FA-84428 / Betting odds conversion / Member archive

Negative overround formatted with floor-division digits · case 03

An under-round book shows "-1.99" style garbage instead of "-0.01".

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Market book analysis for decimal prices (strings, each > 1, else "invalid"). Implied probability is 1/d; book = sum of implied probabilities. Return [overround percent (book - 1) * 100, bookmaker margin percent (1 - 1/book) * 100, fair prices d * book for proportional margin removal], every number rounded half up to two decimals (negative values are rounded toward +infinity at the half) and formatted with two decimals.

Why this case matters

Trading tools report overround and margin separately and derive no-vig fair prices.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: negative format	`["-1.72", "-1.72", ["8.75", "3.60", "3.43", "3.16"]]`	`["-0.28", "-0.28", ["8.75", "3.60", "3.43", "3.16"]]`	Failed

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