On Tue, Jun 11, 2013 at 4:34 AM, Andy Wingo <[email protected]> wrote:
> So, my proposal would be to make the for-of RHS expect an iterator, and > remove the concept of "iterable". So there's no need to check for > anything; you just assume you have an iterator. > > I don't find the cost of this change (let's not say "tax" ;) terrible: > > for (x of y.values()) f(x); > I can see the tradeoffs between a tax on the performance of loops and a tax on people who want to implement iterators without using generators (hint: use a generator). But a tax on everyone who wants to write a loop seems clearly much worse. As iterators and for-of become more prevelant, I think there are > actually few times that you want the default iterator -- the reason > being that you will deal more with iterators and less with reified > containers like arrays. The evolution of Python seems to show this, and > (dare I mention it?) Dart also seems to be going in this direction. > I can't speak for Dart, but the evolution of Python shows no such thing. Please look at any Python codebase. The right-hand side of a for loop is most often just an identifier or simple expression naming a collection. You will see a few calls to enumerate(), .items(), and so on, but they do not predominate. Sometimes it's a list literal. I will quantify this later today. -j
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