On 2015-02-16 22:02, Mike Kerner wrote:
I don't think I follow on the first part. Edinburgh says that the
complexity of the two traversals are dramatically different. repeat
for
each is somewhere between nlogn and n, and repeat with is n^2. At
least
for the case of your squares of integers, I would expect that there is
a
crossover where it's going to be faster to build the list, first. I
don't
know if that is at 100, 1000, or some bigger number, but n vs. n^2 is a
very big difference.
You are mistakenly fixating on the "repeat" syntax. The cost of the
"repeat with..." form of your loop over lines isn't in the actual repeat
syntax -- it's what comes before it and what's in the loop body.
put the number of lines in tData into N -- This chunk op is O(N)
repeat with i = 1 to N -- This is very very cheap
put line i of tData into tLine -- This chunk op is O(N) and
occurs N times
-- Operate on tLine
end repeat
Compare with your "printing the squares of integers" example:
repeat with i = 1 to 100 -- This is very very cheap
put i*i -- This is O(1) and occurs N times
end repeat
The cost is *not* in the repeat form. The cost is in the chunking
operations. The "repeat for each..." form of your loop is faster
because it requires fewer chunking operations.
Peter
--
Dr Peter Brett <peter.br...@livecode.com>
LiveCode Engine Development Team
_______________________________________________
use-livecode mailing list
use-livecode@lists.runrev.com
Please visit this url to subscribe, unsubscribe and manage your subscription
preferences:
http://lists.runrev.com/mailman/listinfo/use-livecode
