let compare kf1 kf2 =
if kf1 == kf2 then 0
else
let res =
String.compare
(Kernel_function.get_name kf1)
(Kernel_function.get_name kf2)
in
if res <> 0 then res
else
String.compare
(Kernel_function.get_vi kf1).vname
(Kernel_function.get_vi kf2).vname