let comparisons _info f e1 e2 =
try
let k1,v1 = find_lonely_key e1 in
let k2,v2 = find_lonely_key e2 in
if Base.compare k1 k2 <> 0
then zero_or_one
else Ival.compare_C f v1 v2
with Not_found ->
zero_or_one