signature BALANCE =
sig
- type balance = {id :int, name : string, amount : real}
+ type balance = {id : int, name : string, amount : real}
val addBalance : string -> int
val lookupBalance : int -> balance
val balanceNameToId : string -> int option
val sumOwnedBalances : unit -> real
+ val isNegative : balance -> bool
+
+ val depositAmount : int -> real
end