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Invert timestretch when using YieldSpaceMath #45

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Invert timestretch when using YieldSpaceMath #45

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Invert tstretch when using YieldSpaceMath
Padraic-O-Mhuiris Feb 7, 2023
d2a1a90
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Padraic-O-Mhuiris Feb 7, 2023
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12 changes: 9 additions & 3 deletions contracts/libraries/HyperdriveMath.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,10 @@ library HyperdriveMath {
if (_isBondOut && _timeRemaining < 1) {
revert Errors.HyperdriveMath_BaseWithNonzeroTime();
}

// 1/timestretch necessary for YieldSpaceMath
uint256 oneDivT = FixedPointMath.ONE_18.divDown(_timeStretch);

if (_isBondOut) {
// If bonds are being purchased, then the entire trade occurs on the
// curved portion since t = 1.
Expand All @@ -138,7 +142,7 @@ library HyperdriveMath {
_bondReserveAdjustment,
_amountIn,
FixedPointMath.ONE_18,
_timeStretch,
oneDivT,
_sharePrice,
_initialSharePrice,
_isBondOut
Expand All @@ -164,7 +168,7 @@ library HyperdriveMath {
_bondReserveAdjustment,
curveIn,
FixedPointMath.ONE_18,
_timeStretch,
oneDivT,
_sharePrice,
_initialSharePrice,
_isBondOut
Expand Down Expand Up @@ -221,6 +225,8 @@ library HyperdriveMath {
.mulDown(FixedPointMath.ONE_18.sub(_timeRemaining))
.divDown(_sharePrice);
uint256 curveOut = _amountOut.mulDown(_timeRemaining);
// 1/timestretch necessary for YieldSpaceMath
uint256 oneDivT = FixedPointMath.ONE_18.divDown(_timeStretch);
uint256 curveIn = YieldSpaceMath.calculateInGivenOut(
// Credit the share reserves by the flat trade.
_shareReserves.add(flat.divDown(_sharePrice)),
Expand All @@ -229,7 +235,7 @@ library HyperdriveMath {
_bondReserveAdjustment,
curveOut,
FixedPointMath.ONE_18,
_timeStretch,
oneDivT,
_sharePrice,
_initialSharePrice,
false
Expand Down