On Wed, Sep 28, 2011 at 10:06 PM, Mike Shaver <[email protected]> wrote:
> On Wed, Sep 28, 2011 at 9:11 PM, Brendan Eich <[email protected]> wrote: > > No worries, array extras are a great addition, we just need to keep > rolling. > > Oh, no offense taken. I just meant to say that there may be > consistency-with-existing-pattern reasons to prefer one hole behaviour > over another, is all. > Another reason to prefer the current hole-hopping behavior for array extras is that it's currently the *only* way to get any efficiency advantage sparse arrays. So regardless of rationale, it's strictly more featureful and almost certainly the intended behavior if, as a developer, you're aware of holes. But to reiterate the point I made earlier, in order for libraries to take complete ownership of looping constructs we need a better way to detect holes in userland -- something that can be optimized. I was trying to think of a way to overload Array.prototype.indexOf and lastIndexOf but since we don't have a type for holes this isn't really feasible (I'd thought of using NaN as a sigil here as it's otherwise untestable in indexOf, but this would be wrong on so many levels). Regardless of where it goes (on Array, Array.prototype, or in a system module), all we really need is something like a function that takes an index and direction and returns the next hole's start index and length (or end index). I'll put together a proposal if this isn't too controversial.
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