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crypto-pool

**Crypto-Pools are exchange contracts containing two volatile (non-pegged) assets.**These exchange contracts are deployed via the CryptoSwap Factory. Unlike newer Factory contracts, which utilize blueprint contracts, the earlier versions did not have this feature at the time of their deployments. Instead, in these earlier versions, the exchange contract is created using the Vyper built-in **create_forwarder_to()**function.

The pool is then initialized via the **initialize()**function of the pool implementation contract, which sets all the relevant variables, such as paired tokens, prices, and parameters.

▶Initializing the Pool▼
@external
def initialize(
    A: uint256,
    gamma: uint256,
    mid_fee: uint256,
    out_fee: uint256,
    allowed_extra_profit: uint256,
    fee_gamma: uint256,
    adjustment_step: uint256,
    admin_fee: uint256,
    ma_half_time: uint256,
    initial_price: uint256,
    _token: address,
    _coins: address[N_COINS],
    _precisions: uint256,
):
    assert self.mid_fee == 0  # dev: check that we call it from factory

    self.factory = msg.sender

    # Pack A and gamma:
    # shifted A + gamma
    A_gamma: uint256 = shift(A, 128)
    A_gamma = bitwise_or(A_gamma, gamma)
    self.initial_A_gamma = A_gamma
    self.future_A_gamma = A_gamma

    self.mid_fee = mid_fee
    self.out_fee = out_fee
    self.allowed_extra_profit = allowed_extra_profit
    self.fee_gamma = fee_gamma
    self.adjustment_step = adjustment_step
    self.admin_fee = admin_fee

    self.price_scale = initial_price
    self._price_oracle = initial_price
    self.last_prices = initial_price
    self.last_prices_timestamp = block.timestamp
    self.ma_half_time = ma_half_time

    self.xcp_profit_a = 10**18

    self.token = _token
    self.coins = _coins
    self.PRECISIONS = _precisions

Exchange Methods​

exchange​

CryptoSwap.exchange(i: uint256, j: uint256, dx: uint256, min_dy: uint256, use_eth: bool = False, receiver: address = msg.sender) -> uint256:

Function to exchange dx amount of coin i for coin j and receive a minimum amount of min_dy.

Returns: output amount (uint256).

Emits: TokenExchange

InputTypeDescription
iuint256Index value for the input coin
juint256Index value for the output coin
dxuint256Amount of input coin being swapped in
min_dyuint256Minimum amount of output coin to receive
use_ethboolwhether to use plain ETH; defaults to False (uses wETH instead)
receiveraddressAddress to send output coin to. Deafaults to msg.sender
<>Source code▼
event TokenExchange:
    buyer: indexed(address)
    sold_id: uint256
    tokens_sold: uint256
    bought_id: uint256
    tokens_bought: uint256

@payable
@external
@nonreentrant('lock')
def exchange(i: uint256, j: uint256, dx: uint256, min_dy: uint256,
            use_eth: bool = False, receiver: address = msg.sender) -> uint256:
    """
    Exchange using WETH by default
    """
    return self._exchange(msg.sender, msg.value, i, j, dx, min_dy, use_eth, receiver, ZERO_ADDRESS, EMPTY_BYTES32)

@internal
def _exchange(sender: address, mvalue: uint256, i: uint256, j: uint256, dx: uint256, min_dy: uint256,
            use_eth: bool, receiver: address, callbacker: address, callback_sig: bytes32) -> uint256:
    assert i != j  # dev: coin index out of range
    assert i < N_COINS  # dev: coin index out of range
    assert j < N_COINS  # dev: coin index out of range
    assert dx > 0  # dev: do not exchange 0 coins

    A_gamma: uint256[2] = self._A_gamma()
    xp: uint256[N_COINS] = self.balances
    p: uint256 = 0
    dy: uint256 = 0

    in_coin: address = self.coins[i]
    out_coin: address = self.coins[j]

    y: uint256 = xp[j]
    x0: uint256 = xp[i]
    xp[i] = x0 + dx
    self.balances[i] = xp[i]

    price_scale: uint256 = self.price_scale
    precisions: uint256[2] = self._get_precisions()

    xp = [xp[0] * precisions[0], xp[1] * price_scale * precisions[1] / PRECISION]

    prec_i: uint256 = precisions[0]
    prec_j: uint256 = precisions[1]
    if i == 1:
        prec_i = precisions[1]
        prec_j = precisions[0]

    # In case ramp is happening
    t: uint256 = self.future_A_gamma_time
    if t > 0:
        x0 *= prec_i
        if i > 0:
            x0 = x0 * price_scale / PRECISION
        x1: uint256 = xp[i]  # Back up old value in xp
        xp[i] = x0
        self.D = self.newton_D(A_gamma[0], A_gamma[1], xp)
        xp[i] = x1  # And restore
        if block.timestamp >= t:
            self.future_A_gamma_time = 1

    dy = xp[j] - self.newton_y(A_gamma[0], A_gamma[1], xp, self.D, j)
    # Not defining new "y" here to have less variables / make subsequent calls cheaper
    xp[j] -= dy
    dy -= 1

    if j > 0:
        dy = dy * PRECISION / price_scale
    dy /= prec_j

    dy -= self._fee(xp) * dy / 10**10
    assert dy >= min_dy, "Slippage"
    y -= dy

    self.balances[j] = y

    # Do transfers in and out together
    # XXX coin vs ETH
    if use_eth and in_coin == WETH20:
        assert mvalue == dx  # dev: incorrect eth amount
    else:
        assert mvalue == 0  # dev: nonzero eth amount
        if callback_sig == EMPTY_BYTES32:
            response: Bytes[32] = raw_call(
                in_coin,
                _abi_encode(
                    sender, self, dx, method_id=method_id("transferFrom(address,address,uint256)")
                ),
                max_outsize=32,
            )
            if len(response) != 0:
                assert convert(response, bool)  # dev: failed transfer
        else:
            b: uint256 = ERC20(in_coin).balanceOf(self)
            raw_call(
                callbacker,
                concat(slice(callback_sig, 0, 4), _abi_encode(sender, receiver, in_coin, dx, dy))
            )
            assert ERC20(in_coin).balanceOf(self) - b == dx  # dev: callback didn't give us coins
        if in_coin == WETH20:
            WETH(WETH20).withdraw(dx)

    if use_eth and out_coin == WETH20:
        raw_call(receiver, b"", value=dy)
    else:
        if out_coin == WETH20:
            WETH(WETH20).deposit(value=dy)
        response: Bytes[32] = raw_call(
            out_coin,
            _abi_encode(receiver, dy, method_id=method_id("transfer(address,uint256)")),
            max_outsize=32,
        )
        if len(response) != 0:
            assert convert(response, bool)

    y *= prec_j
    if j > 0:
        y = y * price_scale / PRECISION
    xp[j] = y

    # Calculate price
    if dx > 10**5 and dy > 10**5:
        _dx: uint256 = dx * prec_i
        _dy: uint256 = dy * prec_j
        if i == 0:
            p = _dx * 10**18 / _dy
        else:  # j == 0
            p = _dy * 10**18 / _dx

    self.tweak_price(A_gamma, xp, p, 0)

    log TokenExchange(sender, i, dx, j, dy)

    return dy
▶Example▼
>>> CryptoSwap.exchange()
1696841675

exchange_underlying​

CryptoSwap.exchange_underlying(i: uint256, j: uint256, dx: uint256, min_dy: uint256, receiver: address = msg.sender) -> uint256:
note

exchange_underlying exchanges tokens by using the 'underlying' ETH instead of wETH.

Function to exchange dx amount of coin i for coin j and receive a minimum amount of min_dy.

Returns: output amount (uint256).

Emits: TokenExchange

InputTypeDescription
iuint256index value for the input coin
juint256index value for the output coin
dxuint256amount of input coin being swapped in
min_dyuint256minimum amount of output coin to receive
use_ethboolwhether to use plain ETH; defaults to False (uses wETH instead)
receiveraddressaddress to send output coin to; deafaults to msg.sender
<>Source code▼
event TokenExchange:
    buyer: indexed(address)
    sold_id: uint256
    tokens_sold: uint256
    bought_id: uint256
    tokens_bought: uint256

@payable
@external
@nonreentrant('lock')
def exchange_underlying(i: uint256, j: uint256, dx: uint256, min_dy: uint256,
                        receiver: address = msg.sender) -> uint256:
    """
    Exchange using ETH
    """
    return self._exchange(msg.sender, msg.value, i, j, dx, min_dy, True, receiver, ZERO_ADDRESS, EMPTY_BYTES32)

@internal
def _exchange(sender: address, mvalue: uint256, i: uint256, j: uint256, dx: uint256, min_dy: uint256,
            use_eth: bool, receiver: address, callbacker: address, callback_sig: bytes32) -> uint256:
    assert i != j  # dev: coin index out of range
    assert i < N_COINS  # dev: coin index out of range
    assert j < N_COINS  # dev: coin index out of range
    assert dx > 0  # dev: do not exchange 0 coins

    A_gamma: uint256[2] = self._A_gamma()
    xp: uint256[N_COINS] = self.balances
    p: uint256 = 0
    dy: uint256 = 0

    in_coin: address = self.coins[i]
    out_coin: address = self.coins[j]

    y: uint256 = xp[j]
    x0: uint256 = xp[i]
    xp[i] = x0 + dx
    self.balances[i] = xp[i]

    price_scale: uint256 = self.price_scale
    precisions: uint256[2] = self._get_precisions()

    xp = [xp[0] * precisions[0], xp[1] * price_scale * precisions[1] / PRECISION]

    prec_i: uint256 = precisions[0]
    prec_j: uint256 = precisions[1]
    if i == 1:
        prec_i = precisions[1]
        prec_j = precisions[0]

    # In case ramp is happening
    t: uint256 = self.future_A_gamma_time
    if t > 0:
        x0 *= prec_i
        if i > 0:
            x0 = x0 * price_scale / PRECISION
        x1: uint256 = xp[i]  # Back up old value in xp
        xp[i] = x0
        self.D = self.newton_D(A_gamma[0], A_gamma[1], xp)
        xp[i] = x1  # And restore
        if block.timestamp >= t:
            self.future_A_gamma_time = 1

    dy = xp[j] - self.newton_y(A_gamma[0], A_gamma[1], xp, self.D, j)
    # Not defining new "y" here to have less variables / make subsequent calls cheaper
    xp[j] -= dy
    dy -= 1

    if j > 0:
        dy = dy * PRECISION / price_scale
    dy /= prec_j

    dy -= self._fee(xp) * dy / 10**10
    assert dy >= min_dy, "Slippage"
    y -= dy

    self.balances[j] = y

    # Do transfers in and out together
    # XXX coin vs ETH
    if use_eth and in_coin == WETH20:
        assert mvalue == dx  # dev: incorrect eth amount
    else:
        assert mvalue == 0  # dev: nonzero eth amount
        if callback_sig == EMPTY_BYTES32:
            response: Bytes[32] = raw_call(
                in_coin,
                _abi_encode(
                    sender, self, dx, method_id=method_id("transferFrom(address,address,uint256)")
                ),
                max_outsize=32,
            )
            if len(response) != 0:
                assert convert(response, bool)  # dev: failed transfer
        else:
            b: uint256 = ERC20(in_coin).balanceOf(self)
            raw_call(
                callbacker,
                concat(slice(callback_sig, 0, 4), _abi_encode(sender, receiver, in_coin, dx, dy))
            )
            assert ERC20(in_coin).balanceOf(self) - b == dx  # dev: callback didn't give us coins
        if in_coin == WETH20:
            WETH(WETH20).withdraw(dx)

    if use_eth and out_coin == WETH20:
        raw_call(receiver, b"", value=dy)
    else:
        if out_coin == WETH20:
            WETH(WETH20).deposit(value=dy)
        response: Bytes[32] = raw_call(
            out_coin,
            _abi_encode(receiver, dy, method_id=method_id("transfer(address,uint256)")),
            max_outsize=32,
        )
        if len(response) != 0:
            assert convert(response, bool)

    y *= prec_j
    if j > 0:
        y = y * price_scale / PRECISION
    xp[j] = y

    # Calculate price
    if dx > 10**5 and dy > 10**5:
        _dx: uint256 = dx * prec_i
        _dy: uint256 = dy * prec_j
        if i == 0:
            p = _dx * 10**18 / _dy
        else:  # j == 0
            p = _dy * 10**18 / _dx

    self.tweak_price(A_gamma, xp, p, 0)

    log TokenExchange(sender, i, dx, j, dy)

    return dy
▶Example▼
>>> CryptoSwap.exchange_underlying(todo)

exchange_extended​

CryptoSwap.exchange_extended(i: uint256, j: uint256, dx: uint256, min_dy: uint256, use_eth: bool, sender: address, receiver: address, cb: bytes32) -> uint256:
note

This method does not allow swapping in native token, but does allow swaps that transfer out native token from the pool.

Function to exchange dx amount of coin i for coin j and receive a minimum amount of min_dy with using a callback method.

Returns: output amount (uint256).

Emits: TokenExchange

InputTypeDescription
iuint256index value for the input coin
juint256index value for the output coin
dxuint256amount of input coin being swapped in
min_dyuint256minimum amount of output coin to receive
use_ethboolwhether to use plain ETH; defaults to False (uses wETH instead)
receiveraddressaddress to send output coin to; deafaults to msg.sender
cbbytes32callback signature
<>Source code▼
event TokenExchange:
    buyer: indexed(address)
    sold_id: uint256
    tokens_sold: uint256
    bought_id: uint256
    tokens_bought: uint256

@payable
@external
@nonreentrant('lock')
def exchange_extended(i: uint256, j: uint256, dx: uint256, min_dy: uint256,
                    use_eth: bool, sender: address, receiver: address, cb: bytes32) -> uint256:
    assert cb != EMPTY_BYTES32  # dev: No callback specified
    return self._exchange(sender, msg.value, i, j, dx, min_dy, use_eth, receiver, msg.sender, cb)

@internal
def _exchange(sender: address, mvalue: uint256, i: uint256, j: uint256, dx: uint256, min_dy: uint256,
            use_eth: bool, receiver: address, callbacker: address, callback_sig: bytes32) -> uint256:
    assert i != j  # dev: coin index out of range
    assert i < N_COINS  # dev: coin index out of range
    assert j < N_COINS  # dev: coin index out of range
    assert dx > 0  # dev: do not exchange 0 coins

    A_gamma: uint256[2] = self._A_gamma()
    xp: uint256[N_COINS] = self.balances
    p: uint256 = 0
    dy: uint256 = 0

    in_coin: address = self.coins[i]
    out_coin: address = self.coins[j]

    y: uint256 = xp[j]
    x0: uint256 = xp[i]
    xp[i] = x0 + dx
    self.balances[i] = xp[i]

    price_scale: uint256 = self.price_scale
    precisions: uint256[2] = self._get_precisions()

    xp = [xp[0] * precisions[0], xp[1] * price_scale * precisions[1] / PRECISION]

    prec_i: uint256 = precisions[0]
    prec_j: uint256 = precisions[1]
    if i == 1:
        prec_i = precisions[1]
        prec_j = precisions[0]

    # In case ramp is happening
    t: uint256 = self.future_A_gamma_time
    if t > 0:
        x0 *= prec_i
        if i > 0:
            x0 = x0 * price_scale / PRECISION
        x1: uint256 = xp[i]  # Back up old value in xp
        xp[i] = x0
        self.D = self.newton_D(A_gamma[0], A_gamma[1], xp)
        xp[i] = x1  # And restore
        if block.timestamp >= t:
            self.future_A_gamma_time = 1

    dy = xp[j] - self.newton_y(A_gamma[0], A_gamma[1], xp, self.D, j)
    # Not defining new "y" here to have less variables / make subsequent calls cheaper
    xp[j] -= dy
    dy -= 1

    if j > 0:
        dy = dy * PRECISION / price_scale
    dy /= prec_j

    dy -= self._fee(xp) * dy / 10**10
    assert dy >= min_dy, "Slippage"
    y -= dy

    self.balances[j] = y

    # Do transfers in and out together
    # XXX coin vs ETH
    if use_eth and in_coin == WETH20:
        assert mvalue == dx  # dev: incorrect eth amount
    else:
        assert mvalue == 0  # dev: nonzero eth amount
        if callback_sig == EMPTY_BYTES32:
            response: Bytes[32] = raw_call(
                in_coin,
                _abi_encode(
                    sender, self, dx, method_id=method_id("transferFrom(address,address,uint256)")
                ),
                max_outsize=32,
            )
            if len(response) != 0:
                assert convert(response, bool)  # dev: failed transfer
        else:
            b: uint256 = ERC20(in_coin).balanceOf(self)
            raw_call(
                callbacker,
                concat(slice(callback_sig, 0, 4), _abi_encode(sender, receiver, in_coin, dx, dy))
            )
            assert ERC20(in_coin).balanceOf(self) - b == dx  # dev: callback didn't give us coins
        if in_coin == WETH20:
            WETH(WETH20).withdraw(dx)

    if use_eth and out_coin == WETH20:
        raw_call(receiver, b"", value=dy)
    else:
        if out_coin == WETH20:
            WETH(WETH20).deposit(value=dy)
        response: Bytes[32] = raw_call(
            out_coin,
            _abi_encode(receiver, dy, method_id=method_id("transfer(address,uint256)")),
            max_outsize=32,
        )
        if len(response) != 0:
            assert convert(response, bool)

    y *= prec_j
    if j > 0:
        y = y * price_scale / PRECISION
    xp[j] = y

    # Calculate price
    if dx > 10**5 and dy > 10**5:
        _dx: uint256 = dx * prec_i
        _dy: uint256 = dy * prec_j
        if i == 0:
            p = _dx * 10**18 / _dy
        else:  # j == 0
            p = _dy * 10**18 / _dx

    self.tweak_price(A_gamma, xp, p, 0)

    log TokenExchange(sender, i, dx, j, dy)

    return dy
▶Example▼
>>> CryptoSwap.exchange_extended(todo)

get_dy​

CryptoSwap.get_dy(i: uint256, j: uint256, dx: uint256) -> uint256:

Getter for the received amount of coin j for swapping in dx amount of coin i.

Returns: output amount (uint256).

InputTypeDescription
iuint256index value for the input coin
juint256index value for the output coin
dxuint256amount of input coin being swapped in
note

This method takes fees into consideration.

<>Source code▼
@external
@view
def get_dy(i: uint256, j: uint256, dx: uint256) -> uint256:
    assert i != j  # dev: same input and output coin
    assert i < N_COINS  # dev: coin index out of range
    assert j < N_COINS  # dev: coin index out of range

    precisions: uint256[2] = self._get_precisions()

    price_scale: uint256 = self.price_scale * precisions[1]
    xp: uint256[N_COINS] = self.balances

    A_gamma: uint256[2] = self._A_gamma()
    D: uint256 = self.D
    if self.future_A_gamma_time > 0:
        D = self.newton_D(A_gamma[0], A_gamma[1], self.xp())

    xp[i] += dx
    xp = [xp[0] * precisions[0], xp[1] * price_scale / PRECISION]

    y: uint256 = self.newton_y(A_gamma[0], A_gamma[1], xp, D, j)
    dy: uint256 = xp[j] - y - 1
    xp[j] = y
    if j > 0:
        dy = dy * PRECISION / price_scale
    else:
        dy /= precisions[0]
    dy -= self._fee(xp) * dy / 10**10

    return dy
▶Example▼
>>> CryptoSwap.get_dy(0, 1, 1e18) # get_dy: 1 ETH for dy PRISMA
2244836869048665161301

Adding/Removing Liquidity​

add_liquidity​

CryptoSwap.add_liquidity(amounts: uint256[N_COINS], min_mint_amount: uint256, use_eth: bool = False, receiver: address = msg.sender) -> uint256:

Function to add liquidity to the pool and mint the corresponding lp tokens.

Returns: amount of lp tokens received (uint256).

Emits: AddLiquidity

InputTypeDescription
amountsuint256[N_COINS]list of amounts to add of each coin
min_mint_amountuint256minimum amount of lp tokens to mint
use_ethboolTrue if native token is being added to the pool; default to False
receiveraddressreceiver of the lp tokens; deaults to msg.sender
<>Source code▼
event AddLiquidity:
    provider: indexed(address)
    token_amounts: uint256[N_COINS]
    fee: uint256
    token_supply: uint256

N_COINS: constant(int128) = 2

@payable
@external
@nonreentrant('lock')
def add_liquidity(amounts: uint256[N_COINS], min_mint_amount: uint256,
                use_eth: bool = False, receiver: address = msg.sender) -> uint256:
    assert amounts[0] > 0 or amounts[1] > 0  # dev: no coins to add

    A_gamma: uint256[2] = self._A_gamma()

    xp: uint256[N_COINS] = self.balances
    amountsp: uint256[N_COINS] = empty(uint256[N_COINS])
    xx: uint256[N_COINS] = empty(uint256[N_COINS])
    d_token: uint256 = 0
    d_token_fee: uint256 = 0
    old_D: uint256 = 0

    xp_old: uint256[N_COINS] = xp

    for i in range(N_COINS):
        bal: uint256 = xp[i] + amounts[i]
        xp[i] = bal
        self.balances[i] = bal
    xx = xp

    precisions: uint256[2] = self._get_precisions()

    price_scale: uint256 = self.price_scale * precisions[1]
    xp = [xp[0] * precisions[0], xp[1] * price_scale / PRECISION]
    xp_old = [xp_old[0] * precisions[0], xp_old[1] * price_scale / PRECISION]

    if not use_eth:
        assert msg.value == 0  # dev: nonzero eth amount

    for i in range(N_COINS):
        coin: address = self.coins[i]
        if use_eth and coin == WETH20:
            assert msg.value == amounts[i]  # dev: incorrect eth amount
        if amounts[i] > 0:
            if (not use_eth) or (coin != WETH20):
                response: Bytes[32] = raw_call(
                    coin,
                    _abi_encode(
                        msg.sender,
                        self,
                        amounts[i],
                        method_id=method_id("transferFrom(address,address,uint256)"),
                    ),
                    max_outsize=32,
                )
                if len(response) != 0:
                    assert convert(response, bool)  # dev: failed transfer
                if coin == WETH20:
                    WETH(WETH20).withdraw(amounts[i])
            amountsp[i] = xp[i] - xp_old[i]

    t: uint256 = self.future_A_gamma_time
    if t > 0:
        old_D = self.newton_D(A_gamma[0], A_gamma[1], xp_old)
        if block.timestamp >= t:
            self.future_A_gamma_time = 1
    else:
        old_D = self.D

    D: uint256 = self.newton_D(A_gamma[0], A_gamma[1], xp)

    lp_token: address = self.token
    token_supply: uint256 = CurveToken(lp_token).totalSupply()
    if old_D > 0:
        d_token = token_supply * D / old_D - token_supply
    else:
        d_token = self.get_xcp(D)  # making initial virtual price equal to 1
    assert d_token > 0  # dev: nothing minted

    if old_D > 0:
        d_token_fee = self._calc_token_fee(amountsp, xp) * d_token / 10**10 + 1
        d_token -= d_token_fee
        token_supply += d_token
        CurveToken(lp_token).mint(receiver, d_token)

        # Calculate price
        # p_i * (dx_i - dtoken / token_supply * xx_i) = sum{k!=i}(p_k * (dtoken / token_supply * xx_k - dx_k))
        # Simplified for 2 coins
        p: uint256 = 0
        if d_token > 10**5:
            if amounts[0] == 0 or amounts[1] == 0:
                S: uint256 = 0
                precision: uint256 = 0
                ix: uint256 = 0
                if amounts[0] == 0:
                    S = xx[0] * precisions[0]
                    precision = precisions[1]
                    ix = 1
                else:
                    S = xx[1] * precisions[1]
                    precision = precisions[0]
                S = S * d_token / token_supply
                p = S * PRECISION / (amounts[ix] * precision - d_token * xx[ix] * precision / token_supply)
                if ix == 0:
                    p = (10**18)**2 / p

        self.tweak_price(A_gamma, xp, p, D)

    else:
        self.D = D
        self.virtual_price = 10**18
        self.xcp_profit = 10**18
        CurveToken(lp_token).mint(receiver, d_token)

    assert d_token >= min_mint_amount, "Slippage"

    log AddLiquidity(receiver, amounts, d_token_fee, token_supply)

    return d_token
▶Example▼
>>> CryptoSwap.add_liquidity(todo)

calc_token_amount​

CryptoSwap.calc_token_amount(amounts: uint256[N_COINS]) -> uint256:

Function to calculate the amount of tokens to deposit/withdraw to get amounts.

Returns amount of LP tokens (uint256).

InputTypeDescription
_amountuint256[N_COINS]amount of coins to withdraw/deposit
<>Source code▼
@view
@external
def calc_token_amount(amounts: uint256[N_COINS]) -> uint256:
    token_supply: uint256 = CurveToken(self.token).totalSupply()
    precisions: uint256[2] = self._get_precisions()
    price_scale: uint256 = self.price_scale * precisions[1]
    A_gamma: uint256[2] = self._A_gamma()
    xp: uint256[N_COINS] = self.xp()
    amountsp: uint256[N_COINS] = [
        amounts[0] * precisions[0],
        amounts[1] * price_scale / PRECISION]
    D0: uint256 = self.D
    if self.future_A_gamma_time > 0:
        D0 = self.newton_D(A_gamma[0], A_gamma[1], xp)
    xp[0] += amountsp[0]
    xp[1] += amountsp[1]
    D: uint256 = self.newton_D(A_gamma[0], A_gamma[1], xp)
    d_token: uint256 = token_supply * D / D0 - token_supply
    d_token -= self._calc_token_fee(amountsp, xp) * d_token / 10**10 + 1
    return d_token
▶Example▼
>>> CryptoSwap.calc_token_amount(todo)

remove_liquidity​

CryptoSwap.remove_liquidity(_amount: uint256, min_amounts: uint256[N_COINS], use_eth: bool = False, receiver: address = msg.sender):

Function to remove liquidity from the pool and burn the lp tokens. When removing liquidity via this function, no fees are charged as the coins are withdrawin in balanced proportions.

Emits: RemoveLiquidity

InputTypeDescription
_amountuint256[N_COINS]amount of lp tokens to burn
min_amountsuint256[N_COINS]minimum amounts of token to withdraw
use_ethboolTrue = withdraw ETH, False = withdraw wETH
receiveraddressreceiver of the coins; defaults to msg.sender
<>Source code▼
event RemoveLiquidity:
    provider: indexed(address)
    token_amounts: uint256[N_COINS]
    token_supply: uint256

N_COINS: constant(int128) = 2

@external
@nonreentrant('lock')
def remove_liquidity(_amount: uint256, min_amounts: uint256[N_COINS],
                    use_eth: bool = False, receiver: address = msg.sender):
    """
    This withdrawal method is very safe, does no complex math
    """
    lp_token: address = self.token
    total_supply: uint256 = CurveToken(lp_token).totalSupply()
    CurveToken(lp_token).burnFrom(msg.sender, _amount)
    balances: uint256[N_COINS] = self.balances
    amount: uint256 = _amount - 1  # Make rounding errors favoring other LPs a tiny bit

    for i in range(N_COINS):
        d_balance: uint256 = balances[i] * amount / total_supply
        assert d_balance >= min_amounts[i]
        self.balances[i] = balances[i] - d_balance
        balances[i] = d_balance  # now it's the amounts going out
        coin: address = self.coins[i]
        if use_eth and coin == WETH20:
            raw_call(receiver, b"", value=d_balance)
        else:
            if coin == WETH20:
                WETH(WETH20).deposit(value=d_balance)
            response: Bytes[32] = raw_call(
                coin,
                _abi_encode(receiver, d_balance, method_id=method_id("transfer(address,uint256)")),
                max_outsize=32,
            )
            if len(response) != 0:
                assert convert(response, bool)

    D: uint256 = self.D
    self.D = D - D * amount / total_supply

    log RemoveLiquidity(msg.sender, balances, total_supply - _amount)
▶Example▼
>>> CryptoSwap.remove_liquidity(todo)

remove_liquidity_one_coin​

CryptoSwap.remove_liquidity_one_coin(token_amount: uint256, i: uint256, min_amount: uint256, use_eth: bool = False, receiver: address = msg.sender) -> uint256:

Funtion to withdraw liquidity in a single token.

Returns: amount of withdrawn coin (uint256).

Emits: RemoveLiquidityOne

InputTypeDescription
token_amountuint256amount of lp tokens to burn
iuint256index of the token to withdraw
min_amountuint256minimum amount of token to withdraw
use_ethboolTrue = withdraw ETH, False = withdraw wETH
receiveraddressreceiver of the coins; defaults to msg.sender
<>Source code▼
event RemoveLiquidityOne:
    provider: indexed(address)
    token_amount: uint256
    coin_index: uint256
    coin_amount: uint256

@external
@nonreentrant('lock')
def remove_liquidity_one_coin(token_amount: uint256, i: uint256, min_amount: uint256,
                            use_eth: bool = False, receiver: address = msg.sender) -> uint256:
    A_gamma: uint256[2] = self._A_gamma()

    dy: uint256 = 0
    D: uint256 = 0
    p: uint256 = 0
    xp: uint256[N_COINS] = empty(uint256[N_COINS])
    future_A_gamma_time: uint256 = self.future_A_gamma_time
    dy, p, D, xp = self._calc_withdraw_one_coin(A_gamma, token_amount, i, (future_A_gamma_time > 0), True)
    assert dy >= min_amount, "Slippage"

    if block.timestamp >= future_A_gamma_time:
        self.future_A_gamma_time = 1

    self.balances[i] -= dy
    CurveToken(self.token).burnFrom(msg.sender, token_amount)

    coin: address = self.coins[i]
    if use_eth and coin == WETH20:
        raw_call(receiver, b"", value=dy)
    else:
        if coin == WETH20:
            WETH(WETH20).deposit(value=dy)
        response: Bytes[32] = raw_call(
            coin,
            _abi_encode(receiver, dy, method_id=method_id("transfer(address,uint256)")),
            max_outsize=32,
        )
        if len(response) != 0:
            assert convert(response, bool)

    self.tweak_price(A_gamma, xp, p, D)

    log RemoveLiquidityOne(msg.sender, token_amount, i, dy)

    return dy
▶Example▼
>>> CryptoSwap.remove_liquidity_one_coin()

calc_withdraw_one_coin​

CryptoSwap.calc_withdraw_one_coin(token_amount: uint256, i: uint256) -> uint256:

Method to calculate the amount of output token i when burning token_amount of lp tokens, taking fees into condsideration.

Returns: amount of token received (uint256).

InputTypeDescription
token_amountuint256amount of lp tokens burned
iuint256index of the coin to withdraw
note

This method takes fees into consideration.

<>Source code▼
N_COINS: constant(int128) = 2

@view
@external
def calc_withdraw_one_coin(token_amount: uint256, i: uint256) -> uint256:
    return self._calc_withdraw_one_coin(self._A_gamma(), token_amount, i, True, False)[0]

@internal
@view
def _calc_withdraw_one_coin(A_gamma: uint256[2], token_amount: uint256, i: uint256, update_D: bool,
                            calc_price: bool) -> (uint256, uint256, uint256, uint256[N_COINS]):
    token_supply: uint256 = CurveToken(self.token).totalSupply()
    assert token_amount <= token_supply  # dev: token amount more than supply
    assert i < N_COINS  # dev: coin out of range

    xx: uint256[N_COINS] = self.balances
    D0: uint256 = 0
    precisions: uint256[2] = self._get_precisions()

    price_scale_i: uint256 = self.price_scale * precisions[1]
    xp: uint256[N_COINS] = [xx[0] * precisions[0], xx[1] * price_scale_i / PRECISION]
    if i == 0:
        price_scale_i = PRECISION * precisions[0]

    if update_D:
        D0 = self.newton_D(A_gamma[0], A_gamma[1], xp)
    else:
        D0 = self.D

    D: uint256 = D0

    # Charge the fee on D, not on y, e.g. reducing invariant LESS than charging the user
    fee: uint256 = self._fee(xp)
    dD: uint256 = token_amount * D / token_supply
    D -= (dD - (fee * dD / (2 * 10**10) + 1))
    y: uint256 = self.newton_y(A_gamma[0], A_gamma[1], xp, D, i)
    dy: uint256 = (xp[i] - y) * PRECISION / price_scale_i
    xp[i] = y

    # Price calc
    p: uint256 = 0
    if calc_price and dy > 10**5 and token_amount > 10**5:
        # p_i = dD / D0 * sum'(p_k * x_k) / (dy - dD / D0 * y0)
        S: uint256 = 0
        precision: uint256 = precisions[0]
        if i == 1:
            S = xx[0] * precisions[0]
            precision = precisions[1]
        else:
            S = xx[1] * precisions[1]
        S = S * dD / D0
        p = S * PRECISION / (dy * precision - dD * xx[i] * precision / D0)
        if i == 0:
            p = (10**18)**2 / p

    return dy, p, D, xp
▶Example▼
>>> CryptoSwap.calc_withdraw_one_coin(1000000000000000000, 0) # withdraw 1 LP token in coin[0]
43347133051647883

Oracles Methods​

Oracle prices are updated whenever the tweak_price function is called. This occurs when any of the _exchange(), add_liquidity(), or remove_liquidity_one_coin() functions are called.

<>Source code▼

@internal
def tweak_price(A_gamma: uint256[2],_xp: uint256[N_COINS], p_i: uint256, new_D: uint256):
    price_oracle: uint256 = self._price_oracle
    last_prices: uint256 = self.last_prices
    price_scale: uint256 = self.price_scale
    last_prices_timestamp: uint256 = self.last_prices_timestamp
    p_new: uint256 = 0

    if last_prices_timestamp < block.timestamp:
        # MA update required
        ma_half_time: uint256 = self.ma_half_time
        alpha: uint256 = self.halfpow((block.timestamp - last_prices_timestamp) * 10**18 / ma_half_time)
        price_oracle = (last_prices * (10**18 - alpha) + price_oracle * alpha) / 10**18
        self._price_oracle = price_oracle
        self.last_prices_timestamp = block.timestamp

    D_unadjusted: uint256 = new_D  # Withdrawal methods know new D already
    if new_D == 0:
        # We will need this a few times (35k gas)
        D_unadjusted = self.newton_D(A_gamma[0], A_gamma[1], _xp)

    if p_i > 0:
        last_prices = p_i

    else:
        # calculate real prices
        __xp: uint256[N_COINS] = _xp
        dx_price: uint256 = __xp[0] / 10**6
        __xp[0] += dx_price
        last_prices = price_scale * dx_price / (_xp[1] - self.newton_y(A_gamma[0], A_gamma[1], __xp, D_unadjusted, 1))

    self.last_prices = last_prices

    total_supply: uint256 = CurveToken(self.token).totalSupply()
    old_xcp_profit: uint256 = self.xcp_profit
    old_virtual_price: uint256 = self.virtual_price

    # Update profit numbers without price adjustment first
    xp: uint256[N_COINS] = [D_unadjusted / N_COINS, D_unadjusted * PRECISION / (N_COINS * price_scale)]
    xcp_profit: uint256 = 10**18
    virtual_price: uint256 = 10**18

    if old_virtual_price > 0:
        xcp: uint256 = self.geometric_mean(xp, True)
        virtual_price = 10**18 * xcp / total_supply
        xcp_profit = old_xcp_profit * virtual_price / old_virtual_price

        t: uint256 = self.future_A_gamma_time
        if virtual_price < old_virtual_price and t == 0:
            raise "Loss"
        if t == 1:
            self.future_A_gamma_time = 0

    self.xcp_profit = xcp_profit

    norm: uint256 = price_oracle * 10**18 / price_scale
    if norm > 10**18:
        norm -= 10**18
    else:
        norm = 10**18 - norm
    adjustment_step: uint256 = max(self.adjustment_step, norm / 5)

    needs_adjustment: bool = self.not_adjusted
    # if not needs_adjustment and (virtual_price-10**18 > (xcp_profit-10**18)/2 + self.allowed_extra_profit):
    # (re-arrange for gas efficiency)
    if not needs_adjustment and (virtual_price * 2 - 10**18 > xcp_profit + 2*self.allowed_extra_profit) and (norm > adjustment_step) and (old_virtual_price > 0):
        needs_adjustment = True
        self.not_adjusted = True

    if needs_adjustment:
        if norm > adjustment_step and old_virtual_price > 0:
            p_new = (price_scale * (norm - adjustment_step) + adjustment_step * price_oracle) / norm

            # Calculate balances*prices
            xp = [_xp[0], _xp[1] * p_new / price_scale]

            # Calculate "extended constant product" invariant xCP and virtual price
            D: uint256 = self.newton_D(A_gamma[0], A_gamma[1], xp)
            xp = [D / N_COINS, D * PRECISION / (N_COINS * p_new)]
            # We reuse old_virtual_price here but it's not old anymore
            old_virtual_price = 10**18 * self.geometric_mean(xp, True) / total_supply

            # Proceed if we've got enough profit
            # if (old_virtual_price > 10**18) and (2 * (old_virtual_price - 10**18) > xcp_profit - 10**18):
            if (old_virtual_price > 10**18) and (2 * old_virtual_price - 10**18 > xcp_profit):
                self.price_scale = p_new
                self.D = D
                self.virtual_price = old_virtual_price

                return

            else:
                self.not_adjusted = False

                # Can instead do another flag variable if we want to save bytespace
                self.D = D_unadjusted
                self.virtual_price = virtual_price
                self._claim_admin_fees()

                return

    # If we are here, the price_scale adjustment did not happen
    # Still need to update the profit counter and D
    self.D = D_unadjusted
    self.virtual_price = virtual_price

    # norm appeared < adjustment_step after
    if needs_adjustment:
        self.not_adjusted = False
        self._claim_admin_fees()

lp_price​

CryptoSwap.lp_price() -> uint256:

Getter for the approximate LP token price with regard to the token at index 0.

Returns: LP token price (uint256).

<>Source code▼
@external
@view
def lp_price() -> uint256:
    """
    Approximate LP token price
    """
    return 2 * self.virtual_price * self.sqrt_int(self.internal_price_oracle()) / 10**18

@internal
@view
def internal_price_oracle() -> uint256:
    price_oracle: uint256 = self._price_oracle
    last_prices_timestamp: uint256 = self.last_prices_timestamp

    if last_prices_timestamp < block.timestamp:
        ma_half_time: uint256 = self.ma_half_time
        last_prices: uint256 = self.last_prices
        alpha: uint256 = self.halfpow((block.timestamp - last_prices_timestamp) * 10**18 / ma_half_time)
        return (last_prices * (10**18 - alpha) + price_oracle * alpha) / 10**18

    else:
        return price_oracle
▶Example▼
>>> CryptoSwap.lp_price()
41793722011818265

price_oracle​

CryptoSwap.price_oracle() -> uint256:

Getter for the oracle price of the coin at index k with regard to coin at index 0.

Returns: oracle price (uint256).

<>Source code▼
@external
@view
def price_oracle() -> uint256:
    return self.internal_price_oracle()

@internal
@view
def internal_price_oracle() -> uint256:
    price_oracle: uint256 = self._price_oracle
    last_prices_timestamp: uint256 = self.last_prices_timestamp

    if last_prices_timestamp < block.timestamp:
        ma_half_time: uint256 = self.ma_half_time
        last_prices: uint256 = self.last_prices
        alpha: uint256 = self.halfpow((block.timestamp - last_prices_timestamp) * 10**18 / ma_half_time)
        return (last_prices * (10**18 - alpha) + price_oracle * alpha) / 10**18

    else:
        return price_oracle
▶Example▼
>>> CryptoSwap.price_oracle()
409798289826499

last_prices​

CryptoSwap.last_prices() -> uint256: view

Getter for the last price of the coin at index k with regard to the coin at index 0. last_price stores the last price when calling the functions _exchange(), add_liquidity() or remove_liquitiy_one_coin().

Returns: last price (uint256).

<>Source code▼
last_prices: public(uint256)
▶Example▼
>>> CryptoSwap.last_prices()
409119503867160

last_prices_timestamp​

CryptoSwap.last_prices_timestamp() -> uint256: view

Getter for the timestamp of the most recent update for last_prices.

Returns: timestamp (uint256).

<>Source code▼
last_prices_timestamp: public(uint256)
▶Example▼
>>> CryptoSwap.last_prices_timestamp()
1700314907

price_scale​

CryptoSwap.price_scale -> uint256: view

Getter for the price scale of the coin at index k with regard to the coin at index 0. Price scale determines the price band around which liquidity is concentrated and is conditionally updated when calling the functions _exchange(), add_liquidity() or remove_liquitiy_one_coin().

Returns: last price (uint256).

<>Source code▼
price_scale: public(uint256)   # Internal price scale
▶Example▼
>>> CryptoSwap.price_scale()
410228896677145

ma_half_time​

CryptoSwap.ma_half_time() -> uint256: view

Getter for the moving-average (ma) half time in seconds.

Returns: ma half time (uint256).

<>Source code▼
ma_half_time: public(uint256)
▶Example▼
>>> CryptoSwap.ma_half_time()
600

virtual_price​

CryptoSwap.geometric_mean(unsorted_x: uint256[N_COINS], sort: bool) -> uint256:

Getter for the virtual price. This variable is cached, fast to read and mostly used internally.

Returns: virtual price (uint256).

<>Source code▼
virtual_price: public(uint256)  # Cached (fast to read) virtual price also used internally
▶Example▼
>>> CryptoSwap.virtual_price()
1032276363484815360

get_virtual_price​

CryptoSwap.geometric_mean(unsorted_x: uint256[N_COINS], sort: bool) -> uint256:

Getter for the virtual price.

Returns: virtual price (uint256).

<>Source code▼
@external
@view
def get_virtual_price() -> uint256:
    return 10**18 * self.get_xcp(self.D) / CurveToken(self.token).totalSupply()
▶Example▼
>>> CryptoSwap.get_virtual_price()
1032276363484815360

Fee Methods​

Fees are charged based on the balance/imbalance of the pool. Fee is low when the pool is balanced and increases the more it is imbalanced.

fee​

CryptoSwap.fee() -> uint256:

Getter for the fee charged by the pool at the current state.

Returns: fee (uint256).

<>Source code▼
@external
@view
def fee() -> uint256:
    return self._fee(self.xp())

@internal
@view
def _fee(xp: uint256[N_COINS]) -> uint256:
    """
    f = fee_gamma / (fee_gamma + (1 - K))
    where
    K = prod(x) / (sum(x) / N)**N
    (all normalized to 1e18)
    """
    fee_gamma: uint256 = self.fee_gamma
    f: uint256 = xp[0] + xp[1]  # sum
    f = fee_gamma * 10**18 / (
        fee_gamma + 10**18 - (10**18 * N_COINS**N_COINS) * xp[0] / f * xp[1] / f
    )
    return (self.mid_fee * f + self.out_fee * (10**18 - f)) / 10**18
▶Example▼
>>> CryptoSwap.fee()
26417626

mid_fee​

CryptoSwap.mid_fee() -> uint256: view

Getter for the current 'mid-fee'. This is the minimum fee and is charged when the pool is completely balanced.

Returns: mid fee (uint256).

<>Source code▼
mid_fee: public(uint256)
▶Example▼
>>> CryptoSwap.mid_fee()
26000000

out_fee​

CryptoSwap.out_fee() -> uint256: view

Getter for the 'out-fee'. This is the maximum fee and is charged when the pool is completely imbalanced.

Returns: out fee (uint256).

<>Source code▼
out_fee: public(uint256)
▶Example▼
>>> CryptoSwap.out_fee()
45000000

fee_gamma​

CryptoSwap.fee_gamma() -> uint256: view

Getter for the 'fee-gamma'. This parameter modifies the rate at which fees rise as imbalance intensifies. Smaller values result in rapid fee hikes with growing imbalances, while larger values lead to more gradual increments in fees as imbalance expands.

Returns: fee gamma (uint256).

<>Source code▼
fee_gamma: public(uint256)
▶Example▼
>>> CryptoSwap.fee_gamma()
230000000000000

xcp_profit​

CryptoSwap.xcp_profit() -> uint256: view

Getter for the current pool profits.

Returns: current profits (uint256).

<>Source code▼
xcp_profit: public(uint256)
▶Example▼
>>> CryptoSwap.xcp_profit()
1058938494058326335

xcp_profit_a​

CryptoSwap.xcp_profit_a() -> uint256:

Getter for the full profit at the last claim of admin fees.

Returns: profit at last claim (uint256).

<>Source code▼
xcp_profit_a: public(uint256)  # Full profit at last claim of admin fees
▶Example▼
>>> CryptoSwap.xcp_profit_a()
1058927586013478083

admin_fee​

CryptoSwap.admin_fee() -> uint256:

Getter for the admin fee of the pool. This value is hardcoded to 50% (5000000000).

Returns: admin fee (uint256).

<>Source code▼
admin_fee: public(uint256)
▶Example▼
>>> CryptoSwap.admin_fee()
5000000000

claim_admin_fees​

CryptoSwap.admin_fee() -> uint256:

Function to claim admin fees from the pool and send them to the fee receiver. fee_receiver is set within the Factory.

Emits: ClaimAdminFee

<>Source code▼
event ClaimAdminFee:
    admin: indexed(address)
    tokens: uint256

@external
@nonreentrant('lock')
def claim_admin_fees():
    self._claim_admin_fees()

@internal
def _claim_admin_fees():
    A_gamma: uint256[2] = self._A_gamma()

    xcp_profit: uint256 = self.xcp_profit
    xcp_profit_a: uint256 = self.xcp_profit_a

    # Gulp here
    for i in range(N_COINS):
        coin: address = self.coins[i]
        if coin == WETH20:
            self.balances[i] = self.balance
        else:
            self.balances[i] = ERC20(coin).balanceOf(self)

    vprice: uint256 = self.virtual_price

    if xcp_profit > xcp_profit_a:
        fees: uint256 = (xcp_profit - xcp_profit_a) * self.admin_fee / (2 * 10**10)
        if fees > 0:
            receiver: address = Factory(self.factory).fee_receiver()
            if receiver != ZERO_ADDRESS:
                frac: uint256 = vprice * 10**18 / (vprice - fees) - 10**18
                claimed: uint256 = CurveToken(self.token).mint_relative(receiver, frac)
                xcp_profit -= fees*2
                self.xcp_profit = xcp_profit
                log ClaimAdminFee(receiver, claimed)

    total_supply: uint256 = CurveToken(self.token).totalSupply()

    # Recalculate D b/c we gulped
    D: uint256 = self.newton_D(A_gamma[0], A_gamma[1], self.xp())
    self.D = D

    self.virtual_price = 10**18 * self.get_xcp(D) / total_supply

    if xcp_profit > xcp_profit_a:
        self.xcp_profit_a = xcp_profit
▶Example▼
>>> CryptoSwap.claim_admin_fees()

Price Scaling​

Curve v2 pools adaptively adjust liquidity to optimize depth near prevailing market prices, thereby reducing slippage. This is achieved by maintaining a continuous EMA (exponential moving average) of the pool's recent exchange rates (termed "internal oracle"), and relocating liquidity around this EMA when it's economically sensible for LPs.

You can envision this mechanism as "resetting" the bonding curve to align the peak liquidity concentration (the curve's center) with the EMA. The price with the highest liquidity focus is termed the "price scale", while the ongoing EMA is labeled as the "price oracle."

The price scaling parameters can be adjusted by the admin of the pool, see here.

allowed_extra_profit​

CryptoSwap.allowed_extra_profit() -> uint256: view

Getter for the allowed extra profit.

Returns: extra profit allowed (uint256).

<>Source code▼
allowed_extra_profit: public(uint256)  # 2 * 10**12 - recommended value
▶Example▼
>>> CryptoSwap.allowed_extra_profit()
2000000000000

adjustment_step​

CryptoSwap.adjustment_step() -> uint256: view

Getter for the minimum size of price scale adjustments.

Returns: adjustment step (uint256).

<>Source code▼
adjustment_step: public(uint256)
▶Example▼
>>> CryptoSwap.adjustment_step()
146000000000000

Bonding Curve Parameters​

Similar to many AMMs, Curve v2 employs a bonding curve to determine asset prices based on the pool's availability of each asset. To centralize liquidity near the bonding curve's midpoint, Curve v2 utilizes an invariant that sits between the Stableswap (Curve v1) and the constant-product models (like Uniswap, Balancer, and others).

The bonding curve parameters can be adjusted by the admin of the pool, see here.

A​

CryptoSwap.A() -> uint256:

Getter for the current pool amplification value.

Returns: A (uint256).

<>Source code▼
@view
@external
def A() -> uint256:
    return self._A_gamma()[0]

@view
@internal
def _A_gamma() -> uint256[2]:
    t1: uint256 = self.future_A_gamma_time

    A_gamma_1: uint256 = self.future_A_gamma
    gamma1: uint256 = bitwise_and(A_gamma_1, 2**128-1)
    A1: uint256 = shift(A_gamma_1, -128)

    if block.timestamp < t1:
        # handle ramping up and down of A
        A_gamma_0: uint256 = self.initial_A_gamma
        t0: uint256 = self.initial_A_gamma_time

        # Less readable but more compact way of writing and converting to uint256
        # gamma0: uint256 = bitwise_and(A_gamma_0, 2**128-1)
        # A0: uint256 = shift(A_gamma_0, -128)
        # A1 = A0 + (A1 - A0) * (block.timestamp - t0) / (t1 - t0)
        # gamma1 = gamma0 + (gamma1 - gamma0) * (block.timestamp - t0) / (t1 - t0)

        t1 -= t0
        t0 = block.timestamp - t0
        t2: uint256 = t1 - t0

        A1 = (shift(A_gamma_0, -128) * t2 + A1 * t0) / t1
        gamma1 = (bitwise_and(A_gamma_0, 2**128-1) * t2 + gamma1 * t0) / t1

    return [A1, gamma1]
▶Example▼
>>> CryptoSwap.A()
400000

gamma​

CryptoSwap.gamma() -> uint256:

Getter for the current gamma value.

Returns: gamma (uint256).

<>Source code▼
@view
@external
def gamma() -> uint256:
    return self._A_gamma()[1]

@view
@internal
def _A_gamma() -> uint256[2]:
    t1: uint256 = self.future_A_gamma_time

    A_gamma_1: uint256 = self.future_A_gamma
    gamma1: uint256 = bitwise_and(A_gamma_1, 2**128-1)
    A1: uint256 = shift(A_gamma_1, -128)

    if block.timestamp < t1:
        # handle ramping up and down of A
        A_gamma_0: uint256 = self.initial_A_gamma
        t0: uint256 = self.initial_A_gamma_time

        # Less readable but more compact way of writing and converting to uint256
        # gamma0: uint256 = bitwise_and(A_gamma_0, 2**128-1)
        # A0: uint256 = shift(A_gamma_0, -128)
        # A1 = A0 + (A1 - A0) * (block.timestamp - t0) / (t1 - t0)
        # gamma1 = gamma0 + (gamma1 - gamma0) * (block.timestamp - t0) / (t1 - t0)

        t1 -= t0
        t0 = block.timestamp - t0
        t2: uint256 = t1 - t0

        A1 = (shift(A_gamma_0, -128) * t2 + A1 * t0) / t1
        gamma1 = (bitwise_and(A_gamma_0, 2**128-1) * t2 + gamma1 * t0) / t1

    return [A1, gamma1]
▶Example▼
>>> CryptoSwap.gamma()
145000000000000

Contract Info Methods​

coins​

CryptoSwap.coins(arg0: uint256) -> address: view

Getter for the coin at index arg0.

Returns: coin (address).

InputTypeDescription
arg0uint256index of coin
<>Source code▼
coins: public(address[N_COINS])
▶Example▼
>>> CryptoSwap.coins(0)
'0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2'

balances​

CryptoSwap.balances(arg0: uint256) -> uint256: view

Getter for the pool balance of coin at index arg0.

Returns: coin balance (uint256).

InputTypeDescription
arg0uint256index of coin
<>Source code▼
coins: public(address[N_COINS])
▶Example▼
>>> CryptoSwap.balances(0)
669157518183204053847

D​

CryptoSwap.D() -> uint256: view

Getter for the D invariant.

Returns: D (address).

<>Source code▼
D: public(uint256)
▶Example▼
>>> CryptoSwap.D()
1386359478656960977136

token​

CryptoSwap.token() -> uint256: view

Getter for the LP token contract.

Returns: lp token (address).

<>Source code▼
token: public(address)
▶Example▼
>>> CryptoSwap.token()
'0xb34e1a3D07f9D180Bc2FDb9Fd90B8994423e33c1'

factory​

CryptoSwap.factory()

Getter for the factory contract.

Returns: factory (address).

<>Source code▼
factory: public(address)
▶Example▼
>>> CryptoSwap.factory()
'0xF18056Bbd320E96A48e3Fbf8bC061322531aac99'

Internal Math Functions​

All these math functions are interally embedded into the contract. They can not be called externally.

geometric_mean​

CryptoSwap.geometric_mean(unsorted_x: uint256[N_COINS], sort: bool) -> uint256:

Function to calculate the geometric mean of a list of numbers in 1e18 precision.

Returns: gemoetric mean (uint256).

InputTypeDescription
unsorted_xuint256[N_COINS]array containing two values
sortboolwhether to sort or not
<>Source code▼
N_COINS: constant(int128) = 2

@internal
@pure
def geometric_mean(unsorted_x: uint256[N_COINS], sort: bool) -> uint256:
    """
    (x[0] * x[1] * ...) **(1/N)
    """
    x: uint256[N_COINS] = unsorted_x
    if sort and x[0] < x[1]:
        x = [unsorted_x[1], unsorted_x[0]]
    D: uint256 = x[0]
    diff: uint256 = 0
    for i in range(255):
        D_prev: uint256 = D
        # tmp: uint256 = 10**18
        # for _x in x:
        #     tmp = tmp * _x / D
        # D = D * ((N_COINS - 1) * 10**18 + tmp) / (N_COINS * 10**18)
        # line below makes it for 2 coins
        D = (D + x[0] * x[1] / D) / N_COINS
        if D > D_prev:
            diff = D - D_prev
        else:
            diff = D_prev - D
        if diff <= 1 or diff * 10**18 < D:
            return D
    raise "Did not converge"

newton_D​

CryptoSwap.newton_D(ANN: uint256, gamma: uint256, x_unsorted: uint256[N_COINS]) -> uint256:

Function to find the D invariant using Newton method.

Returns: D invariant (uint256).

InputTypeDescription
AMNuint256ANN = A * N**N
gammauint256AMM.gamma() value
x_unsorteduint256[N_COINS]unsorted array of coin balances
<>Source code▼
N_COINS: constant(int128) = 2

@internal
@view
def newton_D(ANN: uint256, gamma: uint256, x_unsorted: uint256[N_COINS]) -> uint256:
    """
    Finding the invariant using Newton method.
    ANN is higher by the factor A_MULTIPLIER
    ANN is already A * N**N

    Currently uses 60k gas
    """
    # Safety checks
    assert ANN > MIN_A - 1 and ANN < MAX_A + 1  # dev: unsafe values A
    assert gamma > MIN_GAMMA - 1 and gamma < MAX_GAMMA + 1  # dev: unsafe values gamma

    # Initial value of invariant D is that for constant-product invariant
    x: uint256[N_COINS] = x_unsorted
    if x[0] < x[1]:
        x = [x_unsorted[1], x_unsorted[0]]

    assert x[0] > 10**9 - 1 and x[0] < 10**15 * 10**18 + 1  # dev: unsafe values x[0]
    assert x[1] * 10**18 / x[0] > 10**14-1  # dev: unsafe values x[i] (input)

    D: uint256 = N_COINS * self.geometric_mean(x, False)
    S: uint256 = x[0] + x[1]

    for i in range(255):
        D_prev: uint256 = D

        # K0: uint256 = 10**18
        # for _x in x:
        #     K0 = K0 * _x * N_COINS / D
        # collapsed for 2 coins
        K0: uint256 = (10**18 * N_COINS**2) * x[0] / D * x[1] / D

        _g1k0: uint256 = gamma + 10**18
        if _g1k0 > K0:
            _g1k0 = _g1k0 - K0 + 1
        else:
            _g1k0 = K0 - _g1k0 + 1

        # D / (A * N**N) * _g1k0**2 / gamma**2
        mul1: uint256 = 10**18 * D / gamma * _g1k0 / gamma * _g1k0 * A_MULTIPLIER / ANN

        # 2*N*K0 / _g1k0
        mul2: uint256 = (2 * 10**18) * N_COINS * K0 / _g1k0

        neg_fprime: uint256 = (S + S * mul2 / 10**18) + mul1 * N_COINS / K0 - mul2 * D / 10**18

        # D -= f / fprime
        D_plus: uint256 = D * (neg_fprime + S) / neg_fprime
        D_minus: uint256 = D*D / neg_fprime
        if 10**18 > K0:
            D_minus += D * (mul1 / neg_fprime) / 10**18 * (10**18 - K0) / K0
        else:
            D_minus -= D * (mul1 / neg_fprime) / 10**18 * (K0 - 10**18) / K0

        if D_plus > D_minus:
            D = D_plus - D_minus
        else:
            D = (D_minus - D_plus) / 2

        diff: uint256 = 0
        if D > D_prev:
            diff = D - D_prev
        else:
            diff = D_prev - D
        if diff * 10**14 < max(10**16, D):  # Could reduce precision for gas efficiency here
            # Test that we are safe with the next newton_y
            for _x in x:
                frac: uint256 = _x * 10**18 / D
                assert (frac > 10**16 - 1) and (frac < 10**20 + 1)  # dev: unsafe values x[i]
            return D

    raise "Did not converge"

newton_y​

CryptoSwap.newton_y(ANN: uint256, gamma: uint256, x: uint256[N_COINS], D: uint256, i: uint256) -> uint256:

Function to calculate x[i] given balances x and invariant D.

Returns: y (uint256).

InputTypeDescription
AMNuint256ANN = A * N**N
gammauint256AMM.gamma() value
xuint256[N_COINS]array containing coin balances
Duint256D invariant
iuint256coin index to calculate x[i] for
<>Source code▼
N_COINS: constant(int128) = 2

@internal
@pure
def newton_y(ANN: uint256, gamma: uint256, x: uint256[N_COINS], D: uint256, i: uint256) -> uint256:
    """
    Calculating x[i] given other balances x[0..N_COINS-1] and invariant D
    ANN = A * N**N
    """
    # Safety checks
    assert ANN > MIN_A - 1 and ANN < MAX_A + 1  # dev: unsafe values A
    assert gamma > MIN_GAMMA - 1 and gamma < MAX_GAMMA + 1  # dev: unsafe values gamma
    assert D > 10**17 - 1 and D < 10**15 * 10**18 + 1 # dev: unsafe values D

    x_j: uint256 = x[1 - i]
    y: uint256 = D**2 / (x_j * N_COINS**2)
    K0_i: uint256 = (10**18 * N_COINS) * x_j / D
    # S_i = x_j

    # frac = x_j * 1e18 / D => frac = K0_i / N_COINS
    assert (K0_i > 10**16*N_COINS - 1) and (K0_i < 10**20*N_COINS + 1)  # dev: unsafe values x[i]

    # x_sorted: uint256[N_COINS] = x
    # x_sorted[i] = 0
    # x_sorted = self.sort(x_sorted)  # From high to low
    # x[not i] instead of x_sorted since x_soted has only 1 element

    convergence_limit: uint256 = max(max(x_j / 10**14, D / 10**14), 100)

    for j in range(255):
        y_prev: uint256 = y

        K0: uint256 = K0_i * y * N_COINS / D
        S: uint256 = x_j + y

        _g1k0: uint256 = gamma + 10**18
        if _g1k0 > K0:
            _g1k0 = _g1k0 - K0 + 1
        else:
            _g1k0 = K0 - _g1k0 + 1

        # D / (A * N**N) * _g1k0**2 / gamma**2
        mul1: uint256 = 10**18 * D / gamma * _g1k0 / gamma * _g1k0 * A_MULTIPLIER / ANN

        # 2*K0 / _g1k0
        mul2: uint256 = 10**18 + (2 * 10**18) * K0 / _g1k0

        yfprime: uint256 = 10**18 * y + S * mul2 + mul1
        _dyfprime: uint256 = D * mul2
        if yfprime < _dyfprime:
            y = y_prev / 2
            continue
        else:
            yfprime -= _dyfprime
        fprime: uint256 = yfprime / y

        # y -= f / f_prime;  y = (y * fprime - f) / fprime
        # y = (yfprime + 10**18 * D - 10**18 * S) // fprime + mul1 // fprime * (10**18 - K0) // K0
        y_minus: uint256 = mul1 / fprime
        y_plus: uint256 = (yfprime + 10**18 * D) / fprime + y_minus * 10**18 / K0
        y_minus += 10**18 * S / fprime

        if y_plus < y_minus:
            y = y_prev / 2
        else:
            y = y_plus - y_minus

        diff: uint256 = 0
        if y > y_prev:
            diff = y - y_prev
        else:
            diff = y_prev - y
        if diff < max(convergence_limit, y / 10**14):
            frac: uint256 = y * 10**18 / D
            assert (frac > 10**16 - 1) and (frac < 10**20 + 1)  # dev: unsafe value for y
            return y

    raise "Did not converge"

halfpow​

CryptoSwap.halfpow(power: uint256) -> uint256:

Function to calculate the halfpow.

Returns: halfpow (uint256).

InputTypeDescription
poweruint256value
<>Source code▼
@internal
@pure
def halfpow(power: uint256) -> uint256:
    """
    1e18 * 0.5 **(power/1e18)

    Inspired by: https://github.com/balancer-labs/balancer-core/blob/master/contracts/BNum.sol#L128
    """
    intpow: uint256 = power / 10**18
    otherpow: uint256 = power - intpow * 10**18
    if intpow > 59:
        return 0
    result: uint256 = 10**18 / (2**intpow)
    if otherpow == 0:
        return result

    term: uint256 = 10**18
    x: uint256 = 5 * 10**17
    S: uint256 = 10**18
    neg: bool = False

    for i in range(1, 256):
        K: uint256 = i * 10**18
        c: uint256 = K - 10**18
        if otherpow > c:
            c = otherpow - c
            neg = not neg
        else:
            c -= otherpow
        term = term * (c * x / 10**18) / K
        if neg:
            S -= term
        else:
            S += term
        if term < EXP_PRECISION:
            return result * S / 10**18

    raise "Did not converge"