Added full js & js_util packages

packages/quiver_iterables/lib/src/range.dart

+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// 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.
+
+part of quiver.iterables;
+
+/// Returns an [Iterable] sequence of [num]s.
+///
+/// If only one argument is provided, [start_or_stop] is the upper bound for the
+/// sequence. If two or more arguments are provided, [stop] is the upper bound.
+///
+/// The sequence starts at 0 if one argument is provided, or [start_or_stop] if
+/// two or more arguments are provided. The sequence increments by 1, or [step]
+/// if provided. [step] can be negative, in which case the sequence counts down
+/// from the starting point and [stop] must be less than the starting point so
+/// that it becomes the lower bound.
+Iterable<num> range(num start_or_stop, [num stop, num step]) {
+  var start = (stop == null) ? 0 : start_or_stop;
+  stop = (stop == null) ? start_or_stop : stop;
+  step = (step == null) ? 1 : step;
+  if (step == 0) {
+    throw new ArgumentError("step cannot be 0");
+  }
+  if ((step > 0) && (stop < start)) {
+    throw new ArgumentError("if step is positive,"
+        " stop must be greater than start");
+  }
+  if ((step < 0) && (stop > start)) {
+    throw new ArgumentError("if step is negative,"
+        " stop must be less than start");
+  }
+  return _range(start, stop, step);
+}
+
+Iterable<num> _range(num start, num stop, num step) sync* {
+  while (step < 0 ? start > stop : start < stop) {
+    yield start;
+    start += step;
+  }
+}