Project #4: Fractional Wrapper

Objectives

  • Users can send a pre-specified erc-20 token (underlying) to an ERC20 contract(Fractional Wrapper).

  • Fractional Wrapper contract issues a number of Wrapper tokens to the sender, equal to the deposit multiplied by a fractional number, called exchange rate. Exchange rate is set by the contract owner.

  • This number is in the range of [0, 1e18], and available in increments of 10**-27. (ray).

  • At any point, a holder of Wrapper tokens can burn them to recover an amount of underlying equal to the amount of Wrapper tokens burned, divided by the exchange rate.

  • This Fractional Wrapper can conform to the ERC4626 specification.

Process

  1. User sends DAI to FWrapper.

  2. User receives wDAI, (wDAI = DAI * ex_rate)

  3. Exchange rate set by FWrapper owner

  4. Ex_rate is has decimal precision of 10**27 precision

  5. User can liquidate and get back underlying DAI, (wDAI is burnt) ---> dai_qty = wDAI/ex_rate

Contracts

  1. DAIToken - underlying

  2. FractionalWrapper - "vault w/ ex_rate"

  3. Ownable.sol - for onlyOwner modifier, applied on setExchangeRate

Both contracts are ERC20Mock, to issue tokens. FractionalWrapper must conform to ERC4626 specification.

  • all methods must be implemented

  • implementation of convert* and preview* will be identical in this case (no need to calculate some time-weighted average for convert*).

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