declare
fun {From C1 C2 C3}
   c(methods:M1 attrs:A1)={Unwrap C1}
   c(methods:M2 attrs:A2)={Unwrap C2}
   c(methods:M3 attrs:A3)={Unwrap C3}
   MA1={Arity M1}
   MA2={Arity M2}
   MA3={Arity M3}
   ConfMeth={Minus {Inter MA2 MA3} MA1}
   ConfAttr={Minus {Inter A1 A2} A3}
in
   if ConfMeth\=nil then
      raise illegalInheritance(methConf:ConfMeth) end
   end
   if ConfAttr\=nil then
      raise illegalInheritance(attrConf:ConfAttr) end
   end
   {Wrap c(methods:{Adjoin {Adjoin M2 M3} M1}
           attrs:{Union {Union A2 A3} A1})}
end