FA-72432 / Check-digit algorithms / Member archive

ISBN-10 removes only the first hyphen · case 02

Hyphenated ISBNs are reported malformed.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

ISBN-10 validation. Hyphens and spaces are removed; the rest must be nine ASCII digits followed by a digit or uppercase X (value 10), else "malformed". Weights run 10 down to 1 from the left and the number is "valid" when the weighted sum is divisible by 11, else "invalid".

Why this case matters

Catalogue and bookstore systems validate legacy ISBN-10 identifiers on intake.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression ["8-292-84466-X"]	`"malformed"`	`"valid"`	Failed

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