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FA-97441 / Knitting and sewing pattern grading / Open access

Pattern row locator: repeat number · case 01

The last row of repeat 1 is reported as repeat 2.

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

ROOT CAUSE

The repeat number divides the 1-based offset without shifting it to 0-based.

VERIFIED REPAIR

Use (k-1)//length + 1.

Unsuccessful approach: k//length reports repeat 0 for the first rows.

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 < 1:
        return 'error: rows start at 1'
    if row <= setup:
        return ['setup', row]
    k = row - setup
    if k <= length * repeats:
        return ['repeat', k // 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: repeat number', [54, 6, 12, 5], ['repeat', 4, 12]],
  ['repair check: repeat number', [21, 0, 8, 3], ['repeat', 3, 5]],
  ['generated control 1', [32, 1, 6, 1], ['finishing', 25]],
  ['generated control 2', [19, 2, 6, 2], ['finishing', 5]],
  ['generated control 3', [43, 0, 12, 1], ['finishing', 31]]],
 [['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: repeat number', [16, 4, 4, 3], ['repeat', 3, 4]],
  ['repair check: repeat number', [1, 0, 6, 2], ['repeat', 1, 1]],
  ['generated control 1', [41, 6, 6, 1], ['finishing', 29]],
  ['generated control 2', [19, 0, 8, 1], ['finishing', 11]],
  ['generated control 3', [29, 6, 8, 3], ['repeat', 3, 7]]],
 [['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: repeat number', [7, 6, 1, 1], ['repeat', 1, 1]],
  ['repair check: repeat number', [23, 1, 12, 2], ['repeat', 2, 10]],
  ['generated control 1', [58, 0, 4, 1], ['finishing', 54]],
  ['generated control 2', [27, 6, 1, 3], ['finishing', 18]],
  ['generated control 3', [0, 4, 4, 5], 'error: rows start at 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: repeat number', [12, 4, 4, 5], ['repeat', 2, 4]],
  ['repair check: repeat number', [12, 6, 8, 2], ['repeat', 1, 6]],
  ['generated control 1', [37, 2, 12, 1], ['finishing', 23]],
  ['generated control 2', [60, 1, 1, 5], ['finishing', 54]],
  ['generated control 3', [24, 0, 6, 3], ['finishing', 6]]],
 [['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: repeat number', [14, 6, 8, 1], ['repeat', 1, 8]],
  ['repair check: repeat number', [15, 4, 8, 2], ['repeat', 2, 3]],
  ['generated control 1', [53, 4, 6, 1], ['finishing', 43]],
  ['generated control 2', [42, 1, 1, 5], ['finishing', 36]],
  ['generated control 3', [21, 6, 12, 3], ['repeat', 2, 3]]]]
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: repeat number['repeat', 5, 12]['repeat', 4, 12]Failed
repair check: repeat number['repeat', 3, 5]['repeat', 3, 5]Passed
generated control 1['finishing', 25]['finishing', 25]Passed
generated control 2['finishing', 5]['finishing', 5]Passed
generated control 3['finishing', 31]['finishing', 31]Passed

SHA-256 / 6a115a14ac7b9eb107dc21fa39f4406cdf23f526890ae7d99b19d0e048a3b1a9

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:
        return 'error: rows start at 1'
    if row <= setup:
        return ['setup', row]
    k = row - setup
    if k <= length * repeats:
        return ['repeat', k // length, (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: repeat number', [54, 6, 12, 5], ['repeat', 4, 12]],
  ['repair check: repeat number', [21, 0, 8, 3], ['repeat', 3, 5]],
  ['generated control 1', [32, 1, 6, 1], ['finishing', 25]],
  ['generated control 2', [19, 2, 6, 2], ['finishing', 5]],
  ['generated control 3', [43, 0, 12, 1], ['finishing', 31]]],
 [['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: repeat number', [16, 4, 4, 3], ['repeat', 3, 4]],
  ['repair check: repeat number', [1, 0, 6, 2], ['repeat', 1, 1]],
  ['generated control 1', [41, 6, 6, 1], ['finishing', 29]],
  ['generated control 2', [19, 0, 8, 1], ['finishing', 11]],
  ['generated control 3', [29, 6, 8, 3], ['repeat', 3, 7]]],
 [['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: repeat number', [7, 6, 1, 1], ['repeat', 1, 1]],
  ['repair check: repeat number', [23, 1, 12, 2], ['repeat', 2, 10]],
  ['generated control 1', [58, 0, 4, 1], ['finishing', 54]],
  ['generated control 2', [27, 6, 1, 3], ['finishing', 18]],
  ['generated control 3', [0, 4, 4, 5], 'error: rows start at 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: repeat number', [12, 4, 4, 5], ['repeat', 2, 4]],
  ['repair check: repeat number', [12, 6, 8, 2], ['repeat', 1, 6]],
  ['generated control 1', [37, 2, 12, 1], ['finishing', 23]],
  ['generated control 2', [60, 1, 1, 5], ['finishing', 54]],
  ['generated control 3', [24, 0, 6, 3], ['finishing', 6]]],
 [['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: repeat number', [14, 6, 8, 1], ['repeat', 1, 8]],
  ['repair check: repeat number', [15, 4, 8, 2], ['repeat', 2, 3]],
  ['generated control 1', [53, 4, 6, 1], ['finishing', 43]],
  ['generated control 2', [42, 1, 1, 5], ['finishing', 36]],
  ['generated control 3', [21, 6, 12, 3], ['repeat', 2, 3]]]]
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', 0, 1]['repeat', 1, 1]Failed
single setup row['setup', 1]['setup', 1]Passed
regression: repeat number['repeat', 4, 12]['repeat', 4, 12]Passed
repair check: repeat number['repeat', 2, 5]['repeat', 3, 5]Failed
generated control 1['finishing', 25]['finishing', 25]Passed
generated control 2['finishing', 5]['finishing', 5]Passed
generated control 3['finishing', 31]['finishing', 31]Passed

SHA-256 / 418b714e4c63105631d1421f4f08e642c0f22c7eeaf6ec50ef04b8454acbcd17

3 / The verified repair

Exit 0
"""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:
        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: repeat number', [54, 6, 12, 5], ['repeat', 4, 12]],
  ['repair check: repeat number', [21, 0, 8, 3], ['repeat', 3, 5]],
  ['generated control 1', [32, 1, 6, 1], ['finishing', 25]],
  ['generated control 2', [19, 2, 6, 2], ['finishing', 5]],
  ['generated control 3', [43, 0, 12, 1], ['finishing', 31]]],
 [['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: repeat number', [16, 4, 4, 3], ['repeat', 3, 4]],
  ['repair check: repeat number', [1, 0, 6, 2], ['repeat', 1, 1]],
  ['generated control 1', [41, 6, 6, 1], ['finishing', 29]],
  ['generated control 2', [19, 0, 8, 1], ['finishing', 11]],
  ['generated control 3', [29, 6, 8, 3], ['repeat', 3, 7]]],
 [['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: repeat number', [7, 6, 1, 1], ['repeat', 1, 1]],
  ['repair check: repeat number', [23, 1, 12, 2], ['repeat', 2, 10]],
  ['generated control 1', [58, 0, 4, 1], ['finishing', 54]],
  ['generated control 2', [27, 6, 1, 3], ['finishing', 18]],
  ['generated control 3', [0, 4, 4, 5], 'error: rows start at 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: repeat number', [12, 4, 4, 5], ['repeat', 2, 4]],
  ['repair check: repeat number', [12, 6, 8, 2], ['repeat', 1, 6]],
  ['generated control 1', [37, 2, 12, 1], ['finishing', 23]],
  ['generated control 2', [60, 1, 1, 5], ['finishing', 54]],
  ['generated control 3', [24, 0, 6, 3], ['finishing', 6]]],
 [['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: repeat number', [14, 6, 8, 1], ['repeat', 1, 8]],
  ['repair check: repeat number', [15, 4, 8, 2], ['repeat', 2, 3]],
  ['generated control 1', [53, 4, 6, 1], ['finishing', 43]],
  ['generated control 2', [42, 1, 1, 5], ['finishing', 36]],
  ['generated control 3', [21, 6, 12, 3], ['repeat', 2, 3]]]]
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: repeat number['repeat', 4, 12]['repeat', 4, 12]Passed
repair check: repeat number['repeat', 3, 5]['repeat', 3, 5]Passed
generated control 1['finishing', 25]['finishing', 25]Passed
generated control 2['finishing', 5]['finishing', 5]Passed
generated control 3['finishing', 31]['finishing', 31]Passed

SHA-256 / 55029762ed1ac7dcbc0f7eaa8e8e88aeaf4029462874d8cdcefd0543e0e5e0af

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 2026-09-29T14:52:32.285869+00:00.

Case digest / 309b600111eb707c19d61a67fa62ef1c9b01d1c22b73e95d7de18b6177e982cc