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77 lines
2.6 KiB
Markdown
77 lines
2.6 KiB
Markdown
<!-- # 🏦 Basic Bank -->
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<img alt="workshop/basic_bank" width="1412" src="../.resources/basic_bank.png">
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A simple-interest yielding bank account in Leo.
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## Summary
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This program implements a bank that issues tokens to users and allows users to deposit tokens to accrue simple interest on their deposits.
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### User Flow
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1. The bank issues users tokens via the `issue` function.
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2. A user deposits tokens via the `deposit` function.
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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.
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Note that the program can be easily extended to include addition features such as a `transfer` function, which would allow users to transfer tokens to other users.
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## Bugs
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You may have already guessed that this program has a few bugs. We list some of them below:
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- `withdraw` can only be invoked by the bank. A malicious bank could lock users' tokens by not invoking `withdraw`.
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- `withdraw` fails if the sum of the interest and principal is greater than the user's balance.
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- User's can increase their principal by depositing tokens multiple times, including immediately before withdrawl.
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- Integer division rounds down; if the calculated interest is too small, then it will be rounded down to zero.
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Can you find any others?
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## Language Features and Concepts
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- `record` declarations
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- `console.assert_eq`
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- core functions, e.g. `BHP256::hash`
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- record ownership
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- loops and bounded iteration
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- mappings
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- finalize
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## Running the Program
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Leo provides users with a command line interface for compiling and running Leo programs.
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Users may either specify input values via the command line or provide an input file in `inputs/`.
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### Configuring Accounts
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The `program.json` file contains a private key and address.
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This is the account that will be used to sign transactions and is checked for record ownership.
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When executing programs as different parties, be sure to set the `private_key` and `address` fields in `program.json` to the appropriate values.
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See `./run.sh` for an example of how to run the program as different parties.
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The [Aleo SDK](https://github.com/AleoHQ/leo/tree/testnet3) provides a command line interface for generating new accounts.
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To generate a new account, run
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```
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leo account new
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```
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### Providing inputs via the command line.
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1. Run
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```bash
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leo run <function_name> <input_1> <input_2> ...
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```
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See `./run.sh` for an example.
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### Using an input file.
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1. Modify `inputs/auction.in` with the desired inputs.
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2. Run
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```bash
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leo run <function_name>
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```
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For example,
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```bash
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leo run issue
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leo run deposit
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leo run withdraw
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```
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