Wouter,
I'm not sure what this example has to do with the question on the
thread, but you first example is a speed killer. Putting things in
front of a string causes the whole string to be shuffled to make room
for the inserted string. It is a worst case situation --although I
can always come up with a way to make it slower. It would be faster
to use the slower repeat for i=number of lines in x down to 1 and
then put the lines after like your second example.
Splitting into an array is usually a good approach if the repeat for
each construct will not work. However, it does take time to do the
split. A repeat for each could process the whole string in less time
than it takes to split it if a repeat for each fits the problem.
In your second example, sorting the keys will also take time. You
might be better off with just a simple repeat for i=number of lines
in x down to 1 as the array index. You would have to try it on your
array to see.
Dennis
On Jun 27, 2005, at 4:24 PM, Wouter wrote:
Hi,
Using the following to reverse the order of lines of a field
containing 525605 chars in 14194 lines
reversing by:
on mouseUp
put fld 1 into x
put the long seconds into zap
repeat for each line i in x
put i&cr before tList
end repeat
put the long seconds - zap
put tList into fld 1
end mouseUp
takes > 60 seconds on a slowbook (G4 400 mhz)
reversing by:
on mouseUp
put fld 1 into x
put the long seconds into zap
split x by return
get the keys of x
sort it numeric descending
repeat for each line i in it
put x[i]&cr after tList
end repeat
put the long seconds - zap
put tList into fld 1
end mouseUp
yields around 0.413007 seconds on a slowbook (G4 400 mhz)
(which is not too bad)
The amount of chars and lines has a big influence on the speed in
the first handler,
while in the second handler it has not.
Greetings,
Wouter
On 27 Jun 2005, at 14:40, Dennis Brown wrote:
The repeat for each only goes in forward sequential order starting
at the beginning, except for arrays where the order is indeterminate.
I have requested a sequential access enhancement to allow for
constructing this type of looping in a more flexible way (like
parallel instantiation, starting at an arbitrary point, and
reverse order), to make it possible to wander all over your data
sequentially with the speed of the repeat for each method.
However, it would be most useful with some improved string
delimiter handling. Bugzilla # 2773
Having a reverse order repeat for each might be up to twice as
slow as the forward version depending on how it is implemented,
because it has to go backwards to the previous delimiter then
forward to pick up the data, though it could pick up the data in
reverse order on the way back. However, even twice as slow would
be much faster than any other method.
Dennis
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