Yes and no. Sorry to repeat the point, but you 
put the blame in the wrong place again
in talking of the inefficiency of -while-, 
which is just a framework and not to blame 
for what's inside. 
The ineffiency of -while- is in going (e.g.)
local i = 1 
while `i' < 1000 { 
	...
	local i = `i' + 1 
} 
rather than (say) 
forval i = 1/1000 { 
	...
}
-- although note that not every -while- 
can be made a -forval- --
but that's small beer compared with the 
possible inefficiency of what the user 
puts within the loop, which is the issue here. 
Nick 
[email protected] 
Subhankar Nayak
> 
> Yes, that's a very interesting point that I had missed.
> I now see why -while- is so inefficient: it reads such a huge 
> fraction of
> unneccesary observations. I can avoid that by more efficient 
> treatment of
> the observation: avoid reading all those unneccesary observations
> repeatedly.
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