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Removing (or picking) items from list 1 via list 2?
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Removing (or picking) items from list 1 via list 2?


  • Subject: Removing (or picking) items from list 1 via list 2?
  • From: Charles Arthur <email@hidden>
  • Date: Tue, 23 Apr 2002 18:06:38 +0100

Hi.

Here's the problem, speed freaks.
I have a list - list1 - which could get quite large - say, 400-500 items,
all OS aliases.
Meanwhile I also have list2 which will also have lots of aliases. Might
easily be bigger than list1.
I want to pick things randomly from list1 that aren't in list2, to create
mywanteditem.

I had thought of
--
set found to false
repeat until found is true
set randomnum to (random number from 1 to count items in list1)
if item randomnum of list1 is not in list2 then
set mywanteditem to item randomnum of list1
set found to true
end repeat
mywanteditem
--

But I wonder if the fastest way eventually might be
Is the best way to create list3, by eg
--
set list3 to {}
set list3ref to a reference to list3
repeat with anitem in list1
if anitem is not in list2 then set end of list3ref to anitem
end repeat
set randomnum to randomnumber from 1 to count items in list3
set mywanteditem to item randomnum of list3
--

?
Which is the more efficient way? Or is there an even more efficient method?
This is all in the context of a big repeat loop where the contents of list1
will keep changing (it'll be created afresh, but get smaller, with each
loop).

Also: using OSX, vanilla because I want to include it in some code I'll be
distributing.

Charles

----------------------------
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