FA-79537 / Barcode symbology encoding / Member archive

ITF encodes an empty string as start and stop only · case 02

Blank quantity fields produce a symbol that scans as nothing instead of an error.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Encode ASCII digits as Interleaved 2 of 5 element widths (narrow 1, wide = ratio in {2, 2.5, 3}). An odd-length input gets a leading 0. Start is narrow bar/space/bar/space; each digit pair interleaves the first digit's pattern in the bars with the second digit's pattern in the spaces; stop is wide bar, narrow space, narrow bar. Digit patterns use weights 1,2,4,7 plus parity (0 = NNWWN). Invalid input returns None.

Why this case matters

Retail, logistics, pharmacy and document workflows depend on encoders that produce exactly the module pattern, code-set switches, separators and quiet zones scanners expect; one misplaced module or separator makes a label unreadable or, worse, scan as different data.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: empty and single digit input 0	`[1, 1, 1, 1, 3, 1, 1]`	`null`	Failed

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