Merge pull request ReactiveX#137 from mairbek/ranges

Implemented range operator. Fixes issue ReactiveX#68

Author: benjchristensen

rxjava-core/src/main/java/rx/Observable.java

@@ -53,6 +53,7 @@
 import rx.operators.OperationZip;
 import rx.util.AtomicObservableSubscription;
 import rx.util.AtomicObserver;
+import rx.util.Range;
 import rx.util.functions.Action0;
 import rx.util.functions.Action1;
 import rx.util.functions.Func1;
@@ -547,6 +548,20 @@ public static <T> Observable<T> from(T... items) {
         return toObservable(items);
     }
 
+    /**
+     * Generates an observable sequence of integral numbers within a specified range.
+     *
+     * @param start The value of the first integer in the sequence
+     * @param count The number of sequential integers to generate.
+     *
+     * @return An observable sequence that contains a range of sequential integral numbers.
+     *
+     * @see <a href="http://msdn.microsoft.com/en-us/library/hh229460(v=vs.103).aspx">Observable.Range Method (Int32, Int32)</a>
+     */
+    public static Observable<Integer> range(int start, int count) {
+        return from(Range.createWithCount(start, count));
+    }
+
     /**
      * Returns an Observable that notifies an {@link Observer} of a single value and then completes.
      * <p>

rxjava-core/src/main/java/rx/util/Range.java

@@ -0,0 +1,107 @@
+/**
+ * Copyright 2013 Netflix, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package rx.util;
+
+import org.junit.Test;
+
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+
+public final class Range implements Iterable<Integer> {
+    private final int start;
+    private final int end;
+    private final int step;
+
+    public static Range createWithCount(int start, int count) {
+        return create(start, start * (count + 1));
+    }
+
+    public static Range create(int start, int end) {
+        return new Range(start, end, 1);
+    }
+
+    public static Range createWithStep(int start, int end, int step) {
+        return new Range(start, end, step);
+    }
+
+    private Range(int start, int end, int step) {
+        this.start = start;
+        this.end = end;
+        this.step = step;
+    }
+
+    @Override
+    public Iterator<Integer> iterator() {
+        return new Iterator<Integer>() {
+            private int current = start;
+
+            @Override
+            public boolean hasNext() {
+                return current < end;
+            }
+
+            @Override
+            public Integer next() {
+                if (!hasNext()) {
+                    throw new NoSuchElementException("No more elements");
+                }
+                int result = current;
+                current += step;
+                return result;
+            }
+
+            @Override
+            public void remove() {
+                throw new UnsupportedOperationException("Read only iterator");
+            }
+        };
+    }
+
+    @Override
+    public String toString() {
+        return "Range (" + start + ", " + end + "), step " + step;
+    }
+
+
+    public static class UnitTest {
+
+        @Test
+        public void testSimpleRange() {
+            assertEquals(Arrays.asList(1, 2, 3, 4), toList(Range.create(1, 5)));
+        }
+
+        @Test
+        public void testRangeWithStep() {
+            assertEquals(Arrays.asList(1, 3, 5, 7, 9), toList(Range.createWithStep(1, 10, 2)));
+        }
+
+        @Test
+        public void testRangeWithCount() {
+            assertEquals(Arrays.asList(1, 2, 3, 4, 5), toList(Range.createWithCount(1, 5)));
+        }
+
+
+        private static <T> List<T> toList(Iterable<T> iterable) {
+            List<T> result = new ArrayList<T>();
+            for (T element : iterable) {
+                result.add(element);
+            }
+            return result;
+        }
+
+    }
+}