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FA-97461 / Knitting and sewing pattern grading / Open access

Pattern row locator: row origin guard · case 01

Row 0 is accepted as setup row 0.

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

ROOT CAUSE

Row 0 passes the guard although rows are 1-based.

THE FAILURE

Row 0 passes the guard although rows are 1-based.

Unsuccessful approach: Rejecting only when there is no setup still accepts row 0.

Case contract

Rows are 1-based. Rows 1..setup are ["setup", row]. The next length*repeats rows are ["repeat", repeat_number, row_in_repeat] (both 1-based). Later rows are ["finishing", k] counting from 1 after the last repeat. row < 1 -> "error: rows start at 1".

Why this case matters

Row counter apps must map an absolute row number onto setup, repeat and finishing sections.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(row, setup, length, repeats):
    if row < 0:
        return 'error: rows start at 1'
    if row <= setup:
        return ['setup', row]
    k = row - setup
    if k <= length * repeats:
        return ['repeat', (k - 1) // length + 1, (k - 1) % length + 1]
    return ['finishing', k - length * repeats]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['last setup row', [4, 4, 8, 3], ['setup', 4]], ['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]],
  ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['regression: row origin guard', [0, 1, 6, 5], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 1, 12, 3], 'error: rows start at 1'],
  ['generated control 1', [12, 0, 6, 2], ['repeat', 2, 6]],
  ['generated control 2', [9, 1, 6, 2], ['repeat', 2, 2]],
  ['generated control 3', [15, 6, 1, 5], ['finishing', 4]]],
 [['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]], ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['regression: row origin guard', [0, 4, 4, 5], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 2, 8, 1], 'error: rows start at 1'],
  ['generated control 1', [54, 1, 1, 3], ['finishing', 50]],
  ['generated control 2', [50, 2, 12, 3], ['finishing', 12]],
  ['generated control 3', [27, 2, 12, 5], ['repeat', 3, 1]]],
 [['single setup row', [1, 1, 4, 2], ['setup', 1]], ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['regression: row origin guard', [0, 2, 6, 2], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 1, 6, 1], 'error: rows start at 1'],
  ['generated control 1', [33, 4, 8, 3], ['finishing', 5]],
  ['generated control 2', [44, 1, 1, 2], ['finishing', 41]],
  ['generated control 3', [1, 0, 1, 2], ['repeat', 1, 1]]],
 [['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'],
  ['regression: row origin guard', [0, 1, 1, 5], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 4, 8, 5], 'error: rows start at 1'],
  ['generated control 1', [30, 6, 12, 3], ['repeat', 2, 12]],
  ['generated control 2', [57, 6, 8, 5], ['finishing', 11]],
  ['generated control 3', [57, 4, 1, 3], ['finishing', 50]]],
 [['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'], ['last setup row', [4, 4, 8, 3], ['setup', 4]],
  ['regression: row origin guard', [0, 4, 8, 1], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 2, 6, 3], 'error: rows start at 1'],
  ['generated control 1', [37, 1, 12, 3], ['repeat', 3, 12]],
  ['generated control 2', [23, 0, 6, 5], ['repeat', 4, 5]],
  ['generated control 3', [28, 6, 12, 1], ['finishing', 10]]]]
for label, args, expected in fixtures[N - 1]:
    check(label, 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
last setup row['setup', 4]['setup', 4]Passed
first repeat row['repeat', 1, 1]['repeat', 1, 1]Passed
single setup row['setup', 1]['setup', 1]Passed
regression: row origin guard['setup', 0]error: rows start at 1Failed
repair check: row origin guard['setup', 0]error: rows start at 1Failed
generated control 1['repeat', 2, 6]['repeat', 2, 6]Passed
generated control 2['repeat', 2, 2]['repeat', 2, 2]Passed
generated control 3['finishing', 4]['finishing', 4]Passed

SHA-256 / 725b6d0b4222bc5097e306496283c5546d7a8b188b635594ff9ccea6650f21c4

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(row, setup, length, repeats):
    if row < 1 and setup == 0:
        return 'error: rows start at 1'
    if row <= setup:
        return ['setup', row]
    k = row - setup
    if k <= length * repeats:
        return ['repeat', (k - 1) // length + 1, (k - 1) % length + 1]
    return ['finishing', k - length * repeats]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['last setup row', [4, 4, 8, 3], ['setup', 4]], ['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]],
  ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['regression: row origin guard', [0, 1, 6, 5], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 1, 12, 3], 'error: rows start at 1'],
  ['generated control 1', [12, 0, 6, 2], ['repeat', 2, 6]],
  ['generated control 2', [9, 1, 6, 2], ['repeat', 2, 2]],
  ['generated control 3', [15, 6, 1, 5], ['finishing', 4]]],
 [['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]], ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['regression: row origin guard', [0, 4, 4, 5], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 2, 8, 1], 'error: rows start at 1'],
  ['generated control 1', [54, 1, 1, 3], ['finishing', 50]],
  ['generated control 2', [50, 2, 12, 3], ['finishing', 12]],
  ['generated control 3', [27, 2, 12, 5], ['repeat', 3, 1]]],
 [['single setup row', [1, 1, 4, 2], ['setup', 1]], ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['regression: row origin guard', [0, 2, 6, 2], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 1, 6, 1], 'error: rows start at 1'],
  ['generated control 1', [33, 4, 8, 3], ['finishing', 5]],
  ['generated control 2', [44, 1, 1, 2], ['finishing', 41]],
  ['generated control 3', [1, 0, 1, 2], ['repeat', 1, 1]]],
 [['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'],
  ['regression: row origin guard', [0, 1, 1, 5], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 4, 8, 5], 'error: rows start at 1'],
  ['generated control 1', [30, 6, 12, 3], ['repeat', 2, 12]],
  ['generated control 2', [57, 6, 8, 5], ['finishing', 11]],
  ['generated control 3', [57, 4, 1, 3], ['finishing', 50]]],
 [['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'], ['last setup row', [4, 4, 8, 3], ['setup', 4]],
  ['regression: row origin guard', [0, 4, 8, 1], 'error: rows start at 1'],
  ['repair check: row origin guard', [0, 2, 6, 3], 'error: rows start at 1'],
  ['generated control 1', [37, 1, 12, 3], ['repeat', 3, 12]],
  ['generated control 2', [23, 0, 6, 5], ['repeat', 4, 5]],
  ['generated control 3', [28, 6, 12, 1], ['finishing', 10]]]]
for label, args, expected in fixtures[N - 1]:
    check(label, 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
last setup row['setup', 4]['setup', 4]Passed
first repeat row['repeat', 1, 1]['repeat', 1, 1]Passed
single setup row['setup', 1]['setup', 1]Passed
regression: row origin guard['setup', 0]error: rows start at 1Failed
repair check: row origin guard['setup', 0]error: rows start at 1Failed
generated control 1['repeat', 2, 6]['repeat', 2, 6]Passed
generated control 2['repeat', 2, 2]['repeat', 2, 2]Passed
generated control 3['finishing', 4]['finishing', 4]Passed

SHA-256 / 31ee4a274923f3ac26264c5970d93e0d72f6008cfc78c6016556dd8a5069db47

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic toy contract stated in full here; it is a bounded teaching model, not an authoritative reference or standards implementation. 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 2026-09-29T14:52:32.420256+00:00.

Case digest / 765ae47a47e2e01900e933303a1e0d5d9ae7865e1aff0f6cb00e21321b17f12b