FA-72464 / Check-digit algorithms / Member archive

GTIN check digit uses the raw remainder · case 04

Nearly every valid code is rejected.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Validate a GTIN-8, GTIN-12, GTIN-13 or GTIN-14 given as ASCII digits (any other length or character: "malformed"). Weights 3,1 alternate starting with 3 on the digit immediately left of the check digit, so the alignment is from the right for every length. Return [kind, check digit matches].

Why this case matters

Retail and logistics scanners accept several GTIN lengths through one validator.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression ["036000291452"]	`["GTIN-12", false]`	`["GTIN-12", true]`	Failed

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