ListXnotY

Function: list ListXnotY(list lx, list ly);

Show what x list has that y list is missing.

See also: Lists

<lsl> list ListXnotY(list lx, list ly) {// return elements in X list that are not in Y list

   list lz = [];
   integer i = 0;
   integer n = lx != []; list t;
   for (; i < n; i++) 
       if (!~llListFindList(ly, (t = llList2List(lx, i, i)))) lz += t; //Note *
   return lz;

}

</lsl> Note: If the if test is written as if (!~llListFindList ... , the result will be a list of items in X that are missing from list Y. If it is written as if (~llListFindList ... , the result will be a list in X that are present in list Y.

Example:

<lsl> list l1 = ["a","b","c","d"]; list l2 = ["a","1","b","2","c","3"];

list ListXnotY(list lx, list ly) {// return elements in X list that are not in Y list

   list lz = [];
   integer i = 0;
   integer n = llGetListLength(lx);
   for (; i < n; i++)
       if (llListFindList(ly,llList2List(lx,i,i)) == -1)
           lz += llList2List(lx,i,i);
   return lz;

}

default{

  state_entry() {
     llSay(0, "X list has this in it, but Y list doesn't: " + llList2CSV(ListXnotY(l1,l2)) );
     //will say: d
  }

} </lsl>

Posted with the kind permission of Very Keynes, who originated this script June 2007 in the SL scripters forum http://forums-archive.secondlife.com/54/e4/194138/1.html