burn ATokens

Overview

• cache

• updateState

• get user's AToken balance + amount to withdraw

• validateWithdraw: confirm user has sufficient balance and asset isActive

• updateInterestRates

• collateral check

• burn ATokens

• Ensure existing loans are collateralized

burn ATokens

• burn calls _burnScaled

Amount of tokens burnt is scaled against current liquidity index

• amount = 100

• liquidity index = 1.1

• amountScaled = 100 / 1.1 = 90

This is to account for interest accrued.

If you are confused regarding balanceIncrease and _userState see: mint

_burnScaled has an interesting approach, in that it looks to mint or burn the difference between unbooked interest accrued and the burn amount.

• unbooked interest accrued: interest accumulated since last update that has not been minted

If balanceIncrease > amount

• interest accrued since last update is larger than burn amount

• mint the difference to the user as aTokens

If balanceIncrease <= amount

• burn amount exceeds interest accrued

• burn the difference from the user