Efficiency question for list modification

[dunbarx at aol.com]

I ran this with a field "rawData" containing 5000 lines:



on mouseUp
   put  the ticks into aa
   put  fld "rawdata" into temp
   put 3 into div1
   put 5 into div2
   repeat with y = 1 to the number of lines of temp
      put item 1 of line y of temp / div1 & "," & item 2 of line y of temp / div2 into line y of temp
   end repeat
   put temp into fld "tresult"
   put the ticks - aa
end mouseUp


Took about 2.5 seconds. 


If that is too slow, what if you added a third item for each of the lines in your data field, such that the lines were numbered:


If you had:


3,6
4,7
5,8


Make it into:


1,3,6
2,4,7
3,5,8


Now you can use an array, and the ordering can be recovered since the lines contain unique identifiers.


Craig Newman



-----Original Message-----
From: FlexibleLearning <admin at FlexibleLearning.com>
To: use-livecode at lists.runrev.com
Sent: Thu, Mar 10, 2011 1:51 pm
Subject: Efficiency question for list modification


Problem:
I have a long list of several thousand lines.
Each line contains two comma-separated numbers.
I want to divide the first item of each line by one divisor, and divide the
second item of each line by a different divisor.
The list order must stay the same.

Example:
Using 2 and 5 as divisors...
  10,10
  12,15
  8,12
would become
  5,2
  6,3
  4,2.4

Options:
Using "repeat with n=1 to num of lines" takes far too long.
Using "repeat for each line L" either attempts to modify read-only data, or
is only 25% faster using a dumping variable.
Using split/combine will mess up the ordering (numeric array keys are not
sorted numerically with combine).

Any other ideas?

Hugh Senior
FLCo





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