# [bytes4 method_id][bytes8 ][bytes20 oracle] > A metapool is a pool where a stablecoin is paired against the LP token from another pool, a so-called base pool. A metapool is a pool where a stablecoin is paired against the LP token from another pool, a so-called base pool. :::deploy[Contract Source & Deployment] Source code available on [Github](https://github.com/curvefi/stableswap-ng/blob/bff1522b30819b7b240af17ccfb72b0effbf6c47/contracts/main/CurveStableSwapMetaNG.vy). ::: The deployment of metapools is permissionless and can be done via the [**`deploy_metapool`**](../../factory/stableswap-ng/deployer-api.md#deploy_metapool) function within the Stableswap-NG Factory. :::warning[Examples] The examples following each code block of the corresponding functions provide a basic illustration of input/output values. **When using the function in production, ensure not to set `_min_dy`, `_min_amount`, etc., to zero or other arbitrary numbers**. Otherwise, MEV bots may frontrun or sandwich your transaction, leading to a potential loss of funds. The examples are based on the USDV<>3CRV metapool: [0xc273fd237F23cb13296D0Cc2897F0B7A61e83387](https://etherscan.io/address/0xc273fd237F23cb13296D0Cc2897F0B7A61e83387#code). ::: :::info[**Oracle Methods Documentation**] Comprehensive documentation for Oracle Methods is available on a dedicated page, accessible [here](./oracles.md). ::: --- *The AMM metapool contract implementation utilizes two internal functions to transfer tokens/coins in and out of the pool and then accordingly update `stored_balances`.* *These function slightly differ to the ones from plain pools, as there needs to be some additional logic because of the basepools:* - **`_transfer_in()`** | Input | Type | Description | | ------------------------- | --------- | ------------------------------------------------------------------------------------------- | | `coin_metapool_idx` | `int128` | Metapool index of the input coin. | | `coin_basepool_idx` | `int128` | Basepool index of the input coin. | | `dx` | `uint256` | Amount to transfer in. | | `sender` | `address` | Address to transfer coins from. | | `expect_optimistic_transfer` | `bool` | `True` if the contract expects an optimistic coin transfer (see [`exchange_received()`](#exchange_received)). | | `is_base_pool_swap` | `bool` | If the exchange is a basepool swap (if `i and i > 0`); defaulted to `False`. | ```vyper @internal def _transfer_in( coin_metapool_idx: int128, coin_basepool_idx: int128, dx: uint256, sender: address, expect_optimistic_transfer: bool, is_base_pool_swap: bool = False, ) -> uint256: """ @notice Contains all logic to handle ERC20 token transfers. @param coin_metapool_idx metapool index of input coin @param coin_basepool_idx basepool index of input coin @param dx amount of `_coin` to transfer into the pool. @param sender address to transfer `_coin` from. @param expect_optimistic_transfer True if contract expects an optimistic coin transfer @param is_base_pool_swap Default is set to False. @return amount of coins received """ _input_coin: ERC20 = ERC20(coins[coin_metapool_idx]) _stored_balance: uint256 = self.stored_balances[coin_metapool_idx] _input_coin_is_in_base_pool: bool = False # Check if _transfer_in is being called by _exchange_underlying: if coin_basepool_idx >= 0 and coin_metapool_idx == 1: _input_coin = ERC20(BASE_COINS[coin_basepool_idx]) _input_coin_is_in_base_pool = True _dx: uint256 = _input_coin.balanceOf(self) # ------------------------- Handle Transfers ----------------------------- if expect_optimistic_transfer: if not _input_coin_is_in_base_pool: _dx = _dx - _stored_balance assert _dx >= dx # dev: pool did not receive tokens for swap else: assert dx > 0 # dev : do not transferFrom 0 tokens into the pool assert _input_coin.transferFrom( sender, self, dx, default_return_value=True ) _dx = _input_coin.balanceOf(self) - _dx # ------------ Check if liquidity needs to be added somewhere ------------ if _input_coin_is_in_base_pool: if is_base_pool_swap: return _dx # <----- _exchange_underlying: all input goes to swap. # So, we will not increment self.stored_balances for metapool_idx. # Swap involves base <> meta pool interaction. Add incoming base pool # token to the base pool, mint _dx base pool LP token (idx 1) and add # that to self.stored_balances and return that instead. _dx = self._meta_add_liquidity(_dx, coin_basepool_idx) # ----------------------- Update Stored Balances ------------------------- self.stored_balances[coin_metapool_idx] += _dx return _dx @internal def _meta_add_liquidity(dx: uint256, base_i: int128) -> uint256: coin_i: address = coins[MAX_METAPOOL_COIN_INDEX] x: uint256 = ERC20(coin_i).balanceOf(self) if BASE_N_COINS == 2: base_inputs: uint256[2] = empty(uint256[2]) base_inputs[base_i] = dx StableSwap2(BASE_POOL).add_liquidity(base_inputs, 0) if BASE_N_COINS == 3: base_inputs: uint256[3] = empty(uint256[3]) base_inputs[base_i] = dx StableSwap3(BASE_POOL).add_liquidity(base_inputs, 0) return ERC20(coin_i).balanceOf(self) - x ``` - **`_transfer_out()`** | Input | Type | Description | | ---------- | --------- | ----------------------------------------- | | `coin_idx` | `int128` | Index value of the token to transfer out. | | `_amount` | `uint256` | Amount to transfer out. | | `receiver` | `address` | Address to send the tokens to. | ```vyper stored_balances: DynArray[uint256, MAX_COINS] @internal def _transfer_out( _coin_idx: int128, _amount: uint256, receiver: address ): """ @notice Transfer a single token from the pool to receiver. @param _coin_idx Index of the token to transfer out @param _amount Amount of token to transfer out @param receiver Address to send the tokens to """ coin_balance: uint256 = ERC20(coins[_coin_idx]).balanceOf(self) # ------------------------- Handle Transfers ----------------------------- assert ERC20(coins[_coin_idx]).transfer( receiver, _amount, default_return_value=True ) # ----------------------- Update Stored Balances ------------------------- self.stored_balances[_coin_idx] = coin_balance - _amount ``` :::info[Methods with underlying coins] In metapools, `coin[0]` is always the metapool token, and `coin[1]` is always the basepool token. When working with the basepool underlying tokens such as `exchange_underlying` and others, the coin indices of the basepool are appended after `coin[0]`, which is the metapool token. E.g., in the USDV<>3CRV pool: `coin[0]` = USDV, `coin[1]` = DAI, `coin[2]` = USDC, and `coin[3]` = USDT. ::: --- ## Exchange Methods *Three functions for token exchanges:* - The regular `exchange` function. - A novel `exchange_received` function that executes a token exchange based on the internal balances of the pool. - Additionally, the metapool implementation includes an `exchange_underlying` function, which allows tokens to be exchanged with the underlying tokens the asset is paired against. For example, swapping USDV for USDT in the USDV<>3CRV pool. ### `exchange` ::::description[`StableSwap.exchange(i: int128, j: int128, _dx: uint256, _min_dy: uint256, _receiver: address = msg.sender) -> uint256:`] :::warning This exchange swaps between the metapool token and the basepool LP token. coin[0] is always the metapool token and coin[1] is the basepool LP token. To exchange the metapool token against underlying coins, one needs to use the `exchange_underlying` function. ::: Function to exchange `_dx` amount of coin `i` for coin `j` and receive a minimum amount of `_min_dy`. Returns: amount of output coin received (`uint256`). Emits: `TokenExchange` | Input | Type | Description | | ----------- | --------- | ------------------------------------------------------ | | `i` | `int128` | Index value of the input coin. | | `j` | `int128` | Index value of the output coin. | | `_dx` | `uint256` | Amount of coin `i` being exchanged. | | `_min_dy` | `uint256` | Minimum amount of coin `j` to receive. | | `_receiver` | `address` | Receiver of the output tokens; defaults to msg.sender. | ```vyper event TokenExchange: buyer: indexed(address) sold_id: int128 tokens_sold: uint256 bought_id: int128 tokens_bought: uint256 @external @nonreentrant('lock') def exchange( i: int128, j: int128, _dx: uint256, _min_dy: uint256, _receiver: address = msg.sender, ) -> uint256: """ @notice Perform an exchange between two coins @dev Index values can be found via the `coins` public getter method @param i Index value for the coin to send @param j Index value of the coin to recieve @param _dx Amount of `i` being exchanged @param _min_dy Minimum amount of `j` to receive @return Actual amount of `j` received """ return self._exchange( msg.sender, i, j, _dx, _min_dy, _receiver, False ) @internal def _exchange( sender: address, i: int128, j: int128, _dx: uint256, _min_dy: uint256, receiver: address, expect_optimistic_transfer: bool ) -> uint256: assert i != j # dev: coin index out of range assert _dx > 0 # dev: do not exchange 0 coins rates: DynArray[uint256, MAX_COINS] = self._stored_rates() old_balances: DynArray[uint256, MAX_COINS] = self._balances() xp: DynArray[uint256, MAX_COINS] = self._xp_mem(rates, old_balances) # --------------------------- Do Transfer in ----------------------------- # `dx` is whatever the pool received after ERC20 transfer: dx: uint256 = self._transfer_in( i, -1, # <----- we're not handling underlying coins here. _dx, sender, expect_optimistic_transfer ) # ------------------------------- Exchange ------------------------------- # xp[i] + dx * rates[i] / PRECISION x: uint256 = xp[i] + unsafe_div(dx * rates[i], PRECISION) dy: uint256 = self.__exchange(x, xp, rates, i, j) assert dy >= _min_dy, "Exchange resulted in fewer coins than expected" # --------------------------- Do Transfer out ---------------------------- self._transfer_out(j, dy, receiver) # ------------------------------------------------------------------------ log TokenExchange(msg.sender, i, _dx, j, dy) return dy @internal def __exchange( x: uint256, _xp: DynArray[uint256, MAX_COINS], rates: DynArray[uint256, MAX_COINS], i: int128, j: int128, ) -> uint256: amp: uint256 = self._A() D: uint256 = math.get_D(_xp, amp, N_COINS) y: uint256 = math.get_y(i, j, x, _xp, amp, D, N_COINS) dy: uint256 = _xp[j] - y - 1 # -1 just in case there were some rounding errors dy_fee: uint256 = dy * self._dynamic_fee((_xp[i] + x) / 2, (_xp[j] + y) / 2, self.fee) / FEE_DENOMINATOR # Convert all to real units dy = (dy - dy_fee) * PRECISION / rates[j] self.admin_balances[j] += ( unsafe_div(dy_fee * admin_fee, FEE_DENOMINATOR) # dy_fee * admin_fee / FEE_DENOMINATOR ) * PRECISION / rates[j] # Calculate and store state prices: xp: DynArray[uint256, MAX_COINS] = _xp xp[i] = x xp[j] = y # D is not changed because we did not apply a fee self.upkeep_oracles(xp, amp, D) return dy ``` ```shell >>> StableSwap.get_balances() [4183467888075, 2556883713184291687567176] >>> StableSwap.exchange(0, 1, 10**6, 0) 971169724887534588 >>> StableSwap.get_balances() [4183468888075, 2556882741963895491313748] ``` :::: ### `exchange_received` ::::description[`StableSwap.exchange_received(i: int128, j: int128, _dx: uint256, _min_dy: uint256, _receiver: address) -> uint256:`] :::danger `exchange_received` will revert if the pool contains a rebasing asset. A pool that contains a rebasing token should have an `asset_type` of 2. If this is not the case, the pool is using an incorrect implementation, and rebases can be stolen. ::: Function to exchange `_dx` amount of coin `i` for coin `j`, receiving a minimum amount of `_min_dy`. This is done without actually transferring the coins into the pool within the same call. The exchange is based on the change in the balance of coin `i`, eliminating the need to grant approval to the contract. This function does only swap between the token paird against the basepool and the basepool tokens. The method can not be used to exchange for underlying coins of the basepool. **A detailed article can be found here: https://blog.curvemonitor.com/posts/exchange-received/.**Returns: amount of output coin received (`uint256`). Emits: `TokenExchange` | Input | Type | Description | | ------------ | ---------- | -------------------------------------------------- | | `i` | `int128` | Index value of input coin. | | `j` | `int128` | Index value of output coin. | | `_dx` | `uint256` | Amount of coin `i` being exchanged. | | `_min_dy` | `uint256` | Minimum amount of coin `j` to receive. | | `_receiver` | `address` | Receiver of the output tokens; defaults to `msg.sender`. | ```vyper event TokenExchange: buyer: indexed(address) sold_id: int128 tokens_sold: uint256 bought_id: int128 tokens_bought: uint256 @external @nonreentrant('lock') def exchange_received( i: int128, j: int128, _dx: uint256, _min_dy: uint256, _receiver: address, ) -> uint256: """ @notice Perform an exchange between two coins without transferring token in @dev The contract swaps tokens based on a change in balance of coin[i]. The dx = ERC20(coin[i]).balanceOf(self) - self.stored_balances[i]. Users of this method are dex aggregators, arbitrageurs, or other users who do not wish to grant approvals to the contract: they would instead send tokens directly to the contract and call `exchange_received`. Note: This is disabled if pool contains rebasing tokens. @param i Index value for the coin to send @param j Index valie of the coin to recieve @param _dx Amount of `i` being exchanged @param _min_dy Minimum amount of `j` to receive @return Actual amount of `j` received """ assert not POOL_IS_REBASING_IMPLEMENTATION # dev: exchange_received not supported if pool contains rebasing tokens return self._exchange( msg.sender, i, j, _dx, _min_dy, _receiver, True, # <--------------------------------------- swap optimistically. ) @internal def _exchange( sender: address, i: int128, j: int128, _dx: uint256, _min_dy: uint256, receiver: address, expect_optimistic_transfer: bool ) -> uint256: assert i != j # dev: coin index out of range assert _dx > 0 # dev: do not exchange 0 coins rates: DynArray[uint256, MAX_COINS] = self._stored_rates() old_balances: DynArray[uint256, MAX_COINS] = self._balances() xp: DynArray[uint256, MAX_COINS] = self._xp_mem(rates, old_balances) # --------------------------- Do Transfer in ----------------------------- # `dx` is whatever the pool received after ERC20 transfer: dx: uint256 = self._transfer_in( i, -1, # <----- we're not handling underlying coins here. _dx, sender, expect_optimistic_transfer ) # ------------------------------- Exchange ------------------------------- # xp[i] + dx * rates[i] / PRECISION x: uint256 = xp[i] + unsafe_div(dx * rates[i], PRECISION) dy: uint256 = self.__exchange(x, xp, rates, i, j) assert dy >= _min_dy, "Exchange resulted in fewer coins than expected" # --------------------------- Do Transfer out ---------------------------- self._transfer_out(j, dy, receiver) # ------------------------------------------------------------------------ log TokenExchange(msg.sender, i, _dx, j, dy) return dy @internal def __exchange( x: uint256, _xp: DynArray[uint256, MAX_COINS], rates: DynArray[uint256, MAX_COINS], i: int128, j: int128, ) -> uint256: amp: uint256 = self._A() D: uint256 = math.get_D(_xp, amp, N_COINS) y: uint256 = math.get_y(i, j, x, _xp, amp, D, N_COINS) dy: uint256 = _xp[j] - y - 1 # -1 just in case there were some rounding errors dy_fee: uint256 = dy * self._dynamic_fee((_xp[i] + x) / 2, (_xp[j] + y) / 2, self.fee) / FEE_DENOMINATOR # Convert all to real units dy = (dy - dy_fee) * PRECISION / rates[j] self.admin_balances[j] += ( unsafe_div(dy_fee * admin_fee, FEE_DENOMINATOR) # dy_fee * admin_fee / FEE_DENOMINATOR ) * PRECISION / rates[j] # Calculate and store state prices: xp: DynArray[uint256, MAX_COINS] = _xp xp[i] = x xp[j] = y # D is not changed because we did not apply a fee self.upkeep_oracles(xp, amp, D) return dy ``` ```shell >>> USDV.transfer("0xc273fd237F23cb13296D0Cc2897F0B7A61e83387", 10**6) >>> StableSwap.received(0, 1, 10**6, 0) 998545692103751082 ``` :::note More information on this method [here](../overview.md#exchange_received). ::: :::: ### `exchange_underlying` ::::description[`StableSwap.exchange_underlying(i: int128, j: int128, _dx: uint256, _min_dy: uint256, _receiver: address = msg.sender) -> uint256:`] Function to exchange `_dx` amount of the underlying coin `i` for the underlying coin `j` and receive a minimum amount of `_min_dy`. Index values are the `coins` followed by the `base_coins`, where the base pool LP token is not included as a value. Returns: amount of output coin received (`uint256`). Emits: `TokenExchangeUnderlying` | Input | Type | Description | | ----------- | -------| ----| | `i` | `int128` | Index value of underlying input coin. | | `j` | `int128` | Index value of underlying output coin. | | `_dx` | `uint256` | Amount of coin `i` being exchanged. | | `_min_dy` | `uint256` | Minimum amount of coin `j` to receive. | | `receiver` | `address` | Receiver of the output tokens; defaults to msg.sender. | ```vyper event TokenExchangeUnderlying: buyer: indexed(address) sold_id: int128 tokens_sold: uint256 bought_id: int128 tokens_bought: uint256 @external @nonreentrant('lock') def exchange_underlying( i: int128, j: int128, _dx: uint256, _min_dy: uint256, _receiver: address = msg.sender, ) -> uint256: """ @notice Perform an exchange between two underlying coins @param i Index value for the underlying coin to send @param j Index value of the underlying coin to receive @param _dx Amount of `i` being exchanged @param _min_dy Minimum amount of `j` to receive @param _receiver Address that receives `j` @return Actual amount of `j` received """ return self._exchange_underlying( msg.sender, i, j, _dx, _min_dy, _receiver, False ) @internal def _exchange_underlying( sender: address, i: int128, j: int128, _dx: uint256, _min_dy: uint256, receiver: address, expect_optimistic_transfer: bool = False ) -> uint256: rates: DynArray[uint256, MAX_COINS] = self._stored_rates() old_balances: DynArray[uint256, MAX_COINS] = self._balances() xp: DynArray[uint256, MAX_COINS] = self._xp_mem(rates, old_balances) dy: uint256 = 0 base_i: int128 = 0 base_j: int128 = 0 meta_i: int128 = 0 meta_j: int128 = 0 x: uint256 = 0 output_coin: address = empty(address) # ------------------------ Determine coin indices ------------------------ # Get input coin indices: if i > 0: base_i = i - MAX_METAPOOL_COIN_INDEX meta_i = 1 # Get output coin and indices: if j == 0: output_coin = coins[0] else: base_j = j - MAX_METAPOOL_COIN_INDEX meta_j = 1 output_coin = BASE_COINS[base_j] # --------------------------- Do Transfer in ----------------------------- # If incoming coin is supposed to go to the base pool, the _transfer_in # method will add_liquidity in the base pool and return dx_w_fee LP tokens dx_w_fee: uint256 = self._transfer_in( meta_i, base_i, _dx, sender, expect_optimistic_transfer, (i > 0 and j > 0), # <--- if True: do not add liquidity to base pool. ) # ------------------------------- Exchange ------------------------------- if i == 0 or j == 0: # meta swap if i == 0: # xp[i] + dx_w_fee * rates[i] / PRECISION x = xp[i] + unsafe_div(dx_w_fee * rates[i], PRECISION) else: # dx_w_fee is the number of base_pool LP tokens minted after # base_pool.add_liquidity in self._transfer_in # dx_w_fee * rates[MAX_METAPOOL_COIN_INDEX] / PRECISION x = unsafe_div(dx_w_fee * rates[MAX_METAPOOL_COIN_INDEX], PRECISION) x += xp[MAX_METAPOOL_COIN_INDEX] dy = self.__exchange(x, xp, rates, meta_i, meta_j) # Adjust stored balances of meta-level tokens: self.stored_balances[meta_j] -= dy # Withdraw from the base pool if needed if j > 0: out_amount: uint256 = ERC20(output_coin).balanceOf(self) StableSwap(BASE_POOL).remove_liquidity_one_coin(dy, base_j, 0) dy = ERC20(output_coin).balanceOf(self) - out_amount assert dy >= _min_dy else: # base pool swap (user should swap at base pool for better gas) dy = ERC20(output_coin).balanceOf(self) StableSwap(BASE_POOL).exchange(base_i, base_j, dx_w_fee, _min_dy) dy = ERC20(output_coin).balanceOf(self) - dy # --------------------------- Do Transfer out ---------------------------- assert ERC20(output_coin).transfer(receiver, dy, default_return_value=True) # ------------------------------------------------------------------------ log TokenExchangeUnderlying(sender, i, _dx, j, dy) return dy @internal def __exchange( x: uint256, _xp: DynArray[uint256, MAX_COINS], rates: DynArray[uint256, MAX_COINS], i: int128, j: int128, ) -> uint256: amp: uint256 = self._A() D: uint256 = math.get_D(_xp, amp, N_COINS) y: uint256 = math.get_y(i, j, x, _xp, amp, D, N_COINS) dy: uint256 = _xp[j] - y - 1 # -1 just in case there were some rounding errors dy_fee: uint256 = dy * self._dynamic_fee((_xp[i] + x) / 2, (_xp[j] + y) / 2, self.fee) / FEE_DENOMINATOR # Convert all to real units dy = (dy - dy_fee) * PRECISION / rates[j] self.admin_balances[j] += ( unsafe_div(dy_fee * admin_fee, FEE_DENOMINATOR) # dy_fee * admin_fee / FEE_DENOMINATOR ) * PRECISION / rates[j] # Calculate and store state prices: xp: DynArray[uint256, MAX_COINS] = _xp xp[i] = x xp[j] = y # D is not changed because we did not apply a fee self.upkeep_oracles(xp, amp, D) return dy ``` ```shell >>> StableSwap.exchange_underlying(0, 1, 10**6, 0) 998545692103751082 >>> StableSwap.exchange_underlying(0, 2, 10**6, 0) 998565 ``` :::: ### `get_dy` ::::description[`StableSwap.get_dy(i: int128, j: int128, dx: uint256) -> uint256`] Function to calculate the predicted output amount `j` to receive at the pool's current state given an input of `dx` amount of coin `i`. This is just a simple getter method; the calculation logic is within the CurveStableSwapNGViews contract. See [here](../utility-contracts/views.md#get_dy). Returns: predicted output amount of `j` (`uint256`). | Input | Type | Description | | ------ | -------- | ------------------------------------------ | | `i` | `int128` | Index value of input coin. | | `j` | `int128` | Index value of output coin. | | `dx` | `uint256`| Amount of input coin being exchanged. | ```vyper interface StableSwapViews: def get_dx(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def get_dx_underlying(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy_underlying(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def dynamic_fee(i: int128, j: int128, pool: address) -> uint256: view def calc_token_amount( _amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool, _pool: address ) -> uint256: view @view @external def get_dy(i: int128, j: int128, dx: uint256) -> uint256: """ @notice Calculate the current output dy given input dx @dev Index values can be found via the `coins` public getter method @param i Index value for the coin to send @param j Index valie of the coin to recieve @param dx Amount of `i` being exchanged @return Amount of `j` predicted """ return StableSwapViews(factory.views_implementation()).get_dy(i, j, dx, self) ``` ```vyper @view @external def get_dy(i: int128, j: int128, dx: uint256, pool: address) -> uint256: """ @notice Calculate the current output dy given input dx @dev Index values can be found via the `coins` public getter method @param i Index value for the coin to send @param j Index valie of the coin to recieve @param dx Amount of `i` being exchanged @return Amount of `j` predicted """ N_COINS: uint256 = StableSwapNG(pool).N_COINS() rates: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) rates, balances, xp = self._get_rates_balances_xp(pool, N_COINS) amp: uint256 = StableSwapNG(pool).A() * A_PRECISION D: uint256 = self.get_D(xp, amp, N_COINS) x: uint256 = xp[i] + (dx * rates[i] / PRECISION) y: uint256 = self.get_y(i, j, x, xp, amp, D, N_COINS) dy: uint256 = xp[j] - y - 1 base_fee: uint256 = StableSwapNG(pool).fee() fee_multiplier: uint256 = StableSwapNG(pool).offpeg_fee_multiplier() fee: uint256 = self._dynamic_fee((xp[i] + x) / 2, (xp[j] + y) / 2, base_fee, fee_multiplier) * dy / FEE_DENOMINATOR return (dy - fee) * PRECISION / rates[j] ``` ```shell >>> StableSwap.get_dy(0, 1, 10**6) 971173697952445825 ``` :::: ### `get_dy_underlying` ::::description[`StableSwap.get_dy_underlying(i: int128, j: int128, dx: uint256) -> uint256:`] Function to calculate the predicted output amount `j` to receive given an input of `dx` amount of coin `i`, including underlying coins. Index values are the `coins` followed by the `base_coins`, where the base pool LP token is not included as a value. Returns: predicted amount of `j` (`uint256`). | Input | Type | Description | | ----------- | -------| ----| | `i` | `int128` | Index value of input coin. | | `j` | `int128` | Index value of output coin. | | `dx` | `uint256` | Amount of input coin being exchanged. | ```vyper interface StableSwapViews: def get_dx(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def get_dx_underlying(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy_underlying(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def dynamic_fee(i: int128, j: int128, pool: address) -> uint256: view def calc_token_amount( _amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool, _pool: address ) -> uint256: view @view @external def get_dy_underlying(i: int128, j: int128, dx: uint256) -> uint256: return StableSwapViews(factory.views_implementation()).get_dy_underlying(i, j, dx, self) ``` ```vyper @view @external def get_dy_underlying( i: int128, j: int128, dx: uint256, pool: address, ) -> uint256: """ @notice Calculate the current output dy given input dx on underlying @dev Index values can be found via the `coins` public getter method @param i Index value for the coin to send @param j Index valie of the coin to recieve @param dx Amount of `i` being exchanged @return Amount of `j` predicted """ N_COINS: uint256 = StableSwapNG(pool).N_COINS() MAX_COIN: int128 = convert(N_COINS, int128) - 1 BASE_POOL: address = StableSwapNG(pool).BASE_POOL() rates: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) rates, balances, xp = self._get_rates_balances_xp(pool, N_COINS) x: uint256 = 0 base_i: int128 = 0 base_j: int128 = 0 meta_i: int128 = 0 meta_j: int128 = 0 if i != 0: base_i = i - MAX_COIN meta_i = 1 if j != 0: base_j = j - MAX_COIN meta_j = 1 if i == 0: x = xp[i] + dx * rates[0] / 10**18 else: if j == 0: # i is from BasePool base_n_coins: uint256 = StableSwapNG(pool).BASE_N_COINS() x = self._base_calc_token_amount( dx, base_i, base_n_coins, BASE_POOL, True ) * rates[1] / PRECISION # Adding number of pool tokens x += xp[1] else: # If both are from the base pool return StableSwapNG(BASE_POOL).get_dy(base_i, base_j, dx) # This pool is involved only when in-pool assets are used amp: uint256 = StableSwapNG(pool).A() * A_PRECISION D: uint256 = self.get_D(xp, amp, N_COINS) y: uint256 = self.get_y(meta_i, meta_j, x, xp, amp, D, N_COINS) dy: uint256 = xp[meta_j] - y - 1 # calculate output after subtracting dynamic fee base_fee: uint256 = StableSwapNG(pool).fee() fee_multiplier: uint256 = StableSwapNG(pool).offpeg_fee_multiplier() dynamic_fee: uint256 = self._dynamic_fee((xp[meta_i] + x) / 2, (xp[meta_j] + y) / 2, base_fee, fee_multiplier) dy = (dy - dynamic_fee * dy / FEE_DENOMINATOR) # If output is going via the metapool if j == 0: dy = dy * 10**18 / rates[0] else: # j is from BasePool # The fee is already accounted for dy = StableSwapNG(BASE_POOL).calc_withdraw_one_coin(dy * PRECISION / rates[1], base_j) return dy ``` ```shell >>> StableSwap.get_dy_underlying(0, 1, 10**6) 999713269803541066 >>> StableSwap.get_dy_underlying(0, 2, 10**6) 998565 >>> StableSwap.get_dy_underlying(0, 3, 10**6) 999171 >>> StableSwap.get_dy_underlying(3, 0, 10**6) 1000587 ``` :::: ### `get_dx` ::::description[`StableSwap.get_dx(i: int128, j: int128, dy: uint256) -> uint256:`] Function to calculate the predicted input amount `i` to receive `dy` of coin `j` at the pool's current state. This is just a simple getter method; the calculation logic is within the CurveStableSwapNGViews contract. See [here](../utility-contracts/views.md#get_dx). Returns: predicted input amount of `i` (`uint256`). | Input | Type | Description | | ------ | -------- | ------------------------------------------ | | `i` | `int128` | Index value of input coin. | | `j` | `int128` | Index value of output coin. | | `dy` | `uint256`| Amount of output coin received. | ```vyper interface StableSwapViews: def get_dx(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def dynamic_fee(i: int128, j: int128, pool: address) -> uint256: view def calc_token_amount( _amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool, _pool: address ) -> uint256: view @view @external def get_dx(i: int128, j: int128, dy: uint256) -> uint256: """ @notice Calculate the current input dx given output dy @dev Index values can be found via the `coins` public getter method @param i Index value for the coin to send @param j Index valie of the coin to recieve @param dy Amount of `j` being received after exchange @return Amount of `i` predicted """ return StableSwapViews(factory.views_implementation()).get_dx(i, j, dy, self) ``` ```vyper @view @external def get_dx(i: int128, j: int128, dy: uint256, pool: address) -> uint256: """ @notice Calculate the current input dx given output dy @dev Index values can be found via the `coins` public getter method @param i Index value for the coin to send @param j Index valie of the coin to recieve @param dy Amount of `j` being received after exchange @return Amount of `i` predicted """ N_COINS: uint256 = StableSwapNG(pool).N_COINS() return self._get_dx(i, j, dy, pool, False, N_COINS) @view @internal def _get_dx( i: int128, j: int128, dy: uint256, pool: address, static_fee: bool, N_COINS: uint256 ) -> uint256: rates: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) rates, balances, xp = self._get_rates_balances_xp(pool, N_COINS) amp: uint256 = StableSwapNG(pool).A() * A_PRECISION D: uint256 = self.get_D(xp, amp, N_COINS) base_fee: uint256 = StableSwapNG(pool).fee() dy_with_fee: uint256 = dy * rates[j] / PRECISION + 1 fee: uint256 = base_fee if not static_fee: fee_multiplier: uint256 = StableSwapNG(pool).offpeg_fee_multiplier() fee = self._dynamic_fee(xp[i], xp[j], base_fee, fee_multiplier) y: uint256 = xp[j] - dy_with_fee * FEE_DENOMINATOR / (FEE_DENOMINATOR - fee) x: uint256 = self.get_y(j, i, y, xp, amp, D, N_COINS) return (x - xp[i]) * PRECISION / rates[i] ``` ```shell >>> StableSwap.get_dx(0, 1 10**6) 971173697952445825 ``` :::: ### `get_dx_underlying` ::::description[`StableSwap.get_dx_underlying(i: int128, j: int128, dy: uint256) -> uint256:`] Function to calculate the predicted input amount `i` to receive `dy` of coin `j`, including underlying coins. Index values are the `coins` followed by the `base_coins`, where the base pool LP token is not included as a value. Returns: predicted amount of `i` (`uint256`). | Input | Type | Description | | ----------- | -------| ----| | `i` | `int128` | Index value of input coin. | | `j` | `int128` | Index value of output coin. | | `dy` | `uint256` | Amount of output coin received. | ```vyper interface StableSwapViews: def get_dx(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def get_dx_underlying(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy_underlying(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def dynamic_fee(i: int128, j: int128, pool: address) -> uint256: view def calc_token_amount( _amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool, _pool: address ) -> uint256: view @view @external def get_dx_underlying(i: int128, j: int128, dy: uint256) -> uint256: return StableSwapViews(factory.views_implementation()).get_dx_underlying(i, j, dy, self) ``` ```vyper @view @external def get_dx_underlying( i: int128, j: int128, dy: uint256, pool: address, ) -> uint256: BASE_POOL: address = StableSwapNG(pool).BASE_POOL() BASE_N_COINS: uint256 = StableSwapNG(pool).BASE_N_COINS() N_COINS: uint256 = StableSwapNG(pool).N_COINS() base_pool_has_static_fee: bool = self._has_static_fee(BASE_POOL) # CASE 1: Swap does not involve Metapool at all. In this case, we kindly as the user # to use the right pool for their swaps. if min(i, j) > 0: raise "Not a Metapool Swap. Use Base pool." # CASE 2: # 1. meta token_0 of (unknown amount) > base pool lp_token # 2. base pool lp_token > calc_withdraw_one_coin gives dy amount of (j-1)th base coin # So, need to do the following calculations: # 1. calc_token_amounts on base pool for depositing liquidity on (j-1)th token > lp_tokens. # 2. get_dx on metapool for i = 0, and j = 1 (base lp token) with amt calculated in (1). if i == 0: # Calculate LP tokens that are burnt to receive dy amount of base_j tokens. lp_amount_burnt: uint256 = self._base_calc_token_amount( dy, j - 1, BASE_N_COINS, BASE_POOL, False ) return self._get_dx(0, 1, lp_amount_burnt, pool, False, N_COINS) # CASE 3: Swap in token i-1 from base pool and swap out dy amount of token 0 (j) from metapool. # 1. deposit i-1 token from base pool > receive base pool lp_token # 2. swap base pool lp token > 0th token of the metapool # So, need to do the following calculations: # 1. get_dx on metapool with i = 0, j = 1 > gives how many base lp tokens are required for receiving # dy amounts of i-1 tokens from the metapool # 2. We have number of lp tokens: how many i-1 base pool coins are needed to mint that many tokens? # We don't have a method where user inputs lp tokens and it gives number of coins of (i-1)th token # is needed to mint that many base_lp_tokens. Instead, we will use calc_withdraw_one_coin. That's # close enough. lp_amount_required: uint256 = self._get_dx(1, 0, dy, pool, False, N_COINS) return StableSwapNG(BASE_POOL).calc_withdraw_one_coin(lp_amount_required, i-1) @view @internal def _get_dx( i: int128, j: int128, dy: uint256, pool: address, static_fee: bool, N_COINS: uint256 ) -> uint256: rates: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) rates, balances, xp = self._get_rates_balances_xp(pool, N_COINS) amp: uint256 = StableSwapNG(pool).A() * A_PRECISION D: uint256 = self.get_D(xp, amp, N_COINS) base_fee: uint256 = StableSwapNG(pool).fee() dy_with_fee: uint256 = dy * rates[j] / PRECISION + 1 fee: uint256 = base_fee if not static_fee: fee_multiplier: uint256 = StableSwapNG(pool).offpeg_fee_multiplier() fee = self._dynamic_fee(xp[i], xp[j], base_fee, fee_multiplier) y: uint256 = xp[j] - dy_with_fee * FEE_DENOMINATOR / (FEE_DENOMINATOR - fee) x: uint256 = self.get_y(j, i, y, xp, amp, D, N_COINS) return (x - xp[i]) * PRECISION / rates[i] @view @external def calc_withdraw_one_coin(_burn_amount: uint256, i: int128, pool: address) -> uint256: # First, need to calculate # * Get current D # * Solve Eqn against y_i for D - _token_amount amp: uint256 = StableSwapNG(pool).A() * A_PRECISION N_COINS: uint256 = StableSwapNG(pool).N_COINS() rates: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) rates, balances, xp = self._get_rates_balances_xp(pool, N_COINS) D0: uint256 = self.get_D(xp, amp, N_COINS) total_supply: uint256 = StableSwapNG(pool).totalSupply() D1: uint256 = D0 - _burn_amount * D0 / total_supply new_y: uint256 = self.get_y_D(amp, i, xp, D1, N_COINS) ys: uint256 = (D0 + D1) / (2 * N_COINS) base_fee: uint256 = StableSwapNG(pool).fee() * N_COINS / (4 * (N_COINS - 1)) fee_multiplier: uint256 = StableSwapNG(pool).offpeg_fee_multiplier() xp_reduced: DynArray[uint256, MAX_COINS] = xp xp_j: uint256 = 0 xavg: uint256 = 0 dynamic_fee: uint256 = 0 for j in range(MAX_COINS): if j == N_COINS: break dx_expected: uint256 = 0 xp_j = xp[j] if convert(j, int128) == i: dx_expected = xp_j * D1 / D0 - new_y xavg = (xp[j] + new_y) / 2 else: dx_expected = xp_j - xp_j * D1 / D0 xavg = xp[j] dynamic_fee = self._dynamic_fee(xavg, ys, base_fee, fee_multiplier) xp_reduced[j] = xp_j - dynamic_fee * dx_expected / FEE_DENOMINATOR dy: uint256 = xp_reduced[i] - self.get_y_D(amp, i, xp_reduced, D1, N_COINS) dy = (dy - 1) * PRECISION / rates[i] # Withdraw less to account for rounding errors return dy ``` ```shell >>> StableSwap.get_dx_underlying(0, 1, 10**6) 998546308572137376 >>> StableSwap.get_dx_underlying(0, 3, 10**6) 999171 ``` :::: --- ## Adding and Removing Liquidity There are no restrictions on how liquidity can be added or removed. Liquidity can be provided or removed in any proportion. However, there are fees associated with adding and removing liquidity that depend on the balances within the pool. ### `add_liquidity` ::::description[`StableSwap.add_liquidity(_amounts: DynArray[uint256, MAX_COINS], _min_mint_amount: uint256, _receiver: address = msg.sender) -> uint256:`] Function to add liquidity into the pool and mint a minimum of `_min_mint_amount` of the corresponding LP tokens to `_receiver`. A value for the minimum amount is used to prevent being front-run by MEV bots. Returns: amount of LP tokens received (`uint256`). Emits: `Transfer` and `AddLiquidity` | Input | Type | Description | | ------------ | ------------------------------ | -------------------------------------------------- | | `_amounts` | `DynArray[uint256, MAX_COINS]`| List of coin amounts to deposit. | | `_min_amount`| `uint256` | Minimum amount of LP tokens to mint. | | `_receiver` | `address` | Receiver of the LP tokens; defaults to `msg.sender`.| ```vyper event Transfer: sender: indexed(address) receiver: indexed(address) value: uint256 event AddLiquidity: provider: indexed(address) token_amounts: DynArray[uint256, MAX_COINS] fees: DynArray[uint256, MAX_COINS] invariant: uint256 token_supply: uint256 @external @nonreentrant('lock') def add_liquidity( _amounts: DynArray[uint256, MAX_COINS], _min_mint_amount: uint256, _receiver: address = msg.sender ) -> uint256: """ @notice Deposit coins into the pool @param _amounts List of amounts of coins to deposit @param _min_mint_amount Minimum amount of LP tokens to mint from the deposit @param _receiver Address that owns the minted LP tokens @return Amount of LP tokens received by depositing """ amp: uint256 = self._A() old_balances: DynArray[uint256, MAX_COINS] = self._balances() rates: DynArray[uint256, MAX_COINS] = self._stored_rates() # Initial invariant D0: uint256 = self.get_D_mem(rates, old_balances, amp) total_supply: uint256 = self.total_supply new_balances: DynArray[uint256, MAX_COINS] = old_balances # -------------------------- Do Transfers In ----------------------------- for i in range(N_COINS_128): if _amounts[i] > 0: new_balances[i] += self._transfer_in( i, -1, # <--- we're not handling underlying coins here _amounts[i], msg.sender, False, # expect_optimistic_transfer ) else: assert total_supply != 0 # dev: initial deposit requires all coins # ------------------------------------------------------------------------ # Invariant after change D1: uint256 = self.get_D_mem(rates, new_balances, amp) assert D1 > D0 # We need to recalculate the invariant accounting for fees # to calculate fair user's share fees: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) mint_amount: uint256 = 0 if total_supply > 0: ideal_balance: uint256 = 0 difference: uint256 = 0 new_balance: uint256 = 0 ys: uint256 = (D0 + D1) / N_COINS xs: uint256 = 0 _dynamic_fee_i: uint256 = 0 # Only account for fees if we are not the first to deposit # base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1)) # unsafe math is safu here: base_fee: uint256 = unsafe_div(unsafe_mul(self.fee, N_COINS), 4) for i in range(N_COINS_128): ideal_balance = D1 * old_balances[i] / D0 new_balance = new_balances[i] # unsafe math is safu here: if ideal_balance > new_balance: difference = unsafe_sub(ideal_balance, new_balance) else: difference = unsafe_sub(new_balance, ideal_balance) # fee[i] = _dynamic_fee(i, j) * difference / FEE_DENOMINATOR xs = unsafe_div(rates[i] * (old_balances[i] + new_balance), PRECISION) _dynamic_fee_i = self._dynamic_fee(xs, ys, base_fee) fees.append( unsafe_div( _dynamic_fee_i * difference, FEE_DENOMINATOR ) ) # fees[i] * admin_fee / FEE_DENOMINATOR self.admin_balances[i] += unsafe_div(fees[i] * admin_fee, FEE_DENOMINATOR) new_balances[i] -= fees[i] xp: DynArray[uint256, MAX_COINS] = self._xp_mem(rates, new_balances) D1 = math.get_D(xp, amp, N_COINS) # <------ Reuse D1 for new D value. mint_amount = total_supply * (D1 - D0) / D0 self.upkeep_oracles(xp, amp, D1) else: mint_amount = D1 # Take the dust if there was any # (re)instantiate D oracle if totalSupply is zero. self.last_D_packed = self.pack_2(D1, D1) assert mint_amount >= _min_mint_amount, "Slippage screwed you" # Mint pool tokens total_supply += mint_amount self.balanceOf[_receiver] += mint_amount self.total_supply = total_supply log Transfer(empty(address), _receiver, mint_amount) log AddLiquidity(msg.sender, _amounts, fees, D1, total_supply) return mint_amount ``` ```shell >>> StableSwap.get_balances() [4183467888075, 2556883713184291687567176] >>> StableSwap.add_liquidity([10**6, 0], 0) 9992841836391963157 >>> StableSwap.get_balances() [4183477887978, 2556883713089250297597078] ``` :::: ### `remove_liquidity` ::::description[`StableSwap.remove_liquidity(_burn_amount: uint256, _min_amounts: DynArray[uint256, MAX_COINS], _receiver: address = msg.sender, _claim_admin_fees: bool = True) -> DynArray[uint256, MAX_COINS]:`] :::info When removing liquidity in a balanced ratio, there is no need to update the price oracle, as this function does not alter the balance ratio within the pool. Calling this function only updates `D_oracle`. The calculation of `D` does not use Newton methods, ensuring that `remove_liquidity` should always work, even if the pool gets borked. ::: Function to remove `_min_amount` coins from the liquidity pool based on the pools current ratios by burning `_burn_amount` of LP tokens. Admin fees might be claimed after liquidity is removed. Returns: amount of coins withdrawn (`DynArray[uint256, MAX_COINS]`). Emits: `RemoveLiquidity` | Input | Type | Description | | ------------------ | ------------------------------ | -------------------------------------------------- | | `_burn_amount` | `uint256` | Amount of LP tokens to be burned. | | `_min_amounts` | `DynArray[uint256, MAX_COINS]` | Minimum amounts of coins to receive. | | `_receiver` | `address` | Receiver of the coins; defaults to `msg.sender`. | | `_claim_admin_fees`| `bool` | If admin fees should be claimed; defaults to `true`.| ```vyper event RemoveLiquidity: provider: indexed(address) token_amounts: DynArray[uint256, MAX_COINS] fees: DynArray[uint256, MAX_COINS] token_supply: uint256 @external @nonreentrant('lock') def remove_liquidity( _burn_amount: uint256, _min_amounts: DynArray[uint256, MAX_COINS], _receiver: address = msg.sender, _claim_admin_fees: bool = True, ) -> DynArray[uint256, MAX_COINS]: """ @notice Withdraw coins from the pool @dev Withdrawal amounts are based on current deposit ratios @param _burn_amount Quantity of LP tokens to burn in the withdrawal @param _min_amounts Minimum amounts of underlying coins to receive @param _receiver Address that receives the withdrawn coins @return List of amounts of coins that were withdrawn """ total_supply: uint256 = self.total_supply assert _burn_amount > 0 # dev: invalid _burn_amount amounts: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances: DynArray[uint256, MAX_COINS] = self._balances() value: uint256 = 0 for i in range(N_COINS_128): value = unsafe_div(balances[i] * _burn_amount, total_supply) assert value >= _min_amounts[i], "Withdrawal resulted in fewer coins than expected" amounts.append(value) self._transfer_out(i, value, _receiver) self._burnFrom(msg.sender, _burn_amount) # dev: insufficient funds # --------------------------- Upkeep D_oracle ---------------------------- ma_last_time_unpacked: uint256[2] = self.unpack_2(self.ma_last_time) last_D_packed_current: uint256 = self.last_D_packed old_D: uint256 = last_D_packed_current & (2**128 - 1) self.last_D_packed = self.pack_2( old_D - unsafe_div(old_D * _burn_amount, total_supply), # new_D = proportionally reduce D. self._calc_moving_average( last_D_packed_current, self.D_ma_time, ma_last_time_unpacked[1] ) ) if ma_last_time_unpacked[1] < block.timestamp: ma_last_time_unpacked[1] = block.timestamp self.ma_last_time = self.pack_2(ma_last_time_unpacked[0], ma_last_time_unpacked[1]) # ------------------------------- Log event ------------------------------ log RemoveLiquidity( msg.sender, amounts, empty(DynArray[uint256, MAX_COINS]), total_supply - _burn_amount ) # ------- Withdraw admin fees if _claim_admin_fees is set to True -------- if _claim_admin_fees: self._withdraw_admin_fees() return amounts ``` ```shell >>> StableSwap.get_balances() [4183477887978, 2556883713089250297628878] >>> StableSwap.remove_liquidity(10**18, [0, 0]) 614190, 375384835097322069 >>> StableSwap.get_balances() [4183477273788, 2556883337704415200306809] ``` :::: ### `remove_liquidity_one_coin` ::::description[`StableSwap.remove_liquidity_one_coin(_burn_amount: uint256, i: int128, _min_received: uint256, _receiver: address = msg.sender) -> uint256:`] Function to remove a minimum of `_min_received` of coin `i` by burning `_burn_amount` of LP tokens. Returns: coins received (`uint256`). Emits: `RemoveLiquidityOne` | Input | Type | Description | | --------------- | ---------- | -------------------------------------------------- | | `_burn_amount` | `uint256` | Amount of LP tokens to burn/withdraw. | | `i` | `int128` | Index value of the coin to withdraw. | | `_min_received`| `uint256` | Minimum amount of coin to receive. | | `_receiver` | `address` | Receiver of the coins; defaults to `msg.sender`. | ```vyper event RemoveLiquidityOne: provider: indexed(address) token_id: int128 token_amount: uint256 coin_amount: uint256 token_supply: uint256 @external @nonreentrant('lock') def remove_liquidity_one_coin( _burn_amount: uint256, i: int128, _min_received: uint256, _receiver: address = msg.sender, ) -> uint256: """ @notice Withdraw a single coin from the pool @param _burn_amount Amount of LP tokens to burn in the withdrawal @param i Index value of the coin to withdraw @param _min_received Minimum amount of coin to receive @param _receiver Address that receives the withdrawn coins @return Amount of coin received """ assert _burn_amount > 0 # dev: do not remove 0 LP tokens dy: uint256 = 0 fee: uint256 = 0 xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) amp: uint256 = empty(uint256) D: uint256 = empty(uint256) dy, fee, xp, amp, D = self._calc_withdraw_one_coin(_burn_amount, i) assert dy >= _min_received, "Not enough coins removed" # fee * admin_fee / FEE_DENOMINATOR self.admin_balances[i] += unsafe_div(fee * admin_fee, FEE_DENOMINATOR) self._burnFrom(msg.sender, _burn_amount) log Transfer(msg.sender, empty(address), _burn_amount) self._transfer_out(i, dy, _receiver) log RemoveLiquidityOne(msg.sender, i, _burn_amount, dy, self.total_supply) self.upkeep_oracles(xp, amp, D) return dy @view @internal def _calc_withdraw_one_coin( _burn_amount: uint256, i: int128 ) -> ( uint256, uint256, DynArray[uint256, MAX_COINS], uint256, uint256 ): # First, need to: # * Get current D # * Solve Eqn against y_i for D - _token_amount # get pool state amp: uint256 = self._A() rates: DynArray[uint256, MAX_COINS] = self._stored_rates() xp: DynArray[uint256, MAX_COINS] = self._xp_mem(rates, self._balances()) D0: uint256 = math.get_D(xp, amp, N_COINS) total_supply: uint256 = self.total_supply D1: uint256 = D0 - _burn_amount * D0 / total_supply new_y: uint256 = math.get_y_D(amp, i, xp, D1, N_COINS) xp_reduced: DynArray[uint256, MAX_COINS] = xp ys: uint256 = (D0 + D1) / (2 * N_COINS) base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1)) dx_expected: uint256 = 0 xp_j: uint256 = 0 xavg: uint256 = 0 dynamic_fee: uint256 = 0 for j in range(N_COINS_128): dx_expected = 0 xp_j = xp[j] if j == i: dx_expected = xp_j * D1 / D0 - new_y xavg = (xp_j + new_y) / 2 else: dx_expected = xp_j - xp_j * D1 / D0 xavg = xp_j # xp_j - dynamic_fee * dx_expected / FEE_DENOMINATOR dynamic_fee = self._dynamic_fee(xavg, ys, base_fee) xp_reduced[j] = xp_j - unsafe_div(dynamic_fee * dx_expected, FEE_DENOMINATOR) dy: uint256 = xp_reduced[i] - math.get_y_D(amp, i, xp_reduced, D1, N_COINS) dy_0: uint256 = (xp[i] - new_y) * PRECISION / rates[i] # w/o fees dy = (dy - 1) * PRECISION / rates[i] # Withdraw less to account for rounding errors # calculate state price xp[i] = new_y return dy, dy_0 - dy, xp, amp, D1 ``` ```shell >>> StableSwap.remove_liquidity_one_coin(10**18, 0, 0) 1000638 >>> StableSwap.remove_liquidity_one_coin(10**18, 1, 0) 971872609646322618 ``` :::: ### `remove_liquidity_imbalance` ::::description[`StableSwap.remove_liquidity_imbalance(_amounts: DynArray[uint256, MAX_COINS], _max_burn_amount: uint256, _receiver: address = msg.sender) -> uint256:`] Function to burn a maximum of `_max_burn_amount` of LP tokens in order to receive `_amounts` of underlying tokens. Returns: amount of LP tokens burned (`uint256`). Emits: `RemoveLiquidityImbalance` | Input | Type | Description | | ------------------ | ------------------------------ | -------------------------------------------------- | | `_amounts` | `DynArray[uint256, MAX_COINS]`| List of amounts of coins to withdraw. | | `_max_burn_amount` | `uint256` | Maximum amount of LP tokens to burn. | | `_receiver` | `address` | Receiver of the coins; defaults to `msg.sender`. | ```vyper event RemoveLiquidityImbalance: provider: indexed(address) token_amounts: DynArray[uint256, MAX_COINS] fees: DynArray[uint256, MAX_COINS] invariant: uint256 token_supply: uint256 @external @nonreentrant('lock') def remove_liquidity_imbalance( _amounts: DynArray[uint256, MAX_COINS], _max_burn_amount: uint256, _receiver: address = msg.sender ) -> uint256: """ @notice Withdraw coins from the pool in an imbalanced amount @param _amounts List of amounts of underlying coins to withdraw @param _max_burn_amount Maximum amount of LP token to burn in the withdrawal @param _receiver Address that receives the withdrawn coins @return Actual amount of the LP token burned in the withdrawal """ amp: uint256 = self._A() rates: DynArray[uint256, MAX_COINS] = self._stored_rates() old_balances: DynArray[uint256, MAX_COINS] = self._balances() D0: uint256 = self.get_D_mem(rates, old_balances, amp) new_balances: DynArray[uint256, MAX_COINS] = old_balances for i in range(N_COINS_128): if _amounts[i] != 0: new_balances[i] -= _amounts[i] self._transfer_out(i, _amounts[i], _receiver) D1: uint256 = self.get_D_mem(rates, new_balances, amp) base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1)) ys: uint256 = (D0 + D1) / N_COINS fees: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) dynamic_fee: uint256 = 0 xs: uint256 = 0 ideal_balance: uint256 = 0 difference: uint256 = 0 new_balance: uint256 = 0 for i in range(N_COINS_128): ideal_balance = D1 * old_balances[i] / D0 new_balance = new_balances[i] if ideal_balance > new_balance: difference = ideal_balance - new_balance else: difference = new_balance - ideal_balance # base_fee * difference / FEE_DENOMINATOR xs = unsafe_div(rates[i] * (old_balances[i] + new_balance), PRECISION) dynamic_fee = self._dynamic_fee(xs, ys, base_fee) fees.append(unsafe_div(dynamic_fee * difference, FEE_DENOMINATOR)) # fees[i] * admin_fee / FEE_DENOMINATOR self.admin_balances[i] += unsafe_div(fees[i] * admin_fee, FEE_DENOMINATOR) new_balances[i] -= fees[i] D1 = self.get_D_mem(rates, new_balances, amp) # dev: reuse D1 for new D. self.upkeep_oracles(self._xp_mem(rates, new_balances), amp, D1) total_supply: uint256 = self.total_supply burn_amount: uint256 = ((D0 - D1) * total_supply / D0) + 1 assert burn_amount > 1 # dev: zero tokens burned assert burn_amount <= _max_burn_amount, "Slippage screwed you" self._burnFrom(msg.sender, burn_amount) log RemoveLiquidityImbalance(msg.sender, _amounts, fees, D1, total_supply) return burn_amount ``` ```shell >>> StableSwap.remove_liquidity_imbalance([2000000, 10**18], 50**18) 3027537955031682593 ``` :::note This method removes liquidity in an imbalanced portion (2 USDV and one 3CRV) by burning a `burn_amount` of LP tokens (3027537955031682593). ::: :::: ### `calc_token_amount` ::::description[`StableSwap.calc_token_amount(_amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool) -> uint256:`] Function to calculate the addition or reduction of token supply from a deposit (add liquidity) or withdrawal (remove liquidity). This function does take fees into consideration. Returns: amount of LP tokens (`uint256`). | Input | Type | Description | | -------------- | ------------------------------ | -------------------------------------------------- | | `_amounts` | `DynArray[uint256, MAX_COINS]` | Amount of coins being deposited/withdrawn. | | `_is_deposit` | `bool` | `true` = deposit, `false` = withdraw. | ```vyper interface StableSwapViews: def get_dx(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def get_dx_underlying(i: int128, j: int128, dy: uint256, pool: address) -> uint256: view def get_dy_underlying(i: int128, j: int128, dx: uint256, pool: address) -> uint256: view def dynamic_fee(i: int128, j: int128, pool: address) -> uint256: view def calc_token_amount( _amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool, _pool: address ) -> uint256: view @view @external def calc_token_amount( _amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool ) -> uint256: """ @notice Calculate addition or reduction in token supply from a deposit or withdrawal @param _amounts Amount of each coin being deposited @param _is_deposit set True for deposits, False for withdrawals @return Expected amount of LP tokens received """ return StableSwapViews(factory.views_implementation()).calc_token_amount(_amounts, _is_deposit, self) ``` ```vyper @view @external def calc_token_amount( _amounts: DynArray[uint256, MAX_COINS], _is_deposit: bool, pool: address ) -> uint256: """ @notice Calculate addition or reduction in token supply from a deposit or withdrawal @param _amounts Amount of each coin being deposited @param _is_deposit set True for deposits, False for withdrawals @return Expected amount of LP tokens received """ amp: uint256 = StableSwapNG(pool).A() * A_PRECISION N_COINS: uint256 = StableSwapNG(pool).N_COINS() rates: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) old_balances: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) rates, old_balances, xp = self._get_rates_balances_xp(pool, N_COINS) # Initial invariant D0: uint256 = self.get_D(xp, amp, N_COINS) total_supply: uint256 = StableSwapNG(pool).totalSupply() new_balances: DynArray[uint256, MAX_COINS] = old_balances for i in range(MAX_COINS): if i == N_COINS: break amount: uint256 = _amounts[i] if _is_deposit: new_balances[i] += amount else: new_balances[i] -= amount # Invariant after change for idx in range(MAX_COINS): if idx == N_COINS: break xp[idx] = rates[idx] * new_balances[idx] / PRECISION D1: uint256 = self.get_D(xp, amp, N_COINS) # We need to recalculate the invariant accounting for fees # to calculate fair user's share D2: uint256 = D1 if total_supply > 0: # Only account for fees if we are not the first to deposit base_fee: uint256 = StableSwapNG(pool).fee() * N_COINS / (4 * (N_COINS - 1)) fee_multiplier: uint256 = StableSwapNG(pool).offpeg_fee_multiplier() _dynamic_fee_i: uint256 = 0 xs: uint256 = 0 ys: uint256 = (D0 + D1) / N_COINS for i in range(MAX_COINS): if i == N_COINS: break ideal_balance: uint256 = D1 * old_balances[i] / D0 difference: uint256 = 0 new_balance: uint256 = new_balances[i] if ideal_balance > new_balance: difference = ideal_balance - new_balance else: difference = new_balance - ideal_balance xs = old_balances[i] + new_balance _dynamic_fee_i = self._dynamic_fee(xs, ys, base_fee, fee_multiplier) new_balances[i] -= _dynamic_fee_i * difference / FEE_DENOMINATOR for idx in range(MAX_COINS): if idx == N_COINS: break xp[idx] = rates[idx] * new_balances[idx] / PRECISION D2 = self.get_D(xp, amp, N_COINS) else: return D1 # Take the dust if there was any diff: uint256 = 0 if _is_deposit: diff = D2 - D0 else: diff = D0 - D2 return diff * total_supply / D0 ``` ```shell >>> StableSwap.calc_token_amount([10**6, 10**18], False) 2028274156743388789 ``` :::: ### `calc_withdraw_one_coin` ::::description[`StableSwap.calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256:`] Function to calculate the amount of single token `i` withdrawn when burning `_burn_amount` LP tokens. Returns: amount of tokens withdrawn (`uint256`). | Input | Type | Description | | --------------- | --------- | -------------------------------------------------- | | `_burn_amount` | `uint256` | Amount of LP tokens to burn. | | `i` | `int128` | Index value of the coin to withdraw. | ```vyper @view @external def calc_withdraw_one_coin(_burn_amount: uint256, i: int128) -> uint256: """ @notice Calculate the amount received when withdrawing a single coin @param _burn_amount Amount of LP tokens to burn in the withdrawal @param i Index value of the coin to withdraw @return Amount of coin received """ return self._calc_withdraw_one_coin(_burn_amount, i)[0] @view @internal def _calc_withdraw_one_coin( _burn_amount: uint256, i: int128 ) -> ( uint256, uint256, DynArray[uint256, MAX_COINS], uint256, uint256 ): # First, need to: # * Get current D # * Solve Eqn against y_i for D - _token_amount # get pool state amp: uint256 = self._A() rates: DynArray[uint256, MAX_COINS] = self._stored_rates() xp: DynArray[uint256, MAX_COINS] = self._xp_mem(rates, self._balances()) D0: uint256 = math.get_D(xp, amp, N_COINS) total_supply: uint256 = self.total_supply D1: uint256 = D0 - _burn_amount * D0 / total_supply new_y: uint256 = math.get_y_D(amp, i, xp, D1, N_COINS) xp_reduced: DynArray[uint256, MAX_COINS] = xp ys: uint256 = (D0 + D1) / (2 * N_COINS) base_fee: uint256 = self.fee * N_COINS / (4 * (N_COINS - 1)) dx_expected: uint256 = 0 xp_j: uint256 = 0 xavg: uint256 = 0 dynamic_fee: uint256 = 0 for j in range(N_COINS_128): dx_expected = 0 xp_j = xp[j] if j == i: dx_expected = xp_j * D1 / D0 - new_y xavg = (xp_j + new_y) / 2 else: dx_expected = xp_j - xp_j * D1 / D0 xavg = xp_j # xp_j - dynamic_fee * dx_expected / FEE_DENOMINATOR dynamic_fee = self._dynamic_fee(xavg, ys, base_fee) xp_reduced[j] = xp_j - unsafe_div(dynamic_fee * dx_expected, FEE_DENOMINATOR) dy: uint256 = xp_reduced[i] - math.get_y_D(amp, i, xp_reduced, D1, N_COINS) dy_0: uint256 = (xp[i] - new_y) * PRECISION / rates[i] # w/o fees dy = (dy - 1) * PRECISION / rates[i] # Withdraw less to account for rounding errors # calculate state price xp[i] = new_y return dy, dy_0 - dy, xp, amp, D1 ``` ```shell >>> StableSwap.calc_withdraw_one_coin(10**18, 0) 1000638 >>> StableSwap.calc_withdraw_one_coin(10**18, 1) 971872610064262793 >>> StableSwap.get_balances() [4183467888075, 2556883713184291687567176] # [coin[0], coin[1]] ``` :::: --- ## Fee Methods Stableswap-ng introduces a dynamic fee based on the imbalance of the coins within the pool and their pegs: ```vyper offpeg_fee_multiplier: public(uint256) # * 1e10 @view @internal def _dynamic_fee(xpi: uint256, xpj: uint256, _fee: uint256) -> uint256: _offpeg_fee_multiplier: uint256 = self.offpeg_fee_multiplier if _offpeg_fee_multiplier <= FEE_DENOMINATOR: return _fee xps2: uint256 = (xpi + xpj) **2 return ( (_offpeg_fee_multiplier * _fee) / ((_offpeg_fee_multiplier - FEE_DENOMINATOR) * 4 * xpi * xpj / xps2 + FEE_DENOMINATOR) ) ``` More on dynamic fees [here](../overview.md#dynamic-fees). ### `fee` ::::description[`StableSwap.fee() -> uint256: view`] Getter method for the fee of the pool. The fee is expressed as an integer with a 1e10 precision. This is the value set when initializing the contract and can be changed via [`set_new_fee`](#set_new_fee). Returns: fee (`uint256`). ```vyper fee: public(uint256) # fee * 1e10 @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _math_implementation: address, _base_pool: address, _coins: DynArray[address, MAX_COINS], _base_coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... self.fee = _fee ... ``` ```shell >>> StableSwap.fee() 1000000 ``` :::note The method returns an integer with with 1e10 precision. ::: :::: ### `dynamic_fee` ::::description[`StableSwap.dynamic_fee(i: int128, j: int128) -> uint256:`] Getter for the swap fee when exchanging between `i` and `j`. The swap fee is expressed as an integer with a 1e10 precision. Returns: dynamic fee (`uint256`). | Input | Type | Description | | ------ | -------- | ------------------------------------------ | | `i` | `int128` | Index value of input coin. | | `j` | `int128` | Index value of output coin. | ```vyper @view @external def dynamic_fee(i: int128, j: int128) -> uint256: """ @notice Return the fee for swapping between `i` and `j` @param i Index value for the coin to send @param j Index value of the coin to recieve @return Swap fee expressed as an integer with 1e10 precision """ return StableSwapViews(factory.views_implementation()).dynamic_fee(i, j, self) ``` ```vyper @view @external def dynamic_fee(i: int128, j: int128, pool:address) -> uint256: """ @notice Return the fee for swapping between `i` and `j` @param i Index value for the coin to send @param j Index value of the coin to recieve @return Swap fee expressed as an integer with 1e10 precision """ N_COINS: uint256 = StableSwapNG(pool).N_COINS() fee: uint256 = StableSwapNG(pool).fee() fee_multiplier: uint256 = StableSwapNG(pool).offpeg_fee_multiplier() rates: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) rates, balances, xp = self._get_rates_balances_xp(pool, N_COINS) return self._dynamic_fee(xp[i], xp[j], fee, fee_multiplier) @view @internal def _dynamic_fee(xpi: uint256, xpj: uint256, _fee: uint256, _fee_multiplier: uint256) -> uint256: if _fee_multiplier <= FEE_DENOMINATOR: return _fee xps2: uint256 = (xpi + xpj) **2 return ( (_fee_multiplier * _fee) / ((_fee_multiplier - FEE_DENOMINATOR) * 4 * xpi * xpj / xps2 + FEE_DENOMINATOR) ) @view @internal def _get_rates_balances_xp(pool: address, N_COINS: uint256) -> ( DynArray[uint256, MAX_COINS], DynArray[uint256, MAX_COINS], DynArray[uint256, MAX_COINS], ): rates: DynArray[uint256, MAX_COINS] = StableSwapNG(pool).stored_rates() balances: DynArray[uint256, MAX_COINS] = StableSwapNG(pool).get_balances() xp: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) for idx in range(MAX_COINS): if idx == N_COINS: break xp.append(rates[idx] * balances[idx] / PRECISION) return rates, balances, xp ``` ```shell >>> StableSwap.dynamic_fee(0, 1) 1043403 ``` :::note The method returns an integer with with 1e10 precision. ::: :::: ### `admin_fee` ::::description[`StableSwap.admin_fee() -> uint256: view`] Getter for the admin fee. It is a constant and is set to 50% (5000000000). Returns: admin fee (`uint256`). ```vyper admin_fee: public(constant(uint256)) = 5000000000 ``` ```shell >>> StableSwap.admin_fee() 5000000000 ``` :::note The method returns an integer with with 1e10 precision. ::: :::: ### `offpeg_fee_multiplier` ::::description[`StableSwap.offpeg_fee_multiplier() -> uint256: view`] Getter method for the off-peg fee multiplier. This value determines how much the fee increases when assets within the AMM depeg. This value can be changed via [`set_new_fee`](#set_new_fee). Returns: offpeg fee multiplier (`uint256`) ```vyper offpeg_fee_multiplier: public(uint256) # * 1e10 @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _math_implementation: address, _base_pool: address, _coins: DynArray[address, MAX_COINS], _base_coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... self.offpeg_fee_multiplier = _offpeg_fee_multiplier ... ``` ```shell >>> StableSwap.offpeg_fee_multiplier() 50000000000 ``` :::note The method returns an integer with with 1e10 precision. ::: :::: ### `stored_rates` ::::description[`StableSwap.stored_rates() -> DynArray[uint256, MAX_COINS]:`view] Getter for the rate multiplier of each coin. Returns: stored rates (`DynArray[uint256, MAX_COINS]`). :::info If the coin has a rate oracle that has been properly initialized, this method queries that rate by static-calling an external contract. ::: ```vyper rate_multipliers: immutable(DynArray[uint256, MAX_COINS]) # [bytes4 method_id][bytes8 ][bytes20 oracle] oracles: DynArray[uint256, MAX_COINS] @view @external def stored_rates() -> DynArray[uint256, MAX_COINS]: return self._stored_rates() @view @internal def _stored_rates() -> DynArray[uint256, MAX_COINS]: """ @notice Gets rate multipliers for each coin. @dev If the coin has a rate oracle that has been properly initialised, this method queries that rate by static-calling an external contract. """ rates: DynArray[uint256, MAX_COINS] = [ rate_multipliers[0], StableSwap(BASE_POOL).get_virtual_price() ] oracles: DynArray[uint256, MAX_COINS] = self.oracles if not self.oracles[0] == 0: response: Bytes[32] = raw_call( convert(oracles[0] % 2**160, address), _abi_encode(oracles[0] & ORACLE_BIT_MASK), max_outsize=32, is_static_call=True, ) # rates[0] * convert(response, uint256) / PRECISION rates[0] = unsafe_div(rates[0] * convert(response, uint256), PRECISION) return rates ``` ```shell >>> StableSwap.stored_rates() [1000000000000000000000000000000, 1028532570390672122] ``` :::: ### `admin_balances` ::::description[`StableSwap.admin_balances(arg0: uint256) -> uint256: view`] Getter for the accumulated admin balance of the pool for a coin. These values essentially represent the claimable admin fee. Returns: admin balances (`uint256`). | Input | Type | Description | | ------ | --------- | ------------------------------------------ | | `arg0` | `uint256` | Index value of the coin. | ```vyper admin_balances: public(DynArray[uint256, MAX_COINS]) ``` ```shell >>> StableSwap.admin_balances(0) 73146476 >>> StableSwap.admin_balances(1) 129624596387098161946 ``` :::: ### `withdraw_admin_fees` ::::description[`StableSwap.withdraw_admin_fees():`] Function to withdraw accumulated admin fees from the pool and send them to the `fee_receiver` set within the Factory. ```vyper interface Factory: def fee_receiver() -> address: view def admin() -> address: view def views_implementation() -> address: view admin_balances: public(DynArray[uint256, MAX_COINS]) @external def withdraw_admin_fees(): """ @notice Claim admin fees. Callable by anyone. """ self._withdraw_admin_fees() @internal def _withdraw_admin_fees(): fee_receiver: address = factory.fee_receiver() assert fee_receiver != empty(address) # dev: fee receiver not set admin_balances: DynArray[uint256, MAX_COINS] = self.admin_balances for i in range(N_COINS_128): if admin_balances[i] > 0: self._transfer_out(i, admin_balances[i], fee_receiver) admin_balances[i] = 0 self.admin_balances = admin_balances ``` ```shell >>> StableSwap.withdraw_admin_fees() ``` :::: --- ## Amplification Coefficient The amplification coefficient **`A`**determines a pool’s tolerance for imbalance between the assets within it. A higher value means that trades will incur slippage sooner as the assets within the pool become imbalanced. The appropriate value for A is dependent upon the type of coin being used within the pool, and is subject to optimisation. It is possible to modify the amplification coefficient for a pool via the **`ramp_A`**function. See [admin controls](#ramp_a). When a ramping of A has been initialized, the process can be stopped by calling the function [**`stop_ramp_A()`**](#stop_ramp_a). ### `A` ::::description[`StableSwap.A() -> uint256: view`] Getter for the amplification coefficient A. Returns: A (`uint256`). ```vyper A_PRECISION: constant(uint256) = 100 MAX_A: constant(uint256) = 10 **6 MAX_A_CHANGE: constant(uint256) = 10 initial_A: public(uint256) future_A: public(uint256) initial_A_time: public(uint256) future_A_time: public(uint256) @view @external def A() -> uint256: return unsafe_div(self._A(), A_PRECISION) @view @internal def _A() -> uint256: """ Handle ramping A up or down """ t1: uint256 = self.future_A_time A1: uint256 = self.future_A if block.timestamp < t1: A0: uint256 = self.initial_A t0: uint256 = self.initial_A_time # Expressions in uint256 cannot have negative numbers, thus "if" if A1 > A0: return A0 + (A1 - A0) * (block.timestamp - t0) / (t1 - t0) else: return A0 - (A0 - A1) * (block.timestamp - t0) / (t1 - t0) else: # when t1 == 0 or block.timestamp >= t1 return A1 ``` ```shell >>> StableSwap.A() 500 ``` :::note The amplification coefficient is scaled by `A_precise`. ::: :::: ### `A_precise` ::::description[`StableSwap.A_precise() -> uint256: view`] Getter for the precise A value, which is not divided by `A_precise` unlike `A`. Returns: precise A (`uint256`). ```vyper A_PRECISION: constant(uint256) = 100 MAX_A: constant(uint256) = 10 **6 MAX_A_CHANGE: constant(uint256) = 10 initial_A: public(uint256) future_A: public(uint256) initial_A_time: public(uint256) future_A_time: public(uint256) @view @external def A_precise() -> uint256: return self._A() ``` ```shell >>> StableSwap.A_precise() 50000 ``` :::: ### `initial_A` ::::description[`StableSwap.initial_A() -> uint256: view`] Getter for the initial A value. This is the A value when the ramping was initialized. Returns: initial A (`uint256`). ```vyper A_PRECISION: constant(uint256) = 100 MAX_A: constant(uint256) = 10 **6 MAX_A_CHANGE: constant(uint256) = 10 initial_A: public(uint256) future_A: public(uint256) initial_A_time: public(uint256) future_A_time: public(uint256) @external def ramp_A(_future_A: uint256, _future_time: uint256): assert msg.sender == factory.admin() # dev: only owner assert block.timestamp >= self.initial_A_time + MIN_RAMP_TIME assert _future_time >= block.timestamp + MIN_RAMP_TIME # dev: insufficient time _initial_A: uint256 = self._A() _future_A_p: uint256 = _future_A * A_PRECISION assert _future_A > 0 and _future_A < MAX_A if _future_A_p < _initial_A: assert _future_A_p * MAX_A_CHANGE >= _initial_A else: assert _future_A_p <= _initial_A * MAX_A_CHANGE self.initial_A = _initial_A self.future_A = _future_A_p self.initial_A_time = block.timestamp self.future_A_time = _future_time log RampA(_initial_A, _future_A_p, block.timestamp, _future_time) ``` ```shell >>> StableSwap.initial_A() 500 ``` :::: ### `future_A` ::::description[`StableSwap.future_A() -> uint256: view`] Getter for the future A value. This value is adjusted when ramping A. Returns: future A (`uint256`). ```vyper A_PRECISION: constant(uint256) = 100 MAX_A: constant(uint256) = 10 **6 MAX_A_CHANGE: constant(uint256) = 10 initial_A: public(uint256) future_A: public(uint256) initial_A_time: public(uint256) future_A_time: public(uint256) @external def ramp_A(_future_A: uint256, _future_time: uint256): assert msg.sender == factory.admin() # dev: only owner assert block.timestamp >= self.initial_A_time + MIN_RAMP_TIME assert _future_time >= block.timestamp + MIN_RAMP_TIME # dev: insufficient time _initial_A: uint256 = self._A() _future_A_p: uint256 = _future_A * A_PRECISION assert _future_A > 0 and _future_A < MAX_A if _future_A_p < _initial_A: assert _future_A_p * MAX_A_CHANGE >= _initial_A else: assert _future_A_p <= _initial_A * MAX_A_CHANGE self.initial_A = _initial_A self.future_A = _future_A_p self.initial_A_time = block.timestamp self.future_A_time = _future_time log RampA(_initial_A, _future_A_p, block.timestamp, _future_time) ``` ```shell >>> StableSwap.future_A() 500 ``` :::: ### `initial_A_time` ::::description[`StableSwap.initial_A_time() -> uint256: view`] Getter for the initial A time. This is the timestamp when ramping A was initialized. Returns: initial A time (`uint256`). ```vyper A_PRECISION: constant(uint256) = 100 MAX_A: constant(uint256) = 10 **6 MAX_A_CHANGE: constant(uint256) = 10 initial_A: public(uint256) future_A: public(uint256) initial_A_time: public(uint256) future_A_time: public(uint256) @external def ramp_A(_future_A: uint256, _future_time: uint256): assert msg.sender == factory.admin() # dev: only owner assert block.timestamp >= self.initial_A_time + MIN_RAMP_TIME assert _future_time >= block.timestamp + MIN_RAMP_TIME # dev: insufficient time _initial_A: uint256 = self._A() _future_A_p: uint256 = _future_A * A_PRECISION assert _future_A > 0 and _future_A < MAX_A if _future_A_p < _initial_A: assert _future_A_p * MAX_A_CHANGE >= _initial_A else: assert _future_A_p <= _initial_A * MAX_A_CHANGE self.initial_A = _initial_A self.future_A = _future_A_p self.initial_A_time = block.timestamp self.future_A_time = _future_time log RampA(_initial_A, _future_A_p, block.timestamp, _future_time) ``` ```shell >>> StableSwap.initial_A_time() 0 ``` :::: ### `future_A_time` ::::description[`StableSwap.future_A_time() -> uint256: view`] Getter for the future A time. This is the timestamp when ramping A should be finished. Returns: future A time (`uint256`). ```vyper A_PRECISION: constant(uint256) = 100 MAX_A: constant(uint256) = 10 **6 MAX_A_CHANGE: constant(uint256) = 10 initial_A: public(uint256) future_A: public(uint256) initial_A_time: public(uint256) future_A_time: public(uint256) @external def ramp_A(_future_A: uint256, _future_time: uint256): assert msg.sender == factory.admin() # dev: only owner assert block.timestamp >= self.initial_A_time + MIN_RAMP_TIME assert _future_time >= block.timestamp + MIN_RAMP_TIME # dev: insufficient time _initial_A: uint256 = self._A() _future_A_p: uint256 = _future_A * A_PRECISION assert _future_A > 0 and _future_A < MAX_A if _future_A_p < _initial_A: assert _future_A_p * MAX_A_CHANGE >= _initial_A else: assert _future_A_p <= _initial_A * MAX_A_CHANGE self.initial_A = _initial_A self.future_A = _future_A_p self.initial_A_time = block.timestamp self.future_A_time = _future_time log RampA(_initial_A, _future_A_p, block.timestamp, _future_time) ``` ```shell >>> StableSwap.future_A_time() 0 ``` :::: --- ## Contract Info Methods ### `BASE_POOL` ::::description[`StableSwap.BASE_POOL() -> address: view`] Getter for the base pool. Returns: base pool (`address`). ```vyper BASE_POOL: public(immutable(address)) @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _math_implementation: address, _base_pool: address, _coins: DynArray[address, MAX_COINS], _base_coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... BASE_POOL = _base_pool ... ``` ```shell >>> StableSwap.BASE_POOL() '0xbEbc44782C7dB0a1A60Cb6fe97d0b483032FF1C7' ``` :::: ### `BASE_N_COINS` ::::description[`StableSwap.BASE_N_COINS() -> uint256: view`] Getter for the number of coins within the base pool. Returns: number of coins (`uint256`). ```vyper MAX_COINS: constant(uint256) = 8 # max coins is 8 in the factory BASE_N_COINS: public(immutable(uint256)) @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _math_implementation: address, _base_pool: address, _coins: DynArray[address, MAX_COINS], _base_coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... BASE_N_COINS = len(_base_coins) ... ``` ```shell >>> StableSwap.BASE_N_COINS() 3 ``` :::: ### `BASE_COINS` ::::description[`StableSwap.BASE_COINS(arg0: uint256) -> address: view`] Getter for the coin at index value `arg0` within the base pool. Returns: coin (`address`). | Input | Type | Description | | ----------- | -------| ----| | `arg0` | `uint256` | Index value of the coin. | ```vyper BASE_COINS: public(immutable(DynArray[address, MAX_COINS])) @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _math_implementation: address, _base_pool: address, _coins: DynArray[address, MAX_COINS], _base_coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... BASE_COINS = _base_coins ... ``` ```shell >>> StableSwap.BASE_COINS(0) '0x6B175474E89094C44Da98b954EedeAC495271d0F' >>> StableSwap.BASE_COINS(1) '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48' >>> StableSwap.BASE_COINS(2) '0xdAC17F958D2ee523a2206206994597C13D831ec7' ``` :::: ### `coins` ::::description[`StableSwap.coins(arg0: uint256) -> addresss: view`] Getter for the coin at index `arg0` within the metapool. coins[0] always return the coin paired against the basepool. Returns: coin (`address`). ```vyper coins: public(immutable(DynArray[address, MAX_COINS])) @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _math_implementation: address, _base_pool: address, _coins: DynArray[address, MAX_COINS], _base_coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... coins = _coins # <---------------- coins[1] is always base pool LP token. ... ``` ```shell >>> StableSwap.coins(0) '0x0E573Ce2736Dd9637A0b21058352e1667925C7a8' >>> StableSwap.coins(1) '0x6c3F90f043a72FA612cbac8115EE7e52BDe6E490' ``` :::note The `coin[0]` is always the metapool token, and `coin[1]` is always the basepool token. ::: :::: ### `balances` ::::description[`StableSwap.balances(i: uint256) -> uint256: view`] Getter for the current balance of coin `i` within the pool. Returns: coin balance (`uint256`). | Input | Type | Description | | ------ | --------- | --------------------------- | | `i` | `uint256` | Index value of the coin. | ```vyper @view @external def balances(i: uint256) -> uint256: """ @notice Get the current balance of a coin within the pool, less the accrued admin fees @param i Index value for the coin to query balance of @return Token balance """ return self._balances()[i] @view @internal def _balances() -> DynArray[uint256, MAX_COINS]: """ @notice Calculates the pool's balances _excluding_ the admin's balances. @dev If the pool contains rebasing tokens, this method ensures LPs keep all rebases and admin only claims swap fees. This also means that, since admin's balances are stored in an array and not inferred from read balances, the fees in the rebasing token that the admin collects is immune to slashing events. """ result: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances_i: uint256 = 0 for i in range(N_COINS_128): if POOL_IS_REBASING_IMPLEMENTATION: balances_i = ERC20(coins[i]).balanceOf(self) - self.admin_balances[i] else: balances_i = self.stored_balances[i] - self.admin_balances[i] result.append(balances_i) return result ``` ```shell >>> StableSwap.balances(0) 4183467888075 >>> StableSwap.balances(1) 2556883713184291687567176 ``` :::: ### `get_balances` ::::description[`StableSwap.get_balances() -> DynArray[uint256, MAX_COINS]: view`] Getter for an array with all coin balances in the pool. Returns: coin balances (`DynArray[uint256, MAX_COINS]`). :::info This getter method does not account for admin fees. ::: ```vyper @view @external def get_balances() -> DynArray[uint256, MAX_COINS]: return self._balances() @view @internal def _balances() -> DynArray[uint256, MAX_COINS]: """ @notice Calculates the pool's balances _excluding_ the admin's balances. @dev If the pool contains rebasing tokens, this method ensures LPs keep all rebases and admin only claims swap fees. This also means that, since admin's balances are stored in an array and not inferred from read balances, the fees in the rebasing token that the admin collects is immune to slashing events. """ result: DynArray[uint256, MAX_COINS] = empty(DynArray[uint256, MAX_COINS]) balances_i: uint256 = 0 for i in range(N_COINS_128): if POOL_IS_REBASING_IMPLEMENTATION: balances_i = ERC20(coins[i]).balanceOf(self) - self.admin_balances[i] else: balances_i = self.stored_balances[i] - self.admin_balances[i] result.append(balances_i) return result ``` ```shell >>> StableSwap.get_balances() [4183467888075, 2556883713184291687567176] ``` :::note The returned values do not take admin fees into account. ::: :::: ### `N_COINS` ::::description[`StableSwap.N_COINS() -> uint256: view`] Getter for the total number of coins in the pool. Returns: number of coins (`uint256`). :::info A metapool always consists of two tokens - basepool token and the token paired against it. ::: ```vyper N_COINS: public(constant(uint256)) = 2 ``` ```shell >>> StableSwap.N_COINS() 2 ``` :::: ### `totalSupply` ::::description[`StableSwap.totalSupply() -> uint256: view`] Getter for the total supply of the LP token. Returns: total supply (`uint256`). ```vyper total_supply: uint256 @view @external @nonreentrant('lock') def totalSupply() -> uint256: """ @notice The total supply of pool LP tokens @return self.total_supply, 18 decimals. """ return self.total_supply ``` ```shell >>> StableSwap.totalSupply() 6811356567627648910003460 ``` :::: --- ## LP Token **Pool and LP tokens are the same smart contract.** The pool itself acts as an LP Token. When coins are deposited into a Curve pool, the depositor receives pool LP (liquidity provider) tokens in return. Each Curve pool has its unique ERC20 contract representing these LP tokens, making them transferable. Holding these LP tokens allows for their deposit and staking in the pool's liquidity gauge, earning CRV token rewards. Additionally, if a metapool supports the LP token, it can be deposited there to receive the metapool's distinct LP tokens. ### `transfer` ::::description[`StableSwap.transfer(_to : address, _value : uint256) -> bool:`] Function to transfer `_value` tokens to `_to`. Returns: true (`bool`). Emits: `Transfer` | Input | Type | Description | | ----------- | -------| ----| | `_to` | `address` | address to transfer token to | | `_value` | `uint256` | amount of tokens to transfer | ```vyper event Transfer: sender: indexed(address) receiver: indexed(address) value: uint256 @external def transfer(_to : address, _value : uint256) -> bool: """ @dev Transfer token for a specified address @param _to The address to transfer to. @param _value The amount to be transferred. """ self._transfer(msg.sender, _to, _value) return True @internal def _transfer(_from: address, _to: address, _value: uint256): # # NOTE: vyper does not allow underflows # # so the following subtraction would revert on insufficient balance self.balanceOf[_from] -= _value self.balanceOf[_to] += _value log Transfer(_from, _to, _value) ``` :::: ### `transferFrom` ::::description[`StableSwap.transferFrom(_from : address, _to : address, _value : uint256) -> bool:`] Function to transfer `_value` tokens from `_from` to `_to`. Returns: true (`bool`). Emits: `Transfer` | Input | Type | Description | | ----------- | -------| ----| | `_from` | `address` | address to transfer token from | | `_to` | `address` | address to transfer token to | | `_value` | `uint256` | amount of tokens to transfer | ```vyper event Transfer: sender: indexed(address) receiver: indexed(address) value: uint256 @external def transferFrom(_from : address, _to : address, _value : uint256) -> bool: """ @dev Transfer tokens from one address to another. @param _from address The address which you want to send tokens from @param _to address The address which you want to transfer to @param _value uint256 the amount of tokens to be transferred """ self._transfer(_from, _to, _value) _allowance: uint256 = self.allowance[_from][msg.sender] if _allowance != max_value(uint256): self.allowance[_from][msg.sender] = _allowance - _value return True @internal def _transfer(_from: address, _to: address, _value: uint256): # # NOTE: vyper does not allow underflows # # so the following subtraction would revert on insufficient balance self.balanceOf[_from] -= _value self.balanceOf[_to] += _value log Transfer(_from, _to, _value) ``` :::: ### `allowance` ::::description[`StableSwap.allowance(arg0: address, arg1: address) -> uint256: view`] Getter method to check the allowance of `arg0` for funds of `arg1`. Returns: allowed amount (`uint256`). | Input | Type | Description | | ----------- | -------| ----| | `arg0` | `address` | Address of the spender | | `arg1` | `address` | Address of the token owner | ```vyper allowance: public(HashMap[address, HashMap[address, uint256]]) ``` :::: ### `approve` ::::description[`StableSwap.approve(_spender : address, _value : uint256) -> bool:`] Function to approve `_spender` to transfer `_value` of tokens on behalf of `msg.sender` Returns: true (`bool`). Emits: `Approval` | Input | Type | Description | |-------------|-----------|---------------------------------| | `_spender` | `address` | Address of the approved spender | | `_value` | `uint256` | Amount of tokens to approve | ```vyper event Approval: owner: indexed(address) spender: indexed(address) value: uint256 @external def approve(_spender : address, _value : uint256) -> bool: """ @notice Approve the passed address to transfer the specified amount of tokens on behalf of msg.sender @dev Beware that changing an allowance via this method brings the risk that someone may use both the old and new allowance by unfortunate transaction ordering: https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729 @param _spender The address which will transfer the funds @param _value The amount of tokens that may be transferred @return bool success """ self.allowance[msg.sender][_spender] = _value log Approval(msg.sender, _spender, _value) return True ``` :::: ### `permit` ::::description[`StableSwap.permit(_owner: address, _spender: address, _value: uint256, _deadline: uint256, _v: uint8, _r: bytes32, _s: bytes32) -> bool:`] Function to permit `spender` to spend up to `_value` amount of `_owner`'s tokens via a signature. Returns: true (`bool`). Emits: `Approval` | Input | Type | Description | | ----------- | -------| ----| | `_owner` | `address` | Account which generated the signature and is granting an allowance | | `_spender` | `address` | Account which will be granted an allowance | | `_value` | `uint256` | Amount to approve | | `_deadline` | `uint256` | Deadline by which signature must be submitted | | `_v` | `uint8` | The last byte of the ECDSA signature | | `_r` | `bytes32` | The first 32 bytes of the ECDSA signature | | `_s` | `bytes32` | The second 32 bytes of the ECDSA signature | ```vyper event Approval: owner: indexed(address) spender: indexed(address) value: uint256 @external def permit( _owner: address, _spender: address, _value: uint256, _deadline: uint256, _v: uint8, _r: bytes32, _s: bytes32 ) -> bool: """ @notice Approves spender by owner's signature to expend owner's tokens. See https://eips.ethereum.org/EIPS/eip-2612. @dev Inspired by https://github.com/yearn/yearn-vaults/blob/main/contracts/Vault.vy#L753-L793 @dev Supports smart contract wallets which implement ERC1271 https://eips.ethereum.org/EIPS/eip-1271 @param _owner The address which is a source of funds and has signed the Permit. @param _spender The address which is allowed to spend the funds. @param _value The amount of tokens to be spent. @param _deadline The timestamp after which the Permit is no longer valid. @param _v The bytes[64] of the valid secp256k1 signature of permit by owner @param _r The bytes[0:32] of the valid secp256k1 signature of permit by owner @param _s The bytes[32:64] of the valid secp256k1 signature of permit by owner @return True, if transaction completes successfully """ assert _owner != empty(address) assert block.timestamp <= _deadline nonce: uint256 = self.nonces[_owner] digest: bytes32 = keccak256( concat( b"\x19\x01", self._domain_separator(), keccak256(_abi_encode(EIP2612_TYPEHASH, _owner, _spender, _value, nonce, _deadline)) ) ) if _owner.is_contract: sig: Bytes[65] = concat(_abi_encode(_r, _s), slice(convert(_v, bytes32), 31, 1)) # reentrancy not a concern since this is a staticcall assert ERC1271(_owner).isValidSignature(digest, sig) == ERC1271_MAGIC_VAL else: assert ecrecover(digest, convert(_v, uint256), convert(_r, uint256), convert(_s, uint256)) == _owner self.allowance[_owner][_spender] = _value self.nonces[_owner] = nonce + 1 log Approval(_owner, _spender, _value) return True ``` :::: ### `name` ::::description[`StableSwap.name() -> String[64]: view`] Getter for the name of the LP token. Returns: name (`String[64]`). ```vyper name: public(immutable(String[64])) @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... name = _name ... ``` ```shell >>> StableSwap.name() 'USDV-crvUSD' ``` :::: ### `symbol` ::::description[`StableSwap.symbol() -> String[32]: view`] Getter for the symbol of the LP token. Returns: symbol (`String[32]`). ```vyper symbol: public(immutable(String[32])) @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... symbol = _symbol ... ``` ```shell >>> StableSwap.symbol() 'USDVcrvUSD' ``` :::: ### `decimals` ::::description[`StableSwap.decimals() -> uint8: view`] Getter for the decimals of the LP token. Returns: decimals (uint8). ```vyper decimals: public(constant(uint8)) = 18 ``` ```shell >>> StableSwap.decimals() 18 ``` :::: ### `version` ::::description[`StableSwap.version() -> String[8]: view`] Getter for the version of the LP token. Returns: version (`String[8]`). ```vyper version: public(constant(String[8])) = "v7.0.0" ``` ```shell >>> StableSwap.version() "v7.0.0" ``` :::: ### `balanceOf` ::::description[`StableSwap.balanceOf(arg0: address) -> uint256: view`] Getter for the LP token balance of `arg0`. Returns: token balance (`uint256`). | Input | Type | Description | | ----------- | -------| ----| | `arg0` | `address` | address to check the balance of | ```vyper balanceOf: public(HashMap[address, uint256]) ``` ```shell >>> StableSwap.balanceOf("0x7a16fF8270133F063aAb6C9977183D9e72835428") 999808484451757093697730 ``` :::: ### `nonces` ::::description[`StableSwap.nonces(arg0: address) -> uint256: view`] Getter for the nonce. Returns: nonces (`uint256`). | Input | Type | Description | | ----------- | -------| ----| | `arg0` | `address` | address | ```vyper nonces: public(HashMap[address, uint256]) ``` :::: ### `salt` ::::description[`StableSwap.salt() -> bytes32: view`] Getter for the salt of the LP token. Returns: salt (`bytes32`). ```vyper salt: public(immutable(bytes32)) @external def __init__( _name: String[32], _symbol: String[10], _A: uint256, _fee: uint256, _offpeg_fee_multiplier: uint256, _ma_exp_time: uint256, _coins: DynArray[address, MAX_COINS], _rate_multipliers: DynArray[uint256, MAX_COINS], _asset_types: DynArray[uint8, MAX_COINS], _method_ids: DynArray[bytes4, MAX_COINS], _oracles: DynArray[address, MAX_COINS], ): ... # EIP712 related params ----------------- NAME_HASH = keccak256(name) salt = block.prevhash CACHED_CHAIN_ID = chain.id CACHED_DOMAIN_SEPARATOR = keccak256( _abi_encode( EIP712_TYPEHASH, NAME_HASH, VERSION_HASH, chain.id, self, salt, ) ) ... ``` ```shell >>> StableSwap.salt() HexBytes('0x814188b56f08130fe7b283343b64baa08f4d207229dc52776968b62b977c8f46') ``` :::: ### `DOMAIN_SEPARATOR` ::::description[`StableSwap.DOMAIN_SEPARATOR() -> bytes32: view`] Getter for the domain separator. Returns: domain separator (`bytes32`). ```vyper CACHED_DOMAIN_SEPARATOR: immutable(bytes32) @view @external def DOMAIN_SEPARATOR() -> bytes32: """ @notice EIP712 domain separator. @return bytes32 Domain Separator set for the current chain. """ return self._domain_separator() @view @internal def _domain_separator() -> bytes32: if chain.id != CACHED_CHAIN_ID: return keccak256( _abi_encode( EIP712_TYPEHASH, NAME_HASH, VERSION_HASH, chain.id, self, salt, ) ) return CACHED_DOMAIN_SEPARATOR ``` ```shell >>> StableSwap.DOMAIN_SEPARATOR() HexBytes('0xf60903716a331f2ad023b28477aceee88e5180cab4694c497f4f9cefac657989') ``` :::: --- ## Admin Controls The following methods are guarded and may only be called by the **`admin`** of the Stableswap-NG Factory. ### `ramp_A` ::::description[`StableSwap.ramp_A(_future_A: uint256, _future_time: uint256):`] :::guard[Guarded Method] This function is only callable by the `admin` of the Factory. ::: Function to ramp amplification coefficient A. Minimum ramp time is 86400 (24h). *Limitations when ramping A:* - `block.timestamp` >= `initial_A_time` + `MIN_RAMP_TIME` - `_future_time` >= `block.timestamp` + `MIN_RAMP_TIME` - `future_A` > 0 - `future_A` < `MAX_A (1000000)` Emits: `RampA` | Input | Type | Description | | ----------- | -------| ----| | `_future_A` | `uint256` | future A value | | `_future_time` | `uint256` | timestamp until ramping should occur; needs to be at least 24h (`MIN_RAMP_TIME`) | ```vyper A_PRECISION: constant(uint256) = 100 MAX_A: constant(uint256) = 10 **6 MAX_A_CHANGE: constant(uint256) = 10 MIN_RAMP_TIME: constant(uint256) = 86400 event RampA: old_A: uint256 new_A: uint256 initial_time: uint256 future_time: uint256 @external def ramp_A(_future_A: uint256, _future_time: uint256): assert msg.sender == factory.admin() # dev: only owner assert block.timestamp >= self.initial_A_time + MIN_RAMP_TIME assert _future_time >= block.timestamp + MIN_RAMP_TIME # dev: insufficient time _initial_A: uint256 = self._A() _future_A_p: uint256 = _future_A * A_PRECISION assert _future_A > 0 and _future_A < MAX_A if _future_A_p < _initial_A: assert _future_A_p * MAX_A_CHANGE >= _initial_A else: assert _future_A_p <= _initial_A * MAX_A_CHANGE self.initial_A = _initial_A self.future_A = _future_A_p self.initial_A_time = block.timestamp self.future_A_time = _future_time log RampA(_initial_A, _future_A_p, block.timestamp, _future_time) ``` :::: ### `stop_ramp_A` ::::description[`StableSwap.stop_ramp_A():`] :::guard[Guarded Method] This function is only callable by the `admin` of the Factory. ::: Function to immediately stop the ramping A. The current value during the ramping process will be finalized as `A`. Emits: `StopRampA` ```vyper event StopRampA: A: uint256 t: uint256 @external def stop_ramp_A(): assert msg.sender == factory.admin() # dev: only owner current_A: uint256 = self._A() self.initial_A = current_A self.future_A = current_A self.initial_A_time = block.timestamp self.future_A_time = block.timestamp # now (block.timestamp < t1) is always False, so we return saved A log StopRampA(current_A, block.timestamp) ``` :::: ### `set_new_fee` ::::description[`StableSwap.set_new_fee(_new_fee: uint256, _new_offpeg_fee_multiplier: uint256):`] :::guard[Guarded Method] This function is only callable by the `admin` of the Factory. ::: Function to set new values for `fee` and `offpeg_fee_multiplier`. *Limitations when setting new parameters:* - `_new_fee` <= `MAX_FEE` (5000000000) - `_new_offpeg_fee_multiplier` * `_new_fee` <= `MAX_FEE` * `FEE_DENOMINATOR` Emits: `ApplyNewFee` | Input | Type | Description | | ----------- | -------| ----| | `_new_fee` | `uint256` | new fee | | `_new_offpeg_fee_multiplier` | `uint256` | new off-peg fee multiplier | ```vyper MAX_FEE: constant(uint256) = 5 * 10 **9 FEE_DENOMINATOR: constant(uint256) = 10 **10 event ApplyNewFee: fee: uint256 offpeg_fee_multiplier: uint256 @external def set_new_fee(_new_fee: uint256, _new_offpeg_fee_multiplier: uint256): assert msg.sender == factory.admin() # set new fee: assert _new_fee <= MAX_FEE self.fee = _new_fee # set new offpeg_fee_multiplier: assert _new_offpeg_fee_multiplier * _new_fee <= MAX_FEE * FEE_DENOMINATOR # dev: offpeg multiplier exceeds maximum self.offpeg_fee_multiplier = _new_offpeg_fee_multiplier log ApplyNewFee(_new_fee, _new_offpeg_fee_multiplier) ``` :::: ### `set_ma_exp_time` ::::description[`StableSwap.set_ma_exp_time(_ma_exp_time: uint256, _D_ma_time: uint256):`] :::guard[Guarded Method] This function is only callable by the `admin` of the Factory. ::: Function to set the moving average window for `ma_exp_time` and `D_ma_time`. *Limitations when setting new fee parameters:* - `_ma_exp_time` and `_D_ma_time` > 0 | Input | Type | Description | | ----------- | -------| ----| | `_ma_exp_time` | `uint256` | new ma exp time | | `_D_ma_time` | `uint256` | new D ma time | ```vyper @external def set_ma_exp_time(_ma_exp_time: uint256, _D_ma_time: uint256): """ @notice Set the moving average window of the price oracles. @param _ma_exp_time Moving average window. It is time_in_seconds / ln(2) """ assert msg.sender == factory.admin() # dev: only owner assert 0 not in [_ma_exp_time, _D_ma_time] self.ma_exp_time = _ma_exp_time self.D_ma_time = _D_ma_time ``` ::::