curve_get_d.vy.txt

#vyper: 0.1.0b16 https://etherscan.io/vyper
# This can (and needs to) be changed at compile time
N_COINS: constant(int128) = 3  # <- change

ZERO256: constant(uint256) = 0  # This hack is really bad XXX
ZEROS: constant(uint256[N_COINS]) = [ZERO256, ZERO256, ZERO256]  # <- change

USE_LENDING: constant(bool[N_COINS]) = [True, True, False]
TETHERED: constant(bool[N_COINS]) = [False, False, True]

FEE_DENOMINATOR: constant(uint256) = 10 ** 10
PRECISION: constant(uint256) = 10 ** 18  # The precision to convert to
PRECISION_MUL: constant(uint256[N_COINS]) = [convert(1, uint256), convert(1000000000000, uint256), convert(1000000000000, uint256)]
# PRECISION_MUL: constant(uint256[N_COINS]) = [
#     PRECISION / convert(PRECISION, uint256),  # DAI
#     PRECISION / convert(10 ** 6, uint256),   # USDC
#     PRECISION / convert(10 ** 6, uint256)]   # USDT
A: constant(uint256) = 2000  # 2 x amplification coefficient

@public
@constant
def get_D(xp: uint256[N_COINS]) -> uint256:
    S: uint256 = 0
    for _x in xp:
        S += _x
    if S == 0:
        return 0

    Dprev: uint256 = 0
    D: uint256 = S
    Ann: uint256 = A * N_COINS
    for _i in range(255):
        D_P: uint256 = D
        for _x in xp:
            D_P = D_P * D / (_x * N_COINS + 1)  # +1 is to prevent /0
        Dprev = D
        D = (Ann * S + D_P * N_COINS) * D / ((Ann - 1) * D + (N_COINS + 1) * D_P)
        # Equality with the precision of 1
        if D > Dprev:
            if D - Dprev <= 1:
                break
        else:
            if Dprev - D <= 1:
                break
    return D
    
@public
@constant
def get_I(xp: uint256[N_COINS]) -> int128:
    S: uint256 = 0
    for _x in xp:
        S += _x
    if S == 0:
        return 0

    Dprev: uint256 = 0
    D: uint256 = S
    Ann: uint256 = A * N_COINS
    for _i in range(255):
        D_P: uint256 = D
        for _x in xp:
            D_P = D_P * D / (_x * N_COINS + 1)  # +1 is to prevent /0
        Dprev = D
        D = (Ann * S + D_P * N_COINS) * D / ((Ann - 1) * D + (N_COINS + 1) * D_P)
        # Equality with the precision of 1
        if D > Dprev:
            if D - Dprev <= 1:
                return _i
        else:
            if Dprev - D <= 1:
                return _i
     
    result: int128 = 1000         
    return result