[#54] takeWhile-implementation test; javaDoc update

amaembo · Jan 14, 2016 · 3e910c3 · 3e910c3
1 parent ae6a1f3
commit 3e910c3
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Showing 2 changed files with 13 additions and 5 deletions.
diff --git a/src/main/java/one/util/streamex/StreamEx.java b/src/main/java/one/util/streamex/StreamEx.java
@@ -1376,9 +1376,9 @@ public EntryStream<T, T> withFirst() {
 
     /**
      * Creates a new Stream which is the result of applying of the supplied
-     * mapper {@code BiFunction} to the first element of the current stream and
-     * the stream containing the rest elements. (If a mapped stream is
-     * {@code null} an empty stream is used, instead.)
+     * mapper {@code BiFunction} to the first element of the current stream
+     * (head) and the stream containing the rest elements (tail). If a mapped
+     * stream is {@code null} an empty stream is used, instead.
      * 
      * <p>
      * This is an <a href="package-summary.html#StreamOps">quasi-intermediate
@@ -1393,8 +1393,8 @@ public EntryStream<T, T> withFirst() {
      * <pre>{@code
      * // Returns lazily-generated stream which performs scanLeft operation on the input
      * static <T> StreamEx<T> scanLeft(StreamEx<T> input, BinaryOperator<T> operator) {
-     *     return input.withFirst((head, stream) -> scanLeft(stream.mapFirst(cur -> operator.apply(head, cur)), operator)
-     *           .prepend(head));
+     *     return input.headTail((head, tail) -> 
+     *         scanLeft(tail.mapFirst(cur -> operator.apply(head, cur)), operator).prepend(head));
      * }}</pre>
      * 
      * <p>

diff --git a/src/test/java/one/util/streamex/StreamExTest.java b/src/test/java/one/util/streamex/StreamExTest.java
@@ -1571,6 +1571,9 @@ public void testHeadTail() {
 
         streamEx(() -> StreamEx.iterate(1, x -> x + 1), s -> assertEquals(asList(1, 3, 6, 10, 15, 21, 28, 36, 45, 55,
             66, 78, 91), scanLeft(s.get(), Integer::sum).takeWhile(x -> x < 100).toList()));
+
+        streamEx(() -> StreamEx.iterate(1, x -> x + 1), s -> assertEquals(IntStreamEx.range(1, 100).boxed().toList(),
+            takeWhile(s.get(), x -> x < 100).toList()));
 
         // http://stackoverflow.com/q/34395943/4856258
         int[] input = { 1, 2, 3, -1, 3, -10, 9, 100, 1, 100, 0 };
@@ -1595,6 +1598,11 @@ private static <T> StreamEx<T> scanLeft(StreamEx<T> input, BinaryOperator<T> ope
         return input.headTail((head, stream) -> scanLeft(stream.mapFirst(cur -> operator.apply(head, cur)), operator)
                 .prepend(head));
     }
+
+    // takeWhile intermediate op implementation
+    private static <T> StreamEx<T> takeWhile(StreamEx<T> input, Predicate<T> predicate) {
+        return input.headTail((head, stream) -> predicate.test(head) ? takeWhile(stream, predicate).prepend(head) : null );
+    }
 
     @Test
     public void testHeadTailClose() {