Expand readme (#41)

README.md

@@ -17,20 +17,20 @@ Java's Stream API is a powerful tool for processing collections of data. However
 Whenever possible, the library follows Project Reactor's naming conventions.
 
 Provided `Gatherers`:
-- `MoreGatherers.last(int)`
-- `MoreGatherers.sampling(int)`
-- `MoreGatherers.zip(Iterator<T2>)`
-- `MoreGatherers.zip(Iterator<T2>, BiFunction<T1,T2>)`
-- `MoreGatherers.zip(Stream<T2>)`
-- `MoreGatherers.zip(Stream<T2>, BiFunction<T1,T2>)`
-- `MoreGatherers.zipWithIterable(Iterable<T2>)`
-- `MoreGatherers.zipWithIterable(Iterable<T2>, BiFunction<T1,T2>)`
-- `MoreGatherers.zipWithIndex()`
-- `MoreGatherers.zipWithIndex(BiFunction<Long,T>)`
-- `MoreGatherers.distinctBy(Function<T, R>)`
-- `MoreGatherers.distinctByKeepLast(Function<T, R>)`
-- `MoreGatherers.distinctUntilChanged()`
-- `MoreGatherers.distinctUntilChanged(Function<T, R>)`
+- `MoreGatherers.last(int)`: takes last `n` elements from the stream
+- `MoreGatherers.sampling(int)`: takes every `n`-th element from the stream
+- `MoreGatherers.zip(Iterator<T2>)`: zips `Stream` elements with elements from the provided `Iterator`
+- `MoreGatherers.zip(Iterator<T2>, BiFunction<T1,T2>)`: zips `Stream` elements with elements from the provided `Iterator` using a custom zipper function
+- `MoreGatherers.zip(Stream<T2>)`: zips `Stream` elements with elements from the provided `Stream`
+- `MoreGatherers.zip(Stream<T2>, BiFunction<T1,T2>)`: zips `Stream` elements with elements from the provided `Stream` using a custom zipper function
+- `MoreGatherers.zipWithIterable(Iterable<T2>)`: zips `Stream` elements with elements from the provided `Iterable`
+- `MoreGatherers.zipWithIterable(Iterable<T2>, BiFunction<T1,T2>)`: zips elements with elements from the provided `Iterable` using a custom zipper function
+- `MoreGatherers.zipWithIndex()`: zips `Stream` elements with their index
+- `MoreGatherers.zipWithIndex(BiFunction<Long,T>)`: zips `Stream` elements with their index using a custom zipper function
+- `MoreGatherers.distinctBy(Function<T, R>)`: takes distinct elements based on a key extractor function
+- `MoreGatherers.distinctByKeepLast(Function<T, R>)`: takes distinct elements based on a key extractor function, keeping the last occurrence
+- `MoreGatherers.distinctUntilChanged()`: takes elements until a change is detected
+- `MoreGatherers.distinctUntilChanged(Function<T, R>)`: takes elements until a change is detected based on a key extractor function
 
 ### Philosophy
 

src/main/java/com/pivovarit/gatherers/MoreGatherers.java

@@ -214,7 +214,7 @@ private MoreGatherers() {
      *
      * @return a {@link Gatherer} that pairs elements with their corresponding index
      */
-    public static <T> Gatherer<T, ?, Map.Entry<Long, T>> zipWithIndex() {
+    public static <T> Gatherer<T, ?, Map.Entry<T, Long>> zipWithIndex() {
         return new ZipWithIndexGatherer<>();
     }
 }

src/main/java/com/pivovarit/gatherers/ZipWithIndexGatherer.java

@@ -5,17 +5,17 @@
 import java.util.function.Supplier;
 import java.util.stream.Gatherer;
 
-record ZipWithIndexGatherer<T>() implements Gatherer<T, AtomicLong, Map.Entry<Long, T>> {
+record ZipWithIndexGatherer<T>() implements Gatherer<T, AtomicLong, Map.Entry<T, Long>> {
 
     @Override
     public Supplier<AtomicLong> initializer() {
         return AtomicLong::new;
     }
 
     @Override
-    public Integrator<AtomicLong, T, Map.Entry<Long, T>> integrator() {
+    public Integrator<AtomicLong, T, Map.Entry<T, Long>> integrator() {
         return Integrator.ofGreedy((state, element, downstream) -> {
-            downstream.push(Map.entry(state.getAndIncrement(), element));
+            downstream.push(Map.entry(element, state.getAndIncrement()));
             return true;
         });
     }

src/test/java/com/pivovarit/gatherers/blackbox/ZipWithIndexTest.java

@@ -20,9 +20,9 @@ void shouldZipWithIndex() {
         assertThat(Stream.of("a", "b", "c")
           .gather(zipWithIndex()))
           .containsExactly(
-            entry(0L, "a"),
-            entry(1L, "b"),
-            entry(2L, "c")
+            entry("a", 0L),
+            entry("b", 1L),
+            entry("c", 2L)
           );
     }
 }