[//]: # () A simple-interest yielding bank account in Leo. ## Summary This program implements a bank that issues tokens to users and allows users to deposit tokens to accrue simple interest on their deposits. ### User Flow 1. The bank issues users tokens via the `issue` function. 2. A user deposits tokens via the `deposit` function. 3. Upon a user's request to withdraw, the bank calculates the appropriate amount of compound interest and pays the user the principal and interest via the `withdraw` function. Note that the program can be easily extended to include additional features such as a `transfer` function, which would allow users to transfer tokens to other users. ## Bugs You may have already guessed that this program has a few bugs. We list some of them below: - `withdraw` can only be invoked by the bank. A malicious bank could lock users' tokens by not invoking `withdraw`. - `withdraw` fails if the sum of the interest and principal is greater than the user's balance. - Users can increase their principal by depositing tokens multiple times, including immediately before withdrawal. - Integer division rounds down; if the calculated interest is too small, then it will be rounded down to zero. Can you find any others? ## Language Features and Concepts - `record` declarations - `assert_eq` - core functions, e.g. `BHP256::hash_to_field` - record ownership - loops and bounded iteration - mappings - finalize ## Running the Program Leo provides users with a command line interface for compiling and running Leo programs. ### Configuring Accounts The `.env` file contains a private key. This is the account that will be used to sign transactions and is checked for record ownership. When executing programs as different parties, be sure to set the `PRIVATE_KEY` field in `.env` to the appropriate values. See `./run.sh` for an example of how to run the program as different parties. The [Aleo SDK](https://github.com/AleoHQ/leo/tree/testnet3) provides an interface for generating new accounts. To generate a new account, navigate to [aleo.tools](https://aleo.tools). ### Providing inputs via the command line. ```bash leo run ... ``` See `./run.sh` for an example.