# PToken

`ReceiptVault` is the market contract for a single asset. It holds underlying tokens, mints pTokens, tracks borrows, and applies interest. Each asset has its own vault instance.

{% hint style="info" %}
Responsibilities

* Custody the underlying asset for one market.
* Mint and burn pTokens for suppliers.
* Track borrow balances and interest accrual.
* Enforce caps, reserve factor, and admin fee.
* Delegate risk checks to `SimplePeridottroller`.
  {% endhint %}

## Key Functions

* `deposit(user, amount)`\
  Transfers underlying from `user`, mints pTokens.
* `withdraw(user, ptoken_amount)`\
  Burns pTokens and returns underlying; checks liquidity via controller.
* `borrow(user, amount)`\
  Borrows underlying if controller allows.
* `repay(user, amount)`\
  Repays user debt (use a large amount for "max repay").
* `get_exchange_rate()`\
  Returns pToken → underlying exchange rate (scaled 1e6).
* `get_user_borrow_balance(user)`\
  Current borrow balance including accrued interest.

## Events

* `Deposit`
* `Withdraw`
* `Borrow`
* `Repay`
* `FlashLoan`