let ensure_integer e1 =
match (type_of e1).ct_ty with
Tbuiltin
(Tchar | Tschar | Tuchar
| Tshort | Tushort
| Tint | Tuint
| Tlong | Tulong
| Tlonglong | Tulonglong) -> ()
| _ -> raise (TypeError_typed(e1,"not an integer"))