ETuple val = (ETuple) vals.head();
key = val.elm(keypos1);
IPersistentCollection coll = (IPersistentCollection) map.valAt(key);
if (coll instanceof IPersistentSet) {
IPersistentSet set = (IPersistentSet) coll;
set = set.disjoin(val);
if (set != coll) {
count += 1;
if (set.count() == 0) {
map = map.without(key);
} else {
map = map.assoc(key, set);
}
}