FA-97486 / Knitting and sewing pattern grading / Open access

Knitting chart row reader: repeated special stitch · case 01

Two consecutive yarn overs print as a single "yo".

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ROOT CAUSE

Runs of non-knit/purl stitches drop their count.

THE FAILURE

Runs of non-knit/purl stitches drop their count.

Unsuccessful approach: Always printing a count shows "yo x1" for a single yarn over.

Case contract

chart rows are listed bottom-up (row 1 first), cells left-to-right as drawn. Rounds and RS rows read right-to-left unchanged. Flat WS rows (even rows, or odd rows when start_ws) read left-to-right with swaps k<->p, k2tog->p2tog, ssk->ssp, yo stays. Runs of identical stitches merge: k/p as "k3", others as "yo" or "yo x2". Row outside 1..len -> error.

Why this case matters

Chart readers must flip reading direction and stitch meaning on wrong-side rows.

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(chart, row, in_round, start_ws):
    SWAP = {'k': 'p', 'p': 'k', 'k2tog': 'p2tog', 'ssk': 'ssp', 'yo': 'yo'}
    if not 1 <= row <= len(chart):
        return 'error: no such row'
    cells = list(chart[row - 1])
    ws = (not in_round) and ((row % 2 == 0) != start_ws)
    if ws:
        seq = [SWAP.get(c, c) for c in cells]
    else:
        seq = cells[::-1]
    out = []
    for c in seq:
        if out and out[-1][0] == c:
            out[-1][1] += 1
        else:
            out.append([c, 1])
    return ', '.join(c + str(n) if c in ('k', 'p') else c for c, n in out)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['regression: repeated special stitch',
   [[['yo', 'k', 'yo', 'k', 'yo', 'yo'], ['p', 'k', 'ssk', 'yo', 'p', 'k'],
     ['yo', 'yo', 'yo', 'k', 'yo', 'yo']],
    3, False, False],
   'yo x2, k1, yo x3'],
  ['repair check: repeated special stitch',
   [[['k', 'k', 'yo', 'yo', 'ssk', 'k'], ['k', 'p', 'k', 'ssk', 'k2tog', 'k']], 2, False, False],
   'p1, k1, p1, ssp, p2tog, p1'],
  ['generated control 1',
   [[['yo', 'k', 'p', 'k', 'yo', 'yo'], ['k2tog', 'p', 'ssk', 'k', 'yo', 'k2tog'],
     ['k', 'ssk', 'yo', 'ssk', 'yo', 'yo'], ['ssk', 'k', 'p', 'yo', 'k', 'p'],
     ['k2tog', 'yo', 'k2tog', 'k2tog', 'yo', 'ssk']],
    1, False, False],
   'yo x2, k1, p1, k1, yo'],
  ['generated control 2',
   [[['yo', 'p', 'yo', 'k2tog', 'yo', 'k', 'yo', 'yo'],
     ['k2tog', 'k2tog', 'k2tog', 'p', 'k2tog', 'ssk', 'k2tog', 'ssk'],
     ['ssk', 'k', 'k', 'yo', 'ssk', 'p', 'k2tog', 'p'], ['k', 'k2tog', 'k2tog', 'p', 'k', 'p', 'p', 'k2tog'],
     ['k', 'yo', 'k2tog', 'k2tog', 'p', 'k2tog', 'p', 'yo']],
    2, False, False],
   'p2tog x3, k1, p2tog, ssp, p2tog, ssp'],
  ['generated control 3',
   [[['yo', 'yo', 'k2tog'], ['p', 'yo', 'k'], ['ssk', 'ssk', 'k2tog'], ['k', 'yo', 'ssk'], ['p', 'k', 'yo'],
     ['p', 'p', 'yo']],
    6, False, False],
   'k2, yo']],
 [['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['out of range', [[['k']], 3, False, False], 'error: no such row'],
  ['regression: repeated special stitch',
   [[['k', 'p', 'p', 'yo', 'k2tog', 'k2tog', 'k2tog', 'k2tog'],
     ['k2tog', 'yo', 'yo', 'ssk', 'ssk', 'yo', 'yo', 'k2tog'],
     ['k2tog', 'k2tog', 'k2tog', 'p', 'k', 'p', 'yo', 'k2tog']],
    1, True, False],
   'k2tog x4, yo, p2, k1'],
  ['repair check: repeated special stitch',
   [[['ssk', 'p', 'k', 'ssk', 'yo', 'k2tog', 'k2tog', 'k2tog'],
     ['p', 'ssk', 'ssk', 'k', 'k2tog', 'p', 'p', 'yo'], ['p', 'ssk', 'p', 'ssk', 'ssk', 'ssk', 'yo', 'yo']],
    1, False, False],
   'k2tog x3, yo, ssk, k1, p1, ssk'],
  ['generated control 1',
   [[['yo', 'yo', 'k2tog'], ['k', 'p', 'ssk'], ['k2tog', 'k2tog', 'p']], 1, False, False], 'k2tog, yo x2'],
  ['generated control 2',
   [[['yo', 'p', 'k2tog', 'yo', 'yo', 'yo', 'k2tog', 'ssk'],
     ['p', 'ssk', 'k2tog', 'p', 'ssk', 'p', 'k2tog', 'k2tog'],
     ['p', 'p', 'ssk', 'p', 'ssk', 'p', 'yo', 'k']],
    3, True, True],
   'k1, yo, p1, ssk, p1, ssk, p2'],
  ['generated control 3',
   [[['k', 'k', 'p', 'yo', 'yo', 'ssk', 'ssk', 'k2tog'],
     ['ssk', 'yo', 'k2tog', 'p', 'k2tog', 'k', 'ssk', 'yo']],
    2, False, False],
   'ssp, yo, p2tog, k1, p2tog, p1, ssp, yo']],
 [['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['out of range', [[['k']], 3, False, False], 'error: no such row'],
  ['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['regression: repeated special stitch',
   [[['k', 'ssk', 'ssk', 'ssk', 'ssk', 'p', 'k'], ['ssk', 'k', 'yo', 'k', 'yo', 'p', 'ssk'],
     ['yo', 'k', 'ssk', 'p', 'k2tog', 'ssk', 'yo']],
    1, True, False],
   'k1, p1, ssk x4, k1'],
  ['repair check: repeated special stitch',
   [[['k2tog', 'yo', 'k2tog', 'ssk', 'k2tog', 'p', 'k2tog'], ['k', 'yo', 'k2tog', 'ssk', 'p', 'yo', 'p']], 2,
    False, True],
   'p1, yo, p1, ssk, k2tog, yo, k1'],
  ['generated control 1', [[['k2tog', 'p', 'ssk'], ['k', 'p', 'ssk'], ['p', 'k', 'p']], 3, False, False],
   'p1, k1, p1'],
  ['generated control 2', [[['p', 'p', 'k'], ['yo', 'k', 'k']], 1, False, False], 'k1, p2'],
  ['generated control 3',
   [[['k2tog', 'yo', 'yo', 'k'], ['k', 'k', 'ssk', 'yo'], ['ssk', 'ssk', 'p', 'k2tog'],
     ['k', 'k2tog', 'ssk', 'p'], ['p', 'p', 'ssk', 'k'], ['k', 'k2tog', 'yo', 'p']],
    5, True, False],
   'k1, ssk, p2']],
 [['out of range', [[['k']], 3, False, False], 'error: no such row'],
  ['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['regression: repeated special stitch',
   [[['yo', 'k2tog', 'k2tog', 'ssk', 'k', 'p', 'ssk', 'ssk'], ['k', 'k', 'ssk', 'p', 'k2tog', 'k', 'p', 'p'],
     ['ssk', 'k', 'k2tog', 'yo', 'yo', 'yo', 'ssk', 'k2tog']],
    3, False, False],
   'k2tog, ssk, yo x3, k2tog, k1, ssk'],
  ['repair check: repeated special stitch',
   [[['ssk', 'p', 'ssk', 'k2tog'], ['ssk', 'p', 'yo', 'k2tog']], 1, False, True], 'ssp, k1, ssp, p2tog'],
  ['generated control 1',
   [[['yo', 'yo', 'yo', 'k2tog'], ['k2tog', 'ssk', 'k2tog', 'k'], ['yo', 'yo', 'k', 'k'],
     ['k2tog', 'yo', 'k2tog', 'k'], ['k2tog', 'k2tog', 'p', 'k2tog']],
    4, True, True],
   'k1, k2tog, yo, k2tog'],
  ['generated control 2',
   [[['p', 'k2tog', 'k', 'ssk', 'k2tog', 'yo', 'yo'], ['ssk', 'p', 'ssk', 'ssk', 'yo', 'k2tog', 'ssk'],
     ['yo', 'p', 'yo', 'yo', 'ssk', 'k', 'k'], ['k', 'k', 'k', 'k', 'k2tog', 'yo', 'k']],
    4, False, True],
   'k1, yo, k2tog, k4'],
  ['generated control 3',
   [[['p', 'yo', 'yo', 'k', 'yo', 'yo'], ['k', 'ssk', 'yo', 'yo', 'k', 'p'],
     ['k2tog', 'k2tog', 'yo', 'ssk', 'yo', 'ssk'], ['p', 'ssk', 'yo', 'k2tog', 'k', 'k2tog']],
    4, True, False],
   'k2tog, k1, k2tog, yo, ssk, p1']],
 [['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['regression: repeated special stitch',
   [[['yo', 'yo', 'k', 'k2tog', 'ssk'], ['k2tog', 'k2tog', 'k', 'k', 'k2tog'],
     ['k2tog', 'k', 'k', 'p', 'ssk'], ['p', 'p', 'k2tog', 'k2tog', 'k'], ['yo', 'yo', 'ssk', 'p', 'p'],
     ['p', 'yo', 'p', 'yo', 'k2tog']],
    5, True, False],
   'p2, ssk, yo x2'],
  ['repair check: repeated special stitch',
   [[['k2tog', 'yo', 'k2tog'], ['yo', 'ssk', 'k2tog'], ['k', 'k', 'k2tog']], 1, True, False],
   'k2tog, yo, k2tog'],
  ['generated control 1',
   [[['k2tog', 'p', 'ssk', 'ssk', 'k', 'p'], ['yo', 'ssk', 'ssk', 'ssk', 'yo', 'k'],
     ['p', 'k', 'k2tog', 'ssk', 'p', 'k']],
    3, False, False],
   'k1, p1, ssk, k2tog, k1, p1'],
  ['generated control 2',
   [[['k', 'p', 'p', 'yo', 'yo', 'k2tog'], ['p', 'ssk', 'p', 'k', 'yo', 'p'],
     ['yo', 'ssk', 'k', 'yo', 'k', 'k2tog'], ['k', 'k2tog', 'ssk', 'k', 'yo', 'k2tog']],
    2, True, False],
   'p1, yo, k1, p1, ssk, p1'],
  ['generated control 3', [[['yo', 'k2tog', 'p'], ['yo', 'k2tog', 'k']], 1, False, True], 'yo, p2tog, k1']]]
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 fixture	Actual	Expected	Outcome
RS row	`k2tog, yo, p1, k2`	`k2tog, yo, p1, k2`	Passed
WS row swapped	`k2, p1, ssp, p1`	`k2, p1, ssp, p1`	Passed
in the round	`k1, ssk`	`k1, ssk`	Passed
regression: repeated special stitch	`yo, k1, yo`	`yo x2, k1, yo x3`	Failed
repair check: repeated special stitch	`p1, k1, p1, ssp, p2tog, p1`	`p1, k1, p1, ssp, p2tog, p1`	Passed
generated control 1	`yo, k1, p1, k1, yo`	`yo x2, k1, p1, k1, yo`	Failed
generated control 2	`p2tog, k1, p2tog, ssp, p2tog, ssp`	`p2tog x3, k1, p2tog, ssp, p2tog, ssp`	Failed
generated control 3	`k2, yo`	`k2, yo`	Passed

SHA-256 / bc0e08b6e348b576ccf579603b69d4c02120a6c67209aef4402edab8fe468d44

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(chart, row, in_round, start_ws):
    SWAP = {'k': 'p', 'p': 'k', 'k2tog': 'p2tog', 'ssk': 'ssp', 'yo': 'yo'}
    if not 1 <= row <= len(chart):
        return 'error: no such row'
    cells = list(chart[row - 1])
    ws = (not in_round) and ((row % 2 == 0) != start_ws)
    if ws:
        seq = [SWAP.get(c, c) for c in cells]
    else:
        seq = cells[::-1]
    out = []
    for c in seq:
        if out and out[-1][0] == c:
            out[-1][1] += 1
        else:
            out.append([c, 1])
    return ', '.join(c + str(n) if c in ('k', 'p') else '%s x%d' % (c, n) for c, n in out)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['regression: repeated special stitch',
   [[['yo', 'k', 'yo', 'k', 'yo', 'yo'], ['p', 'k', 'ssk', 'yo', 'p', 'k'],
     ['yo', 'yo', 'yo', 'k', 'yo', 'yo']],
    3, False, False],
   'yo x2, k1, yo x3'],
  ['repair check: repeated special stitch',
   [[['k', 'k', 'yo', 'yo', 'ssk', 'k'], ['k', 'p', 'k', 'ssk', 'k2tog', 'k']], 2, False, False],
   'p1, k1, p1, ssp, p2tog, p1'],
  ['generated control 1',
   [[['yo', 'k', 'p', 'k', 'yo', 'yo'], ['k2tog', 'p', 'ssk', 'k', 'yo', 'k2tog'],
     ['k', 'ssk', 'yo', 'ssk', 'yo', 'yo'], ['ssk', 'k', 'p', 'yo', 'k', 'p'],
     ['k2tog', 'yo', 'k2tog', 'k2tog', 'yo', 'ssk']],
    1, False, False],
   'yo x2, k1, p1, k1, yo'],
  ['generated control 2',
   [[['yo', 'p', 'yo', 'k2tog', 'yo', 'k', 'yo', 'yo'],
     ['k2tog', 'k2tog', 'k2tog', 'p', 'k2tog', 'ssk', 'k2tog', 'ssk'],
     ['ssk', 'k', 'k', 'yo', 'ssk', 'p', 'k2tog', 'p'], ['k', 'k2tog', 'k2tog', 'p', 'k', 'p', 'p', 'k2tog'],
     ['k', 'yo', 'k2tog', 'k2tog', 'p', 'k2tog', 'p', 'yo']],
    2, False, False],
   'p2tog x3, k1, p2tog, ssp, p2tog, ssp'],
  ['generated control 3',
   [[['yo', 'yo', 'k2tog'], ['p', 'yo', 'k'], ['ssk', 'ssk', 'k2tog'], ['k', 'yo', 'ssk'], ['p', 'k', 'yo'],
     ['p', 'p', 'yo']],
    6, False, False],
   'k2, yo']],
 [['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['out of range', [[['k']], 3, False, False], 'error: no such row'],
  ['regression: repeated special stitch',
   [[['k', 'p', 'p', 'yo', 'k2tog', 'k2tog', 'k2tog', 'k2tog'],
     ['k2tog', 'yo', 'yo', 'ssk', 'ssk', 'yo', 'yo', 'k2tog'],
     ['k2tog', 'k2tog', 'k2tog', 'p', 'k', 'p', 'yo', 'k2tog']],
    1, True, False],
   'k2tog x4, yo, p2, k1'],
  ['repair check: repeated special stitch',
   [[['ssk', 'p', 'k', 'ssk', 'yo', 'k2tog', 'k2tog', 'k2tog'],
     ['p', 'ssk', 'ssk', 'k', 'k2tog', 'p', 'p', 'yo'], ['p', 'ssk', 'p', 'ssk', 'ssk', 'ssk', 'yo', 'yo']],
    1, False, False],
   'k2tog x3, yo, ssk, k1, p1, ssk'],
  ['generated control 1',
   [[['yo', 'yo', 'k2tog'], ['k', 'p', 'ssk'], ['k2tog', 'k2tog', 'p']], 1, False, False], 'k2tog, yo x2'],
  ['generated control 2',
   [[['yo', 'p', 'k2tog', 'yo', 'yo', 'yo', 'k2tog', 'ssk'],
     ['p', 'ssk', 'k2tog', 'p', 'ssk', 'p', 'k2tog', 'k2tog'],
     ['p', 'p', 'ssk', 'p', 'ssk', 'p', 'yo', 'k']],
    3, True, True],
   'k1, yo, p1, ssk, p1, ssk, p2'],
  ['generated control 3',
   [[['k', 'k', 'p', 'yo', 'yo', 'ssk', 'ssk', 'k2tog'],
     ['ssk', 'yo', 'k2tog', 'p', 'k2tog', 'k', 'ssk', 'yo']],
    2, False, False],
   'ssp, yo, p2tog, k1, p2tog, p1, ssp, yo']],
 [['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['out of range', [[['k']], 3, False, False], 'error: no such row'],
  ['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['regression: repeated special stitch',
   [[['k', 'ssk', 'ssk', 'ssk', 'ssk', 'p', 'k'], ['ssk', 'k', 'yo', 'k', 'yo', 'p', 'ssk'],
     ['yo', 'k', 'ssk', 'p', 'k2tog', 'ssk', 'yo']],
    1, True, False],
   'k1, p1, ssk x4, k1'],
  ['repair check: repeated special stitch',
   [[['k2tog', 'yo', 'k2tog', 'ssk', 'k2tog', 'p', 'k2tog'], ['k', 'yo', 'k2tog', 'ssk', 'p', 'yo', 'p']], 2,
    False, True],
   'p1, yo, p1, ssk, k2tog, yo, k1'],
  ['generated control 1', [[['k2tog', 'p', 'ssk'], ['k', 'p', 'ssk'], ['p', 'k', 'p']], 3, False, False],
   'p1, k1, p1'],
  ['generated control 2', [[['p', 'p', 'k'], ['yo', 'k', 'k']], 1, False, False], 'k1, p2'],
  ['generated control 3',
   [[['k2tog', 'yo', 'yo', 'k'], ['k', 'k', 'ssk', 'yo'], ['ssk', 'ssk', 'p', 'k2tog'],
     ['k', 'k2tog', 'ssk', 'p'], ['p', 'p', 'ssk', 'k'], ['k', 'k2tog', 'yo', 'p']],
    5, True, False],
   'k1, ssk, p2']],
 [['out of range', [[['k']], 3, False, False], 'error: no such row'],
  ['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['regression: repeated special stitch',
   [[['yo', 'k2tog', 'k2tog', 'ssk', 'k', 'p', 'ssk', 'ssk'], ['k', 'k', 'ssk', 'p', 'k2tog', 'k', 'p', 'p'],
     ['ssk', 'k', 'k2tog', 'yo', 'yo', 'yo', 'ssk', 'k2tog']],
    3, False, False],
   'k2tog, ssk, yo x3, k2tog, k1, ssk'],
  ['repair check: repeated special stitch',
   [[['ssk', 'p', 'ssk', 'k2tog'], ['ssk', 'p', 'yo', 'k2tog']], 1, False, True], 'ssp, k1, ssp, p2tog'],
  ['generated control 1',
   [[['yo', 'yo', 'yo', 'k2tog'], ['k2tog', 'ssk', 'k2tog', 'k'], ['yo', 'yo', 'k', 'k'],
     ['k2tog', 'yo', 'k2tog', 'k'], ['k2tog', 'k2tog', 'p', 'k2tog']],
    4, True, True],
   'k1, k2tog, yo, k2tog'],
  ['generated control 2',
   [[['p', 'k2tog', 'k', 'ssk', 'k2tog', 'yo', 'yo'], ['ssk', 'p', 'ssk', 'ssk', 'yo', 'k2tog', 'ssk'],
     ['yo', 'p', 'yo', 'yo', 'ssk', 'k', 'k'], ['k', 'k', 'k', 'k', 'k2tog', 'yo', 'k']],
    4, False, True],
   'k1, yo, k2tog, k4'],
  ['generated control 3',
   [[['p', 'yo', 'yo', 'k', 'yo', 'yo'], ['k', 'ssk', 'yo', 'yo', 'k', 'p'],
     ['k2tog', 'k2tog', 'yo', 'ssk', 'yo', 'ssk'], ['p', 'ssk', 'yo', 'k2tog', 'k', 'k2tog']],
    4, True, False],
   'k2tog, k1, k2tog, yo, ssk, p1']],
 [['RS row', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'k', 'k']], 1, False, False],
   'k2tog, yo, p1, k2'],
  ['WS row swapped', [[['k', 'k', 'p', 'yo', 'k2tog'], ['p', 'p', 'k', 'ssk', 'k']], 2, False, False],
   'k2, p1, ssp, p1'],
  ['in the round', [[['k', 'p'], ['ssk', 'k']], 2, True, False], 'k1, ssk'],
  ['regression: repeated special stitch',
   [[['yo', 'yo', 'k', 'k2tog', 'ssk'], ['k2tog', 'k2tog', 'k', 'k', 'k2tog'],
     ['k2tog', 'k', 'k', 'p', 'ssk'], ['p', 'p', 'k2tog', 'k2tog', 'k'], ['yo', 'yo', 'ssk', 'p', 'p'],
     ['p', 'yo', 'p', 'yo', 'k2tog']],
    5, True, False],
   'p2, ssk, yo x2'],
  ['repair check: repeated special stitch',
   [[['k2tog', 'yo', 'k2tog'], ['yo', 'ssk', 'k2tog'], ['k', 'k', 'k2tog']], 1, True, False],
   'k2tog, yo, k2tog'],
  ['generated control 1',
   [[['k2tog', 'p', 'ssk', 'ssk', 'k', 'p'], ['yo', 'ssk', 'ssk', 'ssk', 'yo', 'k'],
     ['p', 'k', 'k2tog', 'ssk', 'p', 'k']],
    3, False, False],
   'k1, p1, ssk, k2tog, k1, p1'],
  ['generated control 2',
   [[['k', 'p', 'p', 'yo', 'yo', 'k2tog'], ['p', 'ssk', 'p', 'k', 'yo', 'p'],
     ['yo', 'ssk', 'k', 'yo', 'k', 'k2tog'], ['k', 'k2tog', 'ssk', 'k', 'yo', 'k2tog']],
    2, True, False],
   'p1, yo, k1, p1, ssk, p1'],
  ['generated control 3', [[['yo', 'k2tog', 'p'], ['yo', 'k2tog', 'k']], 1, False, True], 'yo, p2tog, k1']]]
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 fixture	Actual	Expected	Outcome
RS row	`k2tog x1, yo x1, p1, k2`	`k2tog, yo, p1, k2`	Failed
WS row swapped	`k2, p1, ssp x1, p1`	`k2, p1, ssp, p1`	Failed
in the round	`k1, ssk x1`	`k1, ssk`	Failed
regression: repeated special stitch	`yo x2, k1, yo x3`	`yo x2, k1, yo x3`	Passed
repair check: repeated special stitch	`p1, k1, p1, ssp x1, p2tog x1, p1`	`p1, k1, p1, ssp, p2tog, p1`	Failed
generated control 1	`yo x2, k1, p1, k1, yo x1`	`yo x2, k1, p1, k1, yo`	Failed
generated control 2	`p2tog x3, k1, p2tog x1, ssp x1, p2tog x1, ssp x1`	`p2tog x3, k1, p2tog, ssp, p2tog, ssp`	Failed
generated control 3	`k2, yo x1`	`k2, yo`	Failed

SHA-256 / 23584e426b1d30746504330e011845f52e480298c490591edc4ea9c2aad930a7

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 2026-09-29T14:52:32.657995+00:00.

Case digest / 609a4109681332761b45d0eae8ecc127e44d66d353930f88b113e06b5865cd7d