support ES6 iterators

[haberman]

The ES6 iterator protocol is a bit different than what js_bintrees implements. Any chance js_bintrees could add support for this?

This would allow code like this in ES6:

function logRBTree(tree) {
  for (item of tree.iterator()) {
    console.log(item);
  }
}

Unfortunately this would be a backward-incompatible change. The only two ideas that spring to mind are:

1. having some global setting for which iterator style you vend.
2. having two sets of methods (ie. tree.es6Iterator(), tree.es6FindIter(), etc).

Thanks for writing js_bintrees!

[haberman]

(btw, I'm not actually using ES6 yet, but I'm writing an iterator-heavy app and trying to standardize on ES6 style. For now I'll just write wrappers around RBTree.)

[vadimg]

Yeah, the backwards-incompatibility of ES6 iterators with mine is a bit unfortunate. I'll have to think for a bit about how to best solve this. For now, it's not really an issue because ES6 hasn't even been standardized yet. Thanks for the heads up, though!

[sbking]

It's a bit of an annoyance because many engines already support iterators/generators and many ES6 features can be compiled to ES5, but generators allow a simple solution that works well enough:

function* iterateTree(tree) {
  let it=tree.iterator(), item;
  while((item = it.next()) !== null) {
    yield item;
  }
}

for (let item of iterateTree(tree)) {
  // do stuff with item
}

[haberman]

Just wanted to mention that ES6 is complete now, with a standardized iterator interface!

[vadimg]

Ok, here's the plan:

• Bump up the version to 2.0.0
• By default, iterator() will work the ES6 way
• There will be a global compatibility flag you can set to make iterator() work the old way. This flag will have an option:
  • By default, it will print a compatibility warning to console.log whenever iterator() is called. This way you can make sure that you have changed all instances of iterator() to reversibleIterator() before you disable compatibility mode.
  • If you don't care to ever update your code, you can disable this warning.
• If you want to use the old iterator, it will be available as reversibleIterator()

What do you guys think?

[haberman]

What about findIter(), lowerBound(), and upperBound()? Would there be two versions of those methods?

I do see the value of having old-style iterators also, because they are more flexible. A single old-style iterator can go forwards or backwards or even switch in the middle of iteration.