| // 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]) => |
| new _Range(start_or_stop, stop, step); |
| |
| class _Range extends IterableBase<num> { |
| final num start, stop, step; |
| |
| _Range(num start_or_stop, num _stop, num _step) |
| : 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"); |
| } |
| } |
| |
| Iterator<num> get iterator => new _RangeIterator(start, stop, step); |
| } |
| |
| class _RangeIterator implements Iterator<num> { |
| final num _stop, _step; |
| num _value; |
| bool _hasNext; |
| bool _inRange; |
| |
| _RangeIterator(num start, num stop, this._step) |
| : _value = start, |
| _stop = stop, |
| _hasNext = true, |
| _inRange = false; |
| |
| num get current => _inRange ? _value : null; |
| |
| bool moveNext() { |
| if (_hasNext && _inRange) _value += _step; |
| _inRange = _hasNext = (_step > 0) ? (_value < _stop) : (_value > _stop); |
| return _hasNext; |
| } |
| } |