FAILURE MAP
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FA-79556 / Barcode symbology encoding / Open access

Codabar width adds a gap after the stop character · case 01

The symbol is one narrow module wider than the layout expects.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

One gap per character is added instead of one between adjacent characters.

VERIFIED REPAIR

Add len(text) - 1 gaps.

Unsuccessful approach: Counting gaps only within the body misses the two gaps next to start and stop.

Case contract

Validate and size a Codabar symbol text with a wide:narrow ratio between 2 and 3 inclusive. The first and last characters must be start/stop letters A-D (uppercase only, at least two characters); body characters are 0-9 - $ : / . +. Each character has 7 elements: digits, "-" and "$" have 2 wide elements, ": / . +" and A-D have 3. One narrow gap separates adjacent characters. Return the total width in narrow modules or an error.

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.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(text, ratio):
    if not 2 <= ratio <= 3:
        return {'error': 'ratio'}
    if len(text) < 2:
        return {'error': 'short'}
    if text[0] not in 'ABCD' or text[-1] not in 'ABCD':
        return {'error': 'start-stop'}
    body = text[1:-1]
    for ch in body:
        if ch not in '0123456789-$:/.+':
            return {'error': 'char', 'char': ch}
    total = 0
    for ch in text:
        wides = 2 if ch in '0123456789-$' else 3
        total += (7 - wides) + wides * ratio
    return {'modules': total + len(text)}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('C+B', 3), {'modules': 41}], [('B:0C', 3), {'modules': 53}], [('DA/40D', 2.5), {'error': 'char', 'char': 'A'}], [('AE2$5C', 3), {'error': 'char', 'char': 'E'}], [('a+d', 2.5), {'error': 'start-stop'}], [('ad', 3), {'error': 'start-stop'}], [('C5525D', 1.5), {'error': 'ratio'}], [('B5355D', 3), {'modules': 75}]], [[('CD', 2), {'modules': 21}], [('C//5D', 2.5), {'modules': 60.0}], [('AAA$03d', 4), {'error': 'ratio'}], [('A+3d', 2), {'error': 'start-stop'}], [('a3/AC', 3), {'error': 'start-stop'}], [('A/59$T', 3), {'error': 'start-stop'}], [('C773C', 1.5), {'error': 'ratio'}], [('CA', 3), {'modules': 27}]], [[('B957A', 2.5), {'modules': 57.0}], [('B53C', 2), {'modules': 41}], [('A$7:+d', 1.5), {'error': 'ratio'}], [('a+A', 4), {'error': 'ratio'}], [('a958$3C', 1.5), {'error': 'ratio'}], [('D5357T', 1.5), {'error': 'ratio'}], [('a5C', 2), {'error': 'start-stop'}], [('D5-B', 2.5), {'modules': 46.0}]], [[('A:5B', 2), {'modules': 42}], [('B$D', 2), {'modules': 31}], [('aT', 2.5), {'error': 'start-stop'}], [('D3$20d', 3), {'error': 'start-stop'}], [('C58d', 1.5), {'error': 'ratio'}], [('D/5:3B', 4), {'error': 'ratio'}], [('AA', 1.5), {'error': 'ratio'}], [('A1D', 3), {'modules': 39}]], [[('A-31A', 3), {'modules': 63}], [('A905C', 3), {'modules': 63}], [('aB', 3), {'error': 'start-stop'}], [('Cd', 2), {'error': 'start-stop'}], [('a/D', 3), {'error': 'start-stop'}], [('A117.T', 2.5), {'error': 'start-stop'}], [('aD', 3), {'error': 'start-stop'}], [('C55C', 3), {'modules': 51}]]]
labels = ["regression: intercharacter gaps", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: intercharacter gaps 0{'modules': 42}{'modules': 41}Failed
repair trap 1{'modules': 54}{'modules': 53}Failed
combined fault 2{'char': 'A', 'error': 'char'}{'char': 'A', 'error': 'char'}Passed
control 3{'char': 'E', 'error': 'char'}{'char': 'E', 'error': 'char'}Passed
control 4{'error': 'start-stop'}{'error': 'start-stop'}Passed
boundary 5{'error': 'start-stop'}{'error': 'start-stop'}Passed
boundary 6{'error': 'ratio'}{'error': 'ratio'}Passed
control 7{'modules': 76}{'modules': 75}Failed

SHA-256 / a99cd3d34c4626ecf47021059d2255dcffba6b2abc7d4914aa8a18fd8914ab5a

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(text, ratio):
    if not 2 <= ratio <= 3:
        return {'error': 'ratio'}
    if len(text) < 2:
        return {'error': 'short'}
    if text[0] not in 'ABCD' or text[-1] not in 'ABCD':
        return {'error': 'start-stop'}
    body = text[1:-1]
    for ch in body:
        if ch not in '0123456789-$:/.+':
            return {'error': 'char', 'char': ch}
    total = 0
    for ch in text:
        wides = 2 if ch in '0123456789-$' else 3
        total += (7 - wides) + wides * ratio
    return {'modules': total + len(body) - 1}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('C+B', 3), {'modules': 41}], [('B:0C', 3), {'modules': 53}], [('DA/40D', 2.5), {'error': 'char', 'char': 'A'}], [('AE2$5C', 3), {'error': 'char', 'char': 'E'}], [('a+d', 2.5), {'error': 'start-stop'}], [('ad', 3), {'error': 'start-stop'}], [('C5525D', 1.5), {'error': 'ratio'}], [('B5355D', 3), {'modules': 75}]], [[('CD', 2), {'modules': 21}], [('C//5D', 2.5), {'modules': 60.0}], [('AAA$03d', 4), {'error': 'ratio'}], [('A+3d', 2), {'error': 'start-stop'}], [('a3/AC', 3), {'error': 'start-stop'}], [('A/59$T', 3), {'error': 'start-stop'}], [('C773C', 1.5), {'error': 'ratio'}], [('CA', 3), {'modules': 27}]], [[('B957A', 2.5), {'modules': 57.0}], [('B53C', 2), {'modules': 41}], [('A$7:+d', 1.5), {'error': 'ratio'}], [('a+A', 4), {'error': 'ratio'}], [('a958$3C', 1.5), {'error': 'ratio'}], [('D5357T', 1.5), {'error': 'ratio'}], [('a5C', 2), {'error': 'start-stop'}], [('D5-B', 2.5), {'modules': 46.0}]], [[('A:5B', 2), {'modules': 42}], [('B$D', 2), {'modules': 31}], [('aT', 2.5), {'error': 'start-stop'}], [('D3$20d', 3), {'error': 'start-stop'}], [('C58d', 1.5), {'error': 'ratio'}], [('D/5:3B', 4), {'error': 'ratio'}], [('AA', 1.5), {'error': 'ratio'}], [('A1D', 3), {'modules': 39}]], [[('A-31A', 3), {'modules': 63}], [('A905C', 3), {'modules': 63}], [('aB', 3), {'error': 'start-stop'}], [('Cd', 2), {'error': 'start-stop'}], [('a/D', 3), {'error': 'start-stop'}], [('A117.T', 2.5), {'error': 'start-stop'}], [('aD', 3), {'error': 'start-stop'}], [('C55C', 3), {'modules': 51}]]]
labels = ["regression: intercharacter gaps", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: intercharacter gaps 0{'modules': 39}{'modules': 41}Failed
repair trap 1{'modules': 51}{'modules': 53}Failed
combined fault 2{'char': 'A', 'error': 'char'}{'char': 'A', 'error': 'char'}Passed
control 3{'char': 'E', 'error': 'char'}{'char': 'E', 'error': 'char'}Passed
control 4{'error': 'start-stop'}{'error': 'start-stop'}Passed
boundary 5{'error': 'start-stop'}{'error': 'start-stop'}Passed
boundary 6{'error': 'ratio'}{'error': 'ratio'}Passed
control 7{'modules': 73}{'modules': 75}Failed

SHA-256 / 14c6fe8444c09b310ac692be74b439ef45ee476c41e6ce24251bbd1d1b5e759a

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(text, ratio):
    if not 2 <= ratio <= 3:
        return {'error': 'ratio'}
    if len(text) < 2:
        return {'error': 'short'}
    if text[0] not in 'ABCD' or text[-1] not in 'ABCD':
        return {'error': 'start-stop'}
    body = text[1:-1]
    for ch in body:
        if ch not in '0123456789-$:/.+':
            return {'error': 'char', 'char': ch}
    total = 0
    for ch in text:
        wides = 2 if ch in '0123456789-$' else 3
        total += (7 - wides) + wides * ratio
    return {'modules': total + len(text) - 1}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('C+B', 3), {'modules': 41}], [('B:0C', 3), {'modules': 53}], [('DA/40D', 2.5), {'error': 'char', 'char': 'A'}], [('AE2$5C', 3), {'error': 'char', 'char': 'E'}], [('a+d', 2.5), {'error': 'start-stop'}], [('ad', 3), {'error': 'start-stop'}], [('C5525D', 1.5), {'error': 'ratio'}], [('B5355D', 3), {'modules': 75}]], [[('CD', 2), {'modules': 21}], [('C//5D', 2.5), {'modules': 60.0}], [('AAA$03d', 4), {'error': 'ratio'}], [('A+3d', 2), {'error': 'start-stop'}], [('a3/AC', 3), {'error': 'start-stop'}], [('A/59$T', 3), {'error': 'start-stop'}], [('C773C', 1.5), {'error': 'ratio'}], [('CA', 3), {'modules': 27}]], [[('B957A', 2.5), {'modules': 57.0}], [('B53C', 2), {'modules': 41}], [('A$7:+d', 1.5), {'error': 'ratio'}], [('a+A', 4), {'error': 'ratio'}], [('a958$3C', 1.5), {'error': 'ratio'}], [('D5357T', 1.5), {'error': 'ratio'}], [('a5C', 2), {'error': 'start-stop'}], [('D5-B', 2.5), {'modules': 46.0}]], [[('A:5B', 2), {'modules': 42}], [('B$D', 2), {'modules': 31}], [('aT', 2.5), {'error': 'start-stop'}], [('D3$20d', 3), {'error': 'start-stop'}], [('C58d', 1.5), {'error': 'ratio'}], [('D/5:3B', 4), {'error': 'ratio'}], [('AA', 1.5), {'error': 'ratio'}], [('A1D', 3), {'modules': 39}]], [[('A-31A', 3), {'modules': 63}], [('A905C', 3), {'modules': 63}], [('aB', 3), {'error': 'start-stop'}], [('Cd', 2), {'error': 'start-stop'}], [('a/D', 3), {'error': 'start-stop'}], [('A117.T', 2.5), {'error': 'start-stop'}], [('aD', 3), {'error': 'start-stop'}], [('C55C', 3), {'modules': 51}]]]
labels = ["regression: intercharacter gaps", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: intercharacter gaps 0{'modules': 41}{'modules': 41}Passed
repair trap 1{'modules': 53}{'modules': 53}Passed
combined fault 2{'char': 'A', 'error': 'char'}{'char': 'A', 'error': 'char'}Passed
control 3{'char': 'E', 'error': 'char'}{'char': 'E', 'error': 'char'}Passed
control 4{'error': 'start-stop'}{'error': 'start-stop'}Passed
boundary 5{'error': 'start-stop'}{'error': 'start-stop'}Passed
boundary 6{'error': 'ratio'}{'error': 'ratio'}Passed
control 7{'modules': 75}{'modules': 75}Passed

SHA-256 / 925fd9b065a9dca93194fca673cdd4fc436c9f002fcbec444980c489e9ba9f23

Verification & scope

A deterministic bounded teaching model with a stipulated contract; it makes no claim of conformance to any published specification. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:49:45.670043+00:00.

Case digest / 5118721034c1d4d453b721334823a2bea9050cb71f9de7c35a5c5ce89246932b