Is the math in getUniv2DataGivenIn incorrect? about subway HOT 17 CLOSED

Should it be..

let newReserveA = reserveA.add(aIn);

from subway.

You have to subtract the 3% fee right?

let newReserveA = reserveA.add(aInWithFee.div(1000))

from subway.

  public getOutputAmount(inputAmount: CurrencyAmount<Token>): [CurrencyAmount<Token>, Pair] {
    invariant(this.involvesToken(inputAmount.currency), 'TOKEN')
    if (JSBI.equal(this.reserve0.quotient, ZERO) || JSBI.equal(this.reserve1.quotient, ZERO)) {
      throw new InsufficientReservesError()
    }
    const inputReserve = this.reserveOf(inputAmount.currency)
    const outputReserve = this.reserveOf(inputAmount.currency.equals(this.token0) ? this.token1 : this.token0)
    const inputAmountWithFee = JSBI.multiply(inputAmount.quotient, _997)
    const numerator = JSBI.multiply(inputAmountWithFee, outputReserve.quotient)
    const denominator = JSBI.add(JSBI.multiply(inputReserve.quotient, _1000), inputAmountWithFee)
    const outputAmount = CurrencyAmount.fromRawAmount(
      inputAmount.currency.equals(this.token0) ? this.token1 : this.token0,
      JSBI.divide(numerator, denominator)
    )
    if (JSBI.equal(outputAmount.quotient, ZERO)) {
      throw new InsufficientInputAmountError()
    }
    return [outputAmount, new Pair(inputReserve.add(inputAmount), outputReserve.subtract(outputAmount))]
  }

i just looked at how uniswap does it in their sdk and they seem to just add the inputamount to the reserve

from subway.

Yeah but inputAmount wasn't multiplied by 997 @htkcodes . Compared to in this project

from subway.

Yeah but inputAmount wasn't multiplied by 997 @htkcodes . Compared to in this project

const inputAmountWithFee = JSBI.multiply(inputAmount.quotient, _997)

same thing

from subway.

When they return the new reserve amount, they add inputAmount, not inputAmountWithFee.

from subway.

Code is referencing UniswapV2Library.sol

https://github.com/Uniswap/v2-periphery/blob/master/contracts/libraries/UniswapV2Library.sol#L43

Try calculating the amount outs given reserves by hand and compare to the output obtained by the router

from subway.

Yes so input amount in @libevm project is "aIn". Its the same thing @mmarkell

from subway.

Code is referencing UniswapV2Library.sol

https://github.com/Uniswap/v2-periphery/blob/master/contracts/libraries/UniswapV2Library.sol#L43

Try calculating the amount outs given reserves by hand and compare to the output obtained by the router

@libevm the amount out is correct. The reserveA update is not. amountInWithFee is 1000x larger than the actual reserve update, no? Uniswap just doesn't name its variables amountInWithFeeTimes1000 even when they are

from subway.

Right exactly ^^

from subway.

@htkcodes I agree that input amount is the same, but the newly calculated reserves are different.

from subway.

@htkcodes I agree that input amount is the same, but the newly calculated reserves are different.

So i think this should be the fix no?

let newReserveA = reserveA.add(aIn);

Just like the sdk's

from subway.

@libevm the amount out is correct. The reserveA update is not. amountInWithFee is 1000x larger than the actual reserve update, no? Uniswap just doesn't name its variables amountInWithFeeTimes1000 even when they are

@jtsiskin No need for the passive aggressiveness -- I gain nothing open sourcing this

@mmarkell I see, nice find. PRs welcomed!

from subway.

Hmm @libevm when I try to push a PR branch, it says access denied. Do you need to update settings?

from subway.

@mmarkell you'll need to fork it, then make a PR from your fork

from subway.

Oh I see

from subway.

Closed #4

from subway.