filter?

[Pete]

Now I can add "symmetric difference" to my extremely small vocabulary of set
theory terms! Largely academic at this point but there is a variation to the
array solution that Jacque and I offered which does it all in one repeat
loop:

put tlist1 & cr & tlist2 into tlist3
repeat with x=1 to the number of lines in tlist3
  if  line x of tlist3 is among the keys of tarray then
    delete variable tarray[line x of tlist3]
  else
    put true into tarray[line x of tlist3]
  end if
end repeat

At the end of the repeat, the keys of tarray will be the unique values.  I
have no idea if substituting the if statement for an extra repeat loop makes
it more efficient.

Pete
Molly's Revenge <http://www.mollysrevenge.com>




On Thu, Jun 23, 2011 at 3:40 AM, Dick Kriesel <dick.kriesel at mail.com> wrote:

>
> On Jun 22, 2011, at 10:58 PM, Pete wrote:
>
> > I may be wrong, but I don't think intersect solves the problem.  If I
> > understand the dictionary correctly, this will remove all the t1 keys
> that
> > do NOT match t2 keys so it does the opposite of what is needed.
>
> Thanks, Pete. I misunderstood the OP.
>
> He wants the symmetric difference.
>    <http://en.wikipedia.org/wiki/Symmetric_difference>
>
> Here's a way:
>
>
> function symmetricDifferenceOfLists t1, t2
>   split t1 by cr and tab
>   split t2 by cr and tab
>   return the keys of symmeticDifferenceOfArrays( t1, t2 )
> end symmetricDifferenceOfLists
>
> function symmeticDifferenceOfArrays p1, p2
>   local tResult
>   put differenceOfArrays( p1, p2 ) into tResult
>   union tResult with differenceOfArrays( p2, p1 )
>   return tResult
> end symmeticDifferenceOfArrays
>
> function differenceOfArrays t1, p1
>   repeat for each key tKey in p1
>      delete variable t1[ tKey ]
>   end repeat
>   return t1
> end differenceOfArrays
>
>
> In comparison, Jacque's code is looking lean.
>
> -- Dick
>
>
>
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