Refactor List.setRange function.

sdk/lib/core/list.dart

Index: sdk/lib/core/list.dart
diff --git a/sdk/lib/core/list.dart b/sdk/lib/core/list.dart
index 27a857e9df442afb0bc957bb4f861fe10537009b..470d8ce80171fd92ca0cfbf07b14d5cea7177ff5 100644
--- a/sdk/lib/core/list.dart
+++ b/sdk/lib/core/list.dart
@@ -263,15 +263,19 @@ abstract class List<E> implements Iterable<E> {
   Iterable<E> getRange(int start, int end);
 
   /**
-   * Copies [length] elements of [from], starting
-   * at [startFrom], into the list, starting at [start].
-   * If [length] is 0, this method does not do anything.
-   * Throws an [ArgumentError] if [length] is negative.
-   * Throws an [RangeError] if [start] or
-   * [:start + length - 1:] are out of range for [:this:], or if
-   * [startFrom] or [:startFrom + length - 1:] are out of range for [from].
+   * Copies the elements of [iterable], skipping the [skipCount] first elements

[Anders Johnsen, 2013/04/15 09:24:04]

first elements,

[floitsch, 2013/04/15 13:45:34]

Done.

+   * into the range [start] - [end] of `this`.
+   *
+   * If [start] equals [end] and represent a legal range, this method has
+   * no effect.
+   *
+   * It is an error if [start]..[end] is not a valid range pointing into the
+   * `this`.
+   *
+   * It is an error if the [iterable] does not have enough elements after
+   * skipping [skipCount] elements.

[Anders Johnsen, 2013/04/15 09:24:04]

Will it throw when at end, or before it starts copying?

[Lasse Reichstein Nielsen, 2013/04/15 10:16:10]

It must be able to throw at the end, because there is no other way to know that
it doesn't have enough elements in the general case.
So it might as well just throw there in all cases.

Which means that it's possible to use this function to write "as many elements
as in X" at position "i" by doing:
  try {
    foo.setRange(i, foo.length, X)
  } catch (e) {}
We do not want to make this the only way to get that functionality. That is why
I prefer:
  List.setFromIterable(int at, Iterable source)
or even 
  List.setRange(int at, Iterable source, [int start = 0, int end])
but you can do that with skip/take on the iterable.

This signature is counter productive and confusing (but I think I already
mentioned that in another CL). The "end" is not related to anything here. It is
the wrong place to put the limit, because it might not match the length of the
iterable, so it would make it more direct to put it as a limit on the iterable
instead. And accept shorter iterables.

    */
-  void setRange(int start, int length, List<E> from, [int startFrom]);
+  void setRange(int start, int end, Iterable<E> iterable, [int skipCount = 0]);

[Lasse Reichstein Nielsen, 2013/04/15 10:16:10]

If this is working on an Iterable, and not the efficient sublist-copy function,
I don't mind dropping the "skipCount" parameter. You can always use skip on the
iterable.

I still don't like the "start, end of this" way of making a requirement on
"iterable". Put the limits on iterable directly.

[floitsch, 2013/04/15 13:45:34]

This is the efficient method. Keeping 'skipCount'.

 
   /**
    * Removes [length] elements from the list, beginning at [start].