`type xinstr =`

1. `| Instr of instr * loc`
2. `| Last of last * loc`

`val expr : Stdlib.Format.formatter -> expr -> unit`
`val constant : Stdlib.Format.formatter -> constant -> unit`
`val var_list : Stdlib.Format.formatter -> Var.t list -> unit`
`val instr : Stdlib.Format.formatter -> (instr * loc) -> unit`
`val block : (Addr.Map.key -> xinstr -> string) -> int -> block -> unit`
`val program : (Addr.Map.key -> xinstr -> string) -> program -> unit`
`val last : Stdlib.Format.formatter -> (last * loc) -> unit`
`val cont : Stdlib.Format.formatter -> cont -> unit`