Added new version of reduce.

sdk/lib/async/stream.dart

Index: sdk/lib/async/stream.dart
diff --git a/sdk/lib/async/stream.dart b/sdk/lib/async/stream.dart
index c1699f0d636b1a22025551fcd36f9d5ccc4f3674..5224acf6abde146789edae26512cc4914b5af399 100644
--- a/sdk/lib/async/stream.dart
+++ b/sdk/lib/async/stream.dart
@@ -253,12 +253,35 @@ abstract class Stream<T> {
 
   /**
    * Reduces a sequence of values by repeatedly applying [combine].
-   *
-   * *WARNING UPCOMING API-CHANGE*: This method will be changed so that
-   * it doesn't take an initial value. Use [fold] instead.
    */
-  Future reduce(var initialValue, combine(var previous, T element)) {
-    return fold(initialValue, combine);
+  Future<T> reduce(T combine(T previous, T element)) {
+    _FutureImpl<T> result = new _FutureImpl<T>();
+    bool seenFirst = false;
+    T value;
+    StreamSubscription subscription = this.listen(
+      // TODO(ahe): Restore type when feature is implemented in dart2js
+      // checked mode. http://dartbug.com/7733
+      (/* T */ element) {
+        if (seenFirst) {
+          _runUserCode(() => combine(value, element),
+                       (T newValue) { value = newValue; },
+                       _cancelAndError(subscription, result));
+        } else {
+          value = element;
+          seenFirst = true;
+        }
+      },
+      onError: result._setError,
+      onDone: () {
+        if (!seenFirst) {
+          result._setError(new StateError("No elements"));
+        } else {
+          result._setValue(value);
+        }
+      },
+      unsubscribeOnError: true;
+    );
+    return result;
   }
 
   /** Reduces a sequence of values by repeatedly applying [combine]. */
@@ -272,7 +295,7 @@ abstract class Stream<T> {
       (/*T*/ element) {
         _runUserCode(
           () => combine(value, element),
-          (result) { value = result; },
+          (newValue) { value = newValue; },
           _cancelAndError(subscription, result)
         );
       },
@@ -414,98 +437,6 @@ abstract class Stream<T> {
     return future;
   }
 
-  /**
-   * Finds the least element in the stream.
-   *
-   * If the stream is empty, the result is [:null:].
-   * Otherwise the result is a value from the stream that is not greater
-   * than any other value from the stream (according to [compare], which must
-   * be a [Comparator]).
-   *
-   * If [compare] is omitted, it defaults to [Comparable.compare].
-   *
-   * *Deprecated*. Use [reduce] with a binary min method if needed.
-   */
-  Future<T> min([int compare(T a, T b)]) {
-    if (compare == null) {
-      var defaultCompare = Comparable.compare;
-      compare = defaultCompare;
-    }
-    _FutureImpl<T> future = new _FutureImpl<T>();
-    StreamSubscription subscription;
-    T min = null;
-    subscription = this.listen(
-      // TODO(ahe): Restore type when feature is implemented in dart2js
-      // checked mode. http://dartbug.com/7733
-      (/*T*/ value) {
-        min = value;
-        subscription.onData((T value) {
-          _runUserCode(
-            () => compare(min, value) > 0,
-            (bool foundSmaller) {
-              if (foundSmaller) {
-                min = value;
-              }
-            },
-            _cancelAndError(subscription, future)
-          );
-        });
-      },
-      onError: future._setError,
-      onDone: () {
-        future._setValue(min);
-      },
-      unsubscribeOnError: true
-    );
-    return future;
-  }
-
-  /**
-   * Finds the largest element in the stream.
-   *
-   * If the stream is empty, the result is [:null:].
-   * Otherwise the result is an value from the stream that is not smaller
-   * than any other value from the stream (according to [compare], which must
-   * be a [Comparator]).
-   *
-   * If [compare] is omitted, it defaults to [Comparable.compare].
-   *
-   * *Deprecated*. Use [reduce] with a binary max method if needed.
-   */
-  Future<T> max([int compare(T a, T b)]) {
-    if (compare == null)  {
-      var defaultCompare = Comparable.compare;
-      compare = defaultCompare;
-    }
-    _FutureImpl<T> future = new _FutureImpl<T>();
-    StreamSubscription subscription;
-    T max = null;
-    subscription = this.listen(
-      // TODO(ahe): Restore type when feature is implemented in dart2js
-      // checked mode. http://dartbug.com/7733
-      (/*T*/ value) {
-        max = value;
-        subscription.onData((T value) {
-          _runUserCode(
-            () => compare(max, value) < 0,
-            (bool foundGreater) {
-              if (foundGreater) {
-                max = value;
-              }
-            },
-            _cancelAndError(subscription, future)
-          );
-        });
-      },
-      onError: future._setError,
-      onDone: () {
-        future._setValue(max);
-      },
-      unsubscribeOnError: true
-    );
-    return future;
-  }
-
   /** Reports whether this stream contains any elements. */
   Future<bool> get isEmpty {
     _FutureImpl<bool> future = new _FutureImpl<bool>();