Views Contract

The FXSwap Views contract supplies quote and liquidity-calculation methods used by the pool. These methods are useful for offchain search, routing, and simulation, but some are too expensive to call repeatedly from another contract.

Contract Source & Deployment

The deployed FXSwap pool returns its Views address from VIEW(). The verified source is closest to TwocryptoView.vy at commit 387fbe5, compiled with Vyper 0.4.3.

Read VIEW() from the target pool instead of hardcoding a periphery address. The pool's own quote methods forward to its configured Views contract.

All coin and token amounts are raw token units. i and j are pool coin indices and must be 0 or 1.

Exchange Methods

get_dy

Views.get_dy(i: uint256, j: uint256, dx: uint256, swap: address) -> uint256: view

Returns the amount of coins(j) expected for an exact input of dx raw units of coins(i), including the dynamic swap fee.

Input	Description
i	Input coin index
j	Output coin index; must differ from i
dx	Positive input amount in raw coins(i) units
swap	FXSwap pool address

The call reverts for equal or out-of-range indices or a zero input. For ordinary quoting, prefer pool.get_dy(i, j, dx), which routes through the pool's current VIEW() address.

get_dx

Views.get_dx(i: uint256, j: uint256, dy: uint256, swap: address, n_iter: uint256 = 5) -> uint256: view

Estimates the raw coins(i) input required to receive dy raw units of coins(j), including fees. The calculation iteratively adds the estimated output fee and is not an exact-output execution method.

n_iter defaults to 5 and is bounded by the contract at 100. More iterations cost more gas and do not turn the result into an execution guarantee. The call reverts for equal or out-of-range indices or zero dy.

Prefer pool.get_dx(i, j, dy) for the default iteration count. Apply an input buffer, simulate the final transaction, and execute through an exact-input swap with a protected min_dy.

calc_fee_get_dy

Views.calc_fee_get_dy(i: uint256, j: uint256, dx: uint256, swap: address) -> uint256: view

Returns the fee component, denominated in raw coins(j) units, for the exact-input quote described by get_dy. It uses the same index and positive-input guards.

This is an analytical helper. Swap execution emits the realized fee in TokenExchange.

Liquidity Methods

calc_token_amount

Views.calc_token_amount(amounts: uint256[2], deposit: bool, swap: address, donation: bool = False) -> uint256: view

Estimates LP tokens minted for a deposit or burned for a withdrawal, including the applicable liquidity fee.

Input	Description
amounts	Raw amounts ordered as [coins(0), coins(1)]
deposit	true for adding liquidity; false for removing liquidity
swap	FXSwap pool address
donation	Immutable ABI name; set true only when estimating a refuel

For user liquidity, prefer pool.calc_token_amount(amounts, deposit). Call the Views contract directly only when the refuel flag or a separate fee breakdown is required.

calc_withdraw_one_coin

Views.calc_withdraw_one_coin(token_amount: uint256, i: uint256, swap: address) -> uint256: view

Returns the estimated raw amount of coins(i) received for burning token_amount LP units in a one-coin withdrawal, after the approximate fee.

The call requires i < 2 and token_amount <= pool.totalSupply(). Prefer pool.calc_withdraw_one_coin(token_amount, i) for normal integrations.

calc_fee_withdraw_one_coin

Views.calc_fee_withdraw_one_coin(token_amount: uint256, i: uint256, swap: address) -> uint256: view

Returns the approximate fee component for the same one-coin withdrawal. The value is denominated in raw coins(i) units and uses the same guards as calc_withdraw_one_coin.

calc_fee_token_amount

Views.calc_fee_token_amount(amounts: uint256[2], deposit: bool, swap: address, donation: bool = False) -> uint256: view

Returns the liquidity-fee component expressed in LP-token units for a deposit or withdrawal quote. donation=true selects the immutable contract path used to estimate a refuel.

Integration guidance

• Read VIEW() from each allowlisted pool and version the pool and periphery together.
• Prefer the pool-native wrappers for get_dy, get_dx, calc_token_amount, and calc_withdraw_one_coin.
• Use direct Views calls for fee breakdowns or the refuel-specific donation flag.
• Batch offchain calls at one block number so balances, parameters, prices, and supply are consistent.
• Simulate state-changing calldata immediately before submission; a view quote does not reserve pool state.