On May 23, 2008, at 3:49 PM, Sherm Pendley wrote:
The implementation of foreach appears almost expressly designed to
better
support scripting languages. The ObjC foreach() syntax is just
chrome - the
"fast" comes from under the hood. It compiles down to a single
method that's
called to get a count of items and a C array of ids. For a scripting
bridge,
an opportunity to replace several trips across the bridge per
iteration with
a single round trip for the whole array is *huge*.
That for(... in ...) supports more efficient bridging is a benefit of
the design, but not the initial goal.
The motivation for the feature was two fold:
(1) Increase developer productive by Eliminating all of the repetitive
uses of object enumerators (of NSEnumerator) with something far more
compact and readable. The NSEnumerator stuff is prone to introducing
silly errors, is inefficient, and not very pleasant to look at.
(2) Vastly improve enumeration performance of both Apple provided and
developer written code by offering an API that could be leveraged to
provide for(... in ...) compatible enumeration that is very very
fast. As you note, the design is very much focused on making it
possible to enumerate large sets of foreign data -- potentially
infinite in size -- efficiently.
b.bum
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