ListXnotY

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

Show what x list has that y list is missing.

See also: Lists

list ListXnotY(list lx, list ly) {// return elements in X list that are not in Y list
    list lz;
    integer i = llGetListLength(lx);
    while(i--)
	if ( !~llListFindList(ly,llList2List(lx,i,i)) )  // * see Note
            lz += llList2List(lx,i,i);
    return lz;
}

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

Example:

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 = llGetListLength(lx);
    while(i--)
	if ( !~llListFindList(ly,llList2List(lx,i,i)) )
            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
   }
}
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