int nprims = nprimitives(0);
string curValue; //aka current value used
string allValues[];
// simply placing all values in an array
for(int i=0; i<nprims; i++)
    {
    curValue = prim(0, "subset", i);
    push(allValues, curValue);
    }
sort(allValues); //a long array containing lots of duplicates but all sorted

// cleaning (removing duplicates)
string storedValue = allValues[0]; //storing first value
string cleanedValues[];
push(cleanedValues, allValues[0]); //I need one value to begin

for(int i=0; i<nprims; i++)
    {
    curValue = prim(0, "subset", i);
    if(storedValue != curValue)
        {
        push(cleanedValues, curValue);
        storedValue = curValue;
        }
    }

string attrib = "subset";
int count = nuniqueval(0, "prim", attrib);
for (int i=0; i<count; i++){
    string value = uniqueval(0, "prim", attrib, i);
    append(s[]@unique, value);
}

string attrib = "subset";
s[]@unique = uniquevals(0, "prim", attrib);