How to get the difference between two lists?

[Dar Scott]

On Apr 3, 2005, at 9:04 PM, Ken Ray wrote:

> I can of course do a repeat loop through the small list and remove 
> those
> items from the comprehensive list, but I'm wondering if there's a 
> faster way
> to do this.

I took a break and tried my hand at this.

The function using offset did better than array element deletion in 
some cases.  The function using replaceText() did poorly for medium 
size lists and bailed out for large lists to be removed.  I think there 
is something fishy (that is n^2) in replaceText().  The last one was my 
attempt to avoid 'line n' and is similar to Frank's, I think.  It was 
still a little bit slower than array element deletion in my tests.

function shortListDar2 pList, pExcludeList
   local resultList = ""
   put lf before pList
   put 0 into lastUsedChar
   if char -1 of pList is not lf then put lf after pList
   repeat for each line ex in pExcludeList
     put lf & ex & lf into exWithLF
     get offset(exWithLf,pList,lastUsedChar)
     if it is not zero then
       put char lastUsedChar+1 to lastUsedChar+it of pList after 
resultList
       put lastUsedChar + it + length(exWithLF) - 1 into lastUsedChar
     end if
   end repeat
   put char lastUsedChar+1 to -1 of pList after resultList
   return char 2 to -2 of resultList
end shortListDar2

--function shortListDar3 pList, pExcludeList
--  get "(?m)^" & replaceText(pExcludeList,"\n","\n|^") & "\n"
--  return replaceText(pList,it,empty)
--end shortListDar3

function shortListDar4 pList, pExcludeList
   local resultList
   put lf & "10000000000000" after pExcludeList
   put line 1 of pExcludeList into checkLine
   put 1 into charOffset
   repeat for each line listLine in pList
     repeat while checkLine < listLine
       add length(checkLine)+1 to charOffset
       put line 1 of (char charoffset to charoffset+20 of pExcludeList) 
into checkLine
     end repeat
     if listLine < checkline then
       put listLine & lf after resultList
     end if
   end repeat
   return char 1 to -2 of resultList
end shortListDar4
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