Added MappedListIterable/Iterator to implement map() on Lists.

Added MappedListIterable/Iterator to implement map() on Lists.

Committed: https://code.google.com/p/dart/source/detail?r=18036

[floitsch, 2013-02-01 15:00:36]

LGTM.
can't the MappedList not share some of the functionality?

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
File sdk/lib/collection_dev/iterable.dart (right):

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
sdk/lib/collection_dev/iterable.dart:143: for (int i = _startIndex, n =
_endIndex; i < n; i++) {
for another CL: in theory we could say min(_endIndex, _list.length)
If it's written correctly it should help the VM.

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/list.dart
File sdk/lib/collection_dev/list.dart (right):

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/list.d...
sdk/lib/collection_dev/list.dart:10: class IterableView<E> extends Iterable<E> {
Is this class used?

[Lasse Reichstein Nielsen, 2013-02-01 15:13:57]

Sadly we can't reuse MappedList code. It's based on the Iterable *being* a List
(having length and operator[]) and we don't want that for this Iterable.

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
File sdk/lib/collection_dev/iterable.dart (right):

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
sdk/lib/collection_dev/iterable.dart:143: for (int i = _startIndex, n =
_endIndex; i < n; i++) {
The problem is that min is in dart:math, and I don't want to import that just
for two "min" calls.

It should really be on num in some way, even if only index.restrictToRange(0,
_list.length)

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/list.dart
File sdk/lib/collection_dev/list.dart (right):

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/list.d...
sdk/lib/collection_dev/list.dart:10: class IterableView<E> extends Iterable<E> {
Whoops, no. Didn't need it anyway, and forgot to remove it.
Will remove.

[floitsch, 2013-02-01 15:23:39]

There must be ways to share code, but let's do this at another time.

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
File sdk/lib/collection_dev/iterable.dart (right):

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
sdk/lib/collection_dev/iterable.dart:143: for (int i = _startIndex, n =
_endIndex; i < n; i++) {
On 2013/02/01 15:13:57, Lasse Reichstein Nielsen wrote:
> The problem is that min is in dart:math, and I don't want to import that just
> for two "min" calls.
> 
> It should really be on num in some way, even if only index.restrictToRange(0,
> _list.length)
> 

the "min" was just to illustrate. It should be something like:
int length = _list.length;
int endIndex = _endIndex;
if (length < endIndex) endIndex = length;

something like this. Ideally in a way that the VM can propagate.

[Lasse Reichstein Nielsen, 2013-02-04 09:30:16]

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
File sdk/lib/collection_dev/iterable.dart (right):

https://codereview.chromium.org/12094103/diff/1/sdk/lib/collection_dev/iterab...
sdk/lib/collection_dev/iterable.dart:143: for (int i = _startIndex, n =
_endIndex; i < n; i++) {
If we can see a difference in performance after profiling, I'm willing to
rewrite _endIndex. Or wait for the VM to get better at analyzing.