val modBalance : balance -> unit
val deleteBalance : int -> unit
val listBalances : unit -> balance list
val modBalance : balance -> unit
val deleteBalance : int -> unit
val listBalances : unit -> balance list
val listBalanceUsers : int -> Init.user list
val validBalanceName : string -> bool
val balanceNameToId : string -> int option
val listBalanceUsers : int -> Init.user list
val validBalanceName : string -> bool
val balanceNameToId : string -> int option