FA-61674 / Options payoff and settlement / Member archive

FIFO realized P&L for option trades: the excess of a flipping trade is dropped · case 04

Selling more than the long position closes it but never opens the short.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Inputs trades [side B/S, contracts, premium], multiplier and fee per contract. Positions may be long or short. Each trade first closes opposite-direction lots oldest first; realized P&L per matched contract is (close - open) for long lots and (open - close) for short lots, times the multiplier. Any remainder opens a new lot in the trade direction. Fees = contracts traded * fee. Work in cents; return [net position, realized, fees].

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 position flip remainder 1	`[2, -410.0, 4.55]`	`[1, -410.0, 4.55]`	Failed

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