FA-61815 / Options payoff and settlement / Member archive

Put-call parity violation detector: the trade labels are swapped · case 05

Rich calls are reported as a buy-call trade.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Inputs call price C, put price P, S, K, r, T, dividend yield q and tolerance. v = (C - P) - (S e^{-qT} - K e^{-rT}). If |v| <= tol return ["none", 0.0]; if v > 0 return ["sell call buy put", v]; else ["buy call sell put", -v], amounts rounded to 6.

Why this case matters

Option expiry, exercise and settlement engines move cash and shares; a wrong branch misstates obligations.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression arbitrage direction 1	`["buy call sell put", 1.1]`	`["sell call buy put", 1.1]`	Failed

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