add group function to Seq (#2687)

Author: smthelusive

src/main/java/io/vavr/collection/Array.java

@@ -883,6 +883,11 @@ public <U> Array<U> flatMap(Function<? super T, ? extends Iterable<? extends U>>
         }
     }
 
+    @Override
+    public Seq<Array<T>> group() {
+        return Collections.group(this, Array::empty);
+    }
+
     @Override
     public <C> Map<C, Array<T>> groupBy(Function<? super T, ? extends C> classifier) {
         return io.vavr.collection.Collections.groupBy(this, classifier, Array::ofAll);

src/main/java/io/vavr/collection/CharSeq.java

@@ -558,6 +558,11 @@ public CharSeq flatMapChars(CharFunction<? extends CharSequence> mapper) {
         }
     }
 
+    @Override
+    public Seq<CharSeq> group() {
+        return Collections.group(this, CharSeq::empty);
+    }
+
     @Override
     public <C> Map<C, CharSeq> groupBy(Function<? super Character, ? extends C> classifier) {
         return io.vavr.collection.Collections.groupBy(this, classifier, CharSeq::ofAll);

src/main/java/io/vavr/collection/Collections.java

@@ -211,6 +211,13 @@ static <C extends Traversable<T>, T> C filterNot(C source, Predicate<? super T>
         }
     }
 
+    @SuppressWarnings("unchecked")
+    static <T, S extends Seq<T>> Seq<S> group(S source, Supplier<S> supplier) {
+        return source.foldLeft(HashMap.empty(), (Map<T, S> map, T value) ->
+                map.put(value, (S) map.getOrElse(value, supplier.get()).append(value)))
+                .map(entry -> entry._2);
+    }
+
     static <T, C, R extends Iterable<T>> Map<C, R> groupBy(Traversable<T> source, Function<? super T, ? extends C> classifier, Function<? super Iterable<T>, R> mapper) {
         Objects.requireNonNull(classifier, "classifier is null");
         Objects.requireNonNull(mapper, "mapper is null");

src/main/java/io/vavr/collection/IndexedSeq.java

@@ -152,9 +152,15 @@ default boolean endsWith(Seq<? extends T> that) {
     @Override
     <U> IndexedSeq<U> flatMap(Function<? super T, ? extends Iterable<? extends U>> mapper);
 
+    @Override
+    Seq<? extends IndexedSeq<T>> group();
+
     @Override
     <C> Map<C, ? extends IndexedSeq<T>> groupBy(Function<? super T, ? extends C> classifier);
 
+    @Override
+    Iterator<? extends IndexedSeq<T>> grouped(int size);
+
     @Override
     default int indexWhere(Predicate<? super T> predicate, int from) {
         Objects.requireNonNull(predicate, "predicate is null");
@@ -163,9 +169,6 @@ default int indexWhere(Predicate<? super T> predicate, int from) {
         return (n >= length()) ? -1 : n;
     }
 
-    @Override
-    Iterator<? extends IndexedSeq<T>> grouped(int size);
-
     @Override
     default int indexOfSlice(Iterable<? extends T> that, int from) {
         Objects.requireNonNull(that, "that is null");

src/main/java/io/vavr/collection/LinearSeq.java

@@ -129,6 +129,9 @@ public boolean isDefinedAt(Integer index) {
     @Override
     <U> LinearSeq<U> flatMap(Function<? super T, ? extends Iterable<? extends U>> mapper);
 
+    @Override
+    Seq<? extends LinearSeq<T>> group();
+
     @Override
     <C> Map<C, ? extends LinearSeq<T>> groupBy(Function<? super T, ? extends C> classifier);
 

src/main/java/io/vavr/collection/List.java

@@ -897,6 +897,11 @@ public final T apply(Integer index) {
         return list.head();
     }
 
+    @Override
+    public final Seq<List<T>> group() {
+        return Collections.group(this, List::empty);
+    }
+
     @Override
     public final <C> Map<C, List<T>> groupBy(Function<? super T, ? extends C> classifier) {
         return Collections.groupBy(this, classifier, List::ofAll);

src/main/java/io/vavr/collection/Queue.java

@@ -807,6 +807,11 @@ public T apply(Integer index) {
         }
     }
 
+    @Override
+    public Seq<Queue<T>> group() {
+        return Collections.group(this, Queue::empty);
+    }
+
     @Override
     public <C> Map<C, Queue<T>> groupBy(Function<? super T, ? extends C> classifier) {
         return io.vavr.collection.Collections.groupBy(this, classifier, Queue::ofAll);

src/main/java/io/vavr/collection/Seq.java

@@ -1196,6 +1196,13 @@ default <U> U foldRight(U zero, BiFunction<? super T, ? super U, ? extends U> f)
         return reverse().foldLeft(zero, (xs, x) -> f.apply(x, xs));
     }
 
+    /**
+     * Groups subsequent equal elements.
+     *
+     * @return a new Seq of new instances containing the equal elements.
+     */
+    Seq<? extends Seq<T>> group();
+
     @Override
     <C> Map<C, ? extends Seq<T>> groupBy(Function<? super T, ? extends C> classifier);
 

src/main/java/io/vavr/collection/Stream.java

@@ -1087,6 +1087,11 @@ public final T getOrElse(int index, T defaultValue) {
         return getOption(index).getOrElse(defaultValue);
     }
 
+    @Override
+    public final Seq<Stream<T>> group() {
+        return Collections.group(this, Stream::empty);
+    }
+
     @Override
     public final <C> Map<C, Stream<T>> groupBy(Function<? super T, ? extends C> classifier) {
         return io.vavr.collection.Collections.groupBy(this, classifier, Stream::ofAll);

src/main/java/io/vavr/collection/Vector.java

@@ -738,6 +738,11 @@ public T head() {
         }
     }
 
+    @Override
+    public Seq<Vector<T>> group() {
+        return Collections.group(this, Vector::empty);
+    }
+
     @Override
     public <C> Map<C, Vector<T>> groupBy(Function<? super T, ? extends C> classifier) { return io.vavr.collection.Collections.groupBy(this, classifier, Vector::ofAll); }