On Monday, 20 May 2019 at 12:50:29 UTC, Simen Kjærås wrote:
There are some caveats when using doubles, as floating-point math is not always equal to regular math. For instance, if you had the entire world economy in one variable, you could subtract a cent at a time without the variable decreasing. If these cents were simultaneously added to a different variable (to represent a transaction), this would be an infinite source of money.
Yes, but it is fine until 2^53 which is the number 9007199254740992. So better than 31 bit ints and only slightly worse than 63 bit (signed).
Doubles behave like like integers from 0 up to 2^53 for addition, so if you do cents in double then you also get accurate representation of cents while also getting decent fractional representation when converting to another currency.
If it is important for the game to not leak resources then I guess you would have to recalibrate the system from time to time. It might be hard to find where money leak. Integers have the same problem, however.
If it is a game, you might want to use the same storage-type and system for all countable resources, though. Then you could do something more advanced and memory efficient, either one storage object per owner, or as a global database object.
So if you have lots of (unlimited) resource-pools (accounts, bottles, containers etc) to track you could to create your own "bank" or "wallet" as an in-memory database which uses variable length data records with encapsulated memory management on a local heap. So if you have 200 units it uses 1 byte more than an empty account, if you have a billion units it uses 4 bytes, a trillion units uses 5 bytes, 1000 trillion units use 7 bytes more…
One advantage of using a "bank" is that you can ensure that resources don't leak as you have to set up a "transaction" between "accounts". (the same amount of money/resources are both added or removed at single point). Less error-prone.
If it is a simulation game then it would also be easier to create logs that are useful for debugging/balancing if you have a mandatory "transaction" concept (you get a single point where all a transactions have to pass, and there you can log it).
Anyway, lots of options. Have fun!
