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Re: [Public WebGL] typed arrays + edge cases

On Feb 3, 2010, at 9:41 PM, Vladimir Vukicevic wrote:

> On 2/3/2010 7:04 PM, Chris Marrin wrote:
>> On Feb 3, 2010, at 2:50 PM, Vladimir Vukicevic wrote:
>>> A few edge cases keep coming up that are underspecified currently... a few of these we talked about in the past, but I don't know if we captured
>>> - If a non-numeric array property is set/read, what happens?
>>> Suggestion: exception (we have out-of-bounds numeric indexes spec'd to raise an exception currently, so this falls in the same category to me)
>> I'd really like this to work. It enables using arrays to store additional, application specific data, just like normal Arrays.
> Mm.. I'd actually like to discourage this since it makes it much harder to reason about these objects.  It's a pretty big win for perf (at least for us) if it's possible to say "property access on this object will always return type X or will throw an exception".  For storing additional properties, I think that { data: Uint8Array(...), otherProp: false, someOtherProp: true } is just as easy, and not allowing them on the typed arrays really reinforces that it's not a generic object, and I don't think they should be treated as such.

i don't buy this at all -- they _are_ an object -- in a js binding typeof will produce "object".... I suppose it would be conceivable that we could make the object inextensible (per es5 semantics) but i don't really see what that buys us, CanvasPixelArray in webkit is internally implemented as a ByteArray but is still an object and can be treated as such, and I don't see anything that making it inextensible would give us that could improve performance...


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