# ListXnotY

 LSL Portal

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

Show what x list has that y list is missing.

```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