Overview
RektHub uses optimized libraries for bonding curve calculations. These utilities handle the constant product math that powers price discovery and trading.
For Integrators: You typically don’t need to use these libraries
directly—the BondingCurve contract handles all calculations. This reference is
useful if you’re building off-chain quoters, simulators, or custom trading
algorithms.
BondingCurveMath
The core library for constant product (x × y = k) bonding curve calculations.
Location: contracts/libraries/BondingCurveMath.sol
Purpose
- Calculate token outputs for buy orders
- Calculate native outputs for sell orders
- Calculate fees as percentages (basis points)
- Pure functions—no state modifications
Functions
calculateBuyReturn
Calculate how many tokens a buyer will receive for a given native token input.
function calculateBuyReturn(
uint256 nativeAmount,
uint256 virtualNativeReserves,
uint256 virtualTokenReserves
) internal pure returns (uint256 tokensOut);
nativeAmount (uint256): Amount of native tokens to spend (after fees)virtualNativeReserves (uint256): Current virtual native reserves in the curvevirtualTokenReserves (uint256): Current virtual token reserves in the curve
Returns:
tokensOut: Amount of tokens the buyer will receive
Formula:
tokensOut = (nativeAmount * virtualTokenReserves) / (virtualNativeReserves + nativeAmount)
x * y = k
Example Usage:
// Off-chain calculation (JavaScript)
function calculateBuyReturn(
nativeAmount,
virtualNativeReserves,
virtualTokenReserves
) {
return (
(nativeAmount * virtualTokenReserves) / (virtualNativeReserves + nativeAmount)
);
}
// Example
const nativeIn = ethers.parseEther('0.1');
const virtualNative = ethers.parseEther('30');
const virtualTokens = ethers.parseEther('1073000000');
const tokensOut = calculateBuyReturn(nativeIn, virtualNative, virtualTokens);
console.log('Will receive:', ethers.formatEther(tokensOut), 'tokens');
Important: This calculates the raw output before considering real reserve
limits. The BondingCurve contract takes the minimum of this calculation and
available real tokens.
calculateSellReturn
Calculate how many native tokens a seller will receive for selling tokens.
function calculateSellReturn(
uint256 tokenAmount,
uint256 virtualNativeReserves,
uint256 virtualTokenReserves
) internal pure returns (uint256 nativeOut);
tokenAmount (uint256): Amount of tokens to sellvirtualNativeReserves (uint256): Current virtual native reserves in the curvevirtualTokenReserves (uint256): Current virtual token reserves in the curve
Returns:
nativeOut: Amount of native tokens the seller will receive (before fees)
Formula:
nativeOut = (tokenAmount * virtualNativeReserves) / (virtualTokenReserves + tokenAmount)
// Off-chain calculation (JavaScript)
function calculateSellReturn(
tokenAmount,
virtualNativeReserves,
virtualTokenReserves
) {
return (
(tokenAmount * virtualNativeReserves) / (virtualTokenReserves + tokenAmount)
);
}
// Example
const tokensToSell = ethers.parseEther('1000000');
const virtualNative = ethers.parseEther('30');
const virtualTokens = ethers.parseEther('1073000000');
const grossNativeOut = calculateSellReturn(
tokensToSell,
virtualNative,
virtualTokens
);
console.log('Gross output:', ethers.formatEther(grossNativeOut));
// Apply 1% fee
const fee = (grossNativeOut * 100n) / 10000n;
const netNativeOut = grossNativeOut - fee;
console.log('Net after fees:', ethers.formatEther(netNativeOut));
Fee Deduction: calculateSellReturn returns the gross amount before fees.
Always subtract the protocol fee (1%) to get the net amount users receive.
calculateFee
Calculate a fee as a percentage using basis points.
function calculateFee(
uint256 amount,
uint256 feeBasisPoints
) internal pure returns (uint256 fee);
amount (uint256): Amount to calculate fee onfeeBasisPoints (uint256): Fee in basis points (100 = 1%, 10000 = 100%)
Returns:
fee: Calculated fee amount
Formula:
fee = (amount * feeBasisPoints) / 10000
// Off-chain calculation
function calculateFee(amount, bps) {
return (amount * bps) / 10000n;
}
// Examples
const amount = ethers.parseEther('100');
const onePercent = calculateFee(amount, 100);
console.log('1% fee:', ethers.formatEther(onePercent));
const thirtyPercent = calculateFee(onePercent, 3000);
console.log('30% of fee:', ethers.formatEther(thirtyPercent));
Basis Points: 1 basis point = 0.01%. Common values: 1% = 100 bps, 5% = 500
bps, 10% = 1000 bps, 100% = 10000 bps
Next Steps
