FA-84555 / Betting odds conversion / Member archive

Liability computed from the unrounded lay stake or the full price · case 05

The liability shown differs from what the exchange will reserve for the placed lay.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Green-up a matched back bet by laying at a later price (both > 1, else "invalid"). The equal-profit lay stake is back_stake * back_price / lay_price rounded half up to a cent. Using that rounded lay stake: liability = lay_stake * (lay_price - 1), profit if the selection wins = back_stake * (back_price - 1) - liability, profit if it loses = lay_stake - back_stake. Money values are exact then rounded half up to cents. Return [lay_stake, liability, profit_win, profit_lose].

Why this case matters

Exchange trading tools compute hedge stakes that equalise profit across outcomes.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
control price shortened	`[1500, 3000, -1000, 500]`	`[1500, 1500, 500, 500]`	Failed

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