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Iterating NSSet (was Re: My new framwork)

On Mar 3, 2004, at 2:09 PM, Allan Odgaard wrote:

This seems straightforward enough:
Forwards:
unsigned currentIndex = [indexSet firstIndex];
while (currentIndex != NSNotFound)
{
//...
currentIndex = [indexSet indexGreaterThanIndex:currentIndex];
}
I should have added efficiently. I doubt that indexGreaterThanIndex: is O(1) and thus a bad idea for iterating large index sets, which is also hinted by the documentation for getIndexes:maxCount:inIndexRange:, which says: "Use this method to quickly and efficiently traverse an index set".

NSIndexSet internally caches last-accesses, allowing such enumeration (forwards or backwards) to happen very efficiently. The code snippet above should be good enough for most uses. A reason to switch to the get... variant is to avoid the message-sending overhead of the loop, in case that becomes an issue.

mmalc
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References: 
 >My new framwork (From: April Gendill <email@hidden>)
 >Re: My new framwork (From: John Randolph <email@hidden>)
 >Re: My new framwork (From: Allan Odgaard <email@hidden>)
 >Re: My new framwork (From: mmalcolm crawford <email@hidden>)
 >Re: My new framwork (From: Allan Odgaard <email@hidden>)



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