiFunction<C, U, C> combiner,
-                                                                              Function<C, R> finisher) {
-        U acc = zero;
-        cumulativeResult = combiner.apply(cumulativeResult, acc);
-        for (T a : elements) {
-            acc = operation.apply(acc, a);
-            cumulativeResult = combiner.apply(cumulativeResult, acc);
-        }
-        return finisher.apply(cumulativeResult);
+    static <T, U, R extends Traversable<U>> R scanLeft(Traversable<? extends T> traversable,
+                                                       U zero, BiFunction<? super U, ? super T, ? extends U> operation, Function<Iterator<U>, R> finisher) {
+
+        final Iterator<U> iterator = traversable.iterator().scanLeft(zero, operation);
+        return finisher.apply(iterator);
     }
 
-    static <T, U, C extends Iterable<U>, R extends Traversable<U>> R scanRight(Iterable<? extends T> elements,
-                                                                               U zero, BiFunction<? super T, ? super U, ? extends U> operation,
-                                                                               C cumulativeResult, BiFunction<C, U, C> combiner,
-                                                                               Function<C, R> finisher) {
-        final Iterator<? extends T> reversedElements = reverseIterator(elements);
-        return scanLeft(reversedElements, zero, (u, t) -> operation.apply(t, u), cumulativeResult, combiner, finisher);
+    static <T, U, R extends Traversable<U>> R scanRight(Traversable<? extends T> traversable,
+                                                        U zero, BiFunction<? super T, ? super U, ? extends U> operation, Function<Iterator<U>, R> finisher) {
+
+        final Iterator<? extends T> reversedElements = reverseIterator(traversable);
+        return scanLeft(reversedElements, zero, (u, t) -> operation.apply(t, u), us -> finisher.apply(reverseIterator(us)));
     }
 
     @SuppressWarnings("unchecked")
@@ -137,7 +130,7 @@ static <T, S extends Seq<T>> Iterator<S> crossProduct(S empty, S seq, int power)
             return Iterator.empty();
         }
         return Iterator.range(0, power)
-                       .foldLeft(Iterator.of(empty), (product, ignored) -> product.flatMap(el -> seq.map(t -> (S) el.append(t))));
+                .foldLeft(Iterator.of(empty), (product, ignored) -> product.flatMap(el -> seq.map(t -> (S) el.append(t))));
     }
 
     static <C extends Traversable<T>, T> C tabulate(int n, Function<? super Integer, ? extends T> f, C empty, Function<T[], C> of) {
@@ -213,7 +206,7 @@ static <T> boolean isTraversableAgain(Iterable<? extends T> iterable) {
     }
 
     @SuppressWarnings("unchecked")
-    static <T> Iterator<? extends T> reverseIterator(Iterable<? extends T> iterable) {
+    static <T> Iterator<T> reverseIterator(Iterable<T> iterable) {
         if (iterable instanceof java.util.List) {
             final java.util.List<T> list = (java.util.List<T>) iterable;
             return new Iterator<T>() {
@@ -225,10 +218,10 @@ static <T> Iterator<? extends T> reverseIterator(Iterable<? extends T> iterable)
                 @Override
                 public T next() { return delegate.previous(); }
             };
+        } else if (iterable instanceof Seq) {
+            return ((Seq<T>) iterable).reverseIterator();
         } else {
-            final Seq<? extends T> result = (iterable instanceof Seq) ? (Seq<T>) iterable
-                                                                      : Vector.ofAll(iterable);
-            return result.reverseIterator();
+            return List.<T>empty().pushAll(iterable).iterator();
         }
     }
 }
diff --git a/javaslang/src/main/java/javaslang/collection/HashMap.java b/javaslang/src/main/java/javaslang/collection/HashMap.java
@@ -707,7 +707,7 @@ public HashMap<K, V> retainAll(Iterable<? extends Tuple2<K, V>> elements) {
     public HashMap<K, V> scan(
             Tuple2<K, V> zero,
             BiFunction<? super Tuple2<K, V>, ? super Tuple2<K, V>, ? extends Tuple2<K, V>> operation) {
-        return Maps.scan(this, HashMap::empty, zero, operation);
+        return Maps.scan(this, zero, operation, this::createFromEntries);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/HashSet.java b/javaslang/src/main/java/javaslang/collection/HashSet.java
@@ -716,16 +716,13 @@ public HashSet<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> ope
     @Override
     public <U> HashSet<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(this, zero, operation, new java.util.ArrayList<>(), (c, u) -> {
-            c.add(u);
-            return c;
-        }, HashSet::ofAll);
+        return Collections.scanLeft(this, zero, operation, HashSet::ofAll);
     }
 
     @Override
     public <U> HashSet<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, HashSet.empty(), HashSet::add, Function.identity());
+        return Collections.scanRight(this, zero, operation, HashSet::ofAll);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Iterator.java b/javaslang/src/main/java/javaslang/collection/Iterator.java
@@ -1772,7 +1772,7 @@ default <U> Iterator<U> scanRight(U zero, BiFunction<? super T, ? super U, ? ext
         if (isEmpty()) {
             return of(zero);
         } else {
-            return Collections.scanRight(this, zero, operation, Stream.empty(), Stream::prepend, Stream::iterator);
+            return Collections.scanRight(this, zero, operation, Function.identity());
         }
     }
 

diff --git a/javaslang/src/main/java/javaslang/collection/LinkedHashMap.java b/javaslang/src/main/java/javaslang/collection/LinkedHashMap.java
@@ -760,7 +760,7 @@ public LinkedHashMap<K, V> retainAll(Iterable<? extends Tuple2<K, V>> elements)
     public LinkedHashMap<K, V> scan(
             Tuple2<K, V> zero,
             BiFunction<? super Tuple2<K, V>, ? super Tuple2<K, V>, ? extends Tuple2<K, V>> operation) {
-        return Maps.scan(this, LinkedHashMap::empty, zero, operation);
+        return Maps.scan(this, zero, operation, this::createFromEntries);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/LinkedHashSet.java b/javaslang/src/main/java/javaslang/collection/LinkedHashSet.java
@@ -715,16 +715,13 @@ public LinkedHashSet<T> scan(T zero, BiFunction<? super T, ? super T, ? extends
     @Override
     public <U> LinkedHashSet<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(this, zero, operation, new java.util.ArrayList<>(), (c, u) -> {
-            c.add(u);
-            return c;
-        }, LinkedHashSet::ofAll);
+        return Collections.scanLeft(this, zero, operation, LinkedHashSet::ofAll);
     }
 
     @Override
     public <U> LinkedHashSet<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, List.empty(), List::prepend, LinkedHashSet::ofAll);
+        return Collections.scanRight(this, zero, operation, LinkedHashSet::ofAll);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/List.java b/javaslang/src/main/java/javaslang/collection/List.java
@@ -1176,13 +1176,13 @@ default List<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> opera
     @Override
     default <U> List<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(this, zero, operation, empty(), List::prepend, List::reverse);
+        return Collections.scanLeft(this, zero, operation, Iterator::toList);
     }
 
     @Override
     default <U> List<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, empty(), List::prepend, Function.identity());
+        return Collections.scanRight(this, zero, operation, Iterator::toList);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Map.java b/javaslang/src/main/java/javaslang/collection/Map.java
@@ -503,13 +503,13 @@ default <U> Seq<U> map(Function<? super Tuple2<K, V>, ? extends U> mapper) {
     @Override
     default <U> Seq<U> scanLeft(U zero, BiFunction<? super U, ? super Tuple2<K, V>, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return iterator().scanLeft(zero, operation).toStream();
+        return Collections.scanLeft(this, zero, operation, Iterator::toVector);
     }
 
     @Override
     default <U> Seq<U> scanRight(U zero, BiFunction<? super Tuple2<K, V>, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, Stream.empty(), Stream::prepend, Function.identity());
+        return Collections.scanRight(this, zero, operation, Iterator::toVector);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Maps.java b/javaslang/src/main/java/javaslang/collection/Maps.java
@@ -255,11 +255,12 @@ static <K, V, M extends Map<K, V>> M replaceAll(M map, BiFunction<? super K, ? s
         return (M) map.map((k, v) -> Tuple(k, function.apply(k, v)));
     }
 
-    static <K, V, M extends Map<K, V>> M scan(
-            M map, Supplier<M> emptySupplier, Tuple2<K, V> zero,
-            BiFunction<? super Tuple2<K, V>, ? super Tuple2<K, V>, ? extends Tuple2<K, V>> operation) {
+    @SuppressWarnings("unchecked")
+    static <K, V, M extends Map<K, V>> M scan(M map, Tuple2<K, V> zero,
+                                              BiFunction<? super Tuple2<K, V>, ? super Tuple2<K, V>, ? extends Tuple2<K, V>> operation,
+                                              Function<Iterator<Tuple2<K, V>>, Traversable<Tuple2<K, V>>> finisher) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(map, zero, operation, emptySupplier.get(), Maps::put, Function.identity());
+        return (M) Collections.scanLeft(map, zero, operation, finisher);
     }
 
     static <K, V, M extends Map<K, V>> Iterator<M> sliding(M map, OfEntries<K, V, M> ofEntries, int size) {

diff --git a/javaslang/src/main/java/javaslang/collection/Multimap.java b/javaslang/src/main/java/javaslang/collection/Multimap.java
@@ -415,13 +415,13 @@ default <U> Seq<U> map(Function<? super Tuple2<K, V>, ? extends U> mapper) {
     @Override
     default <U> Seq<U> scanLeft(U zero, BiFunction<? super U, ? super Tuple2<K, V>, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return iterator().scanLeft(zero, operation).toStream();
+        return Collections.scanLeft(this, zero, operation, Iterator::toVector);
     }
 
     @Override
     default <U> Seq<U> scanRight(U zero, BiFunction<? super Tuple2<K, V>, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, Stream.empty(), Stream::prepend, Function.identity());
+        return Collections.scanRight(this, zero, operation, Iterator::toVector);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/PriorityQueue.java b/javaslang/src/main/java/javaslang/collection/PriorityQueue.java
@@ -438,19 +438,19 @@ public PriorityQueue<T> replaceAll(T currentElement, T newElement) {
 
     @Override
     public PriorityQueue<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> operation) {
-        return Collections.scanLeft(this, zero, operation, empty(comparator), PriorityQueue::enqueue, Function.identity());
+        return Collections.scanLeft(this, zero, operation, it -> ofAll(comparator, it));
     }
 
     @Override
     public <U> PriorityQueue<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(this, zero, operation, empty(naturalComparator()), PriorityQueue::enqueue, Function.identity());
+        return Collections.scanLeft(this, zero, operation, it -> ofAll(naturalComparator(), it));
     }
 
     @Override
     public <U> PriorityQueue<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, empty(naturalComparator()), PriorityQueue::enqueue, Function.identity());
+        return Collections.scanRight(this, zero, operation, it -> ofAll(naturalComparator(), it));
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Queue.java b/javaslang/src/main/java/javaslang/collection/Queue.java
@@ -961,15 +961,13 @@ public Queue<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> opera
     @Override
     public <U> Queue<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        // prepends to the rear-list in O(1)
-        return Collections.scanLeft(this, zero, operation, empty(), Queue::append, Function.identity());
+        return Collections.scanLeft(this, zero, operation, Iterator::toQueue);
     }
 
     @Override
     public <U> Queue<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
-        // add elements in reverse order in O(1) and creates a Queue instance in O(1)
-        final List<U> list = Collections.scanRight(this, zero, operation, List.empty(), List::prepend, Function.identity());
-        return ofAll(list);
+        Objects.requireNonNull(operation, "operation is null");
+        return Collections.scanRight(this, zero, operation, Iterator::toQueue);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Stream.java b/javaslang/src/main/java/javaslang/collection/Stream.java
@@ -1242,14 +1242,14 @@ default Stream<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> ope
     default <U> Stream<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
         // lazily streams the elements of an iterator
-        return Stream.ofAll(iterator().scanLeft(zero, operation));
+        return Collections.scanLeft(this, zero, operation, Iterator::toStream);
     }
 
     // not lazy!
     @Override
     default <U> Stream<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, Stream.empty(), Stream::prepend, Function.identity());
+        return Collections.scanRight(this, zero, operation, Iterator::toStream);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/Tree.java b/javaslang/src/main/java/javaslang/collection/Tree.java
@@ -532,13 +532,13 @@ default Seq<T> scan(T zero, BiFunction<? super T, ? super T, ? extends T> operat
     @Override
     default <U> Seq<U> scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanLeft(this, zero, operation, List.empty(), List::prepend, List::reverse);
+        return Collections.scanLeft(this, zero, operation, Iterator::toStream);
     }
 
     @Override
     default <U> Seq<U> scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation) {
         Objects.requireNonNull(operation, "operation is null");
-        return Collections.scanRight(this, zero, operation, List.empty(), List::prepend, Function.identity());
+        return Collections.scanRight(this, zero, operation, Iterator::toStream);
     }
 
     @Override

diff --git a/javaslang/src/main/java/javaslang/collection/TreeMap.java b/javaslang/src/main/java/javaslang/collection/TreeMap.java
@@ -1080,7 +1080,7 @@ public TreeMap<K, V> retainAll(Iterable<? extends Tuple2<K, V>> elements) {
     public TreeMap<K, V> scan(
             Tuple2<K, V> zero,
             BiFunction<? super Tuple2<K, V>, ? super Tuple2<K, V>, ? extends Tuple2<K, V>> operation) {
-        return Maps.scan(this, this::emptyInstance, zero, operation);
+        return Maps.scan(this, zero, operation, this::createFromEntries);
     }
 
     @Override