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FA-47021 / Bounded deques / Open access

Full deque append rejection clears its lazy orientation flag · case 01

Full deque append rejection clears its lazy orientation flag.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Full deque append rejection clears its lazy orientation flag.

VERIFIED REPAIR

Restore the documented full orientation invariant in lazy-orientation.

Unsuccessful approach: The partial repair still applies the incorrect transition to an admitted boundary or multi-element case.

Case contract

A bounded deque stores physical values and a lazy reversed flag. Flip toggles orientation without moving storage; logical append and front-pop select the appropriate physical endpoint. Full append rejects.

Why this case matters

Controlled bounded deque implementation model with explicit storage and lifecycle observations.

1 / The failure

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

N = 1
observations = []
def solve(x):
    storage,reverse,op,value,cap=x
    logical=storage[::-1] if reverse else storage[:]
    if op=='flip':return [storage,not reverse,logical[::-1],None]
    if op=='push':
        if len(storage)==cap:return [storage,False,logical,'full']
        physical=[value]+storage if reverse else storage+[value]
        return [physical,reverse,logical+[value],None]
    if not storage:return [storage,reverse,logical,'empty']
    result=storage[:-1] if reverse else storage[1:]
    removed=storage[-1] if reverse else storage[0]
    remaining=result[::-1] if reverse else result[:]
    return [result,reverse,remaining,removed]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N,N+1,N+2],True,"pop",0,4]), {1: [[1, 2], True, [2, 1], 3], 2: [[2, 3], True, [3, 2], 4], 3: [[3, 4], True, [4, 3], 5], 4: [[4, 5], True, [5, 4], 6], 5: [[5, 6], True, [6, 5], 7]}[N])
check('1', solve([[N,N+1],True,"push",N+2,4]), {1: [[3, 1, 2], True, [2, 1, 3], None], 2: [[4, 2, 3], True, [3, 2, 4], None], 3: [[5, 3, 4], True, [4, 3, 5], None], 4: [[6, 4, 5], True, [5, 4, 6], None], 5: [[7, 5, 6], True, [6, 5, 7], None]}[N])
check('2', solve([[N,N+1],False,"flip",0,3]), {1: [[1, 2], True, [2, 1], None], 2: [[2, 3], True, [3, 2], None], 3: [[3, 4], True, [4, 3], None], 4: [[4, 5], True, [5, 4], None], 5: [[5, 6], True, [6, 5], None]}[N])
check('3', solve([[N,N+1],True,"flip",0,3]), {1: [[1, 2], False, [1, 2], None], 2: [[2, 3], False, [2, 3], None], 3: [[3, 4], False, [3, 4], None], 4: [[4, 5], False, [4, 5], None], 5: [[5, 6], False, [5, 6], None]}[N])
check('4', solve([[N],False,"push",N+1,1]), {1: [[1], False, [1], 'full'], 2: [[2], False, [2], 'full'], 3: [[3], False, [3], 'full'], 4: [[4], False, [4], 'full'], 5: [[5], False, [5], 'full']}[N])
check('5', solve([[],True,"pop",0,3]), {1: [[], True, [], 'empty'], 2: [[], True, [], 'empty'], 3: [[], True, [], 'empty'], 4: [[], True, [], 'empty'], 5: [[], True, [], 'empty']}[N])
check('6', solve([[N,N+1],False,"pop",0,3]), {1: [[2], False, [2], 1], 2: [[3], False, [3], 2], 3: [[4], False, [4], 3], 4: [[5], False, [5], 4], 5: [[6], False, [6], 5]}[N])
check('7', solve([[N],False,"push",N+1,3]), {1: [[1, 2], False, [1, 2], None], 2: [[2, 3], False, [2, 3], None], 3: [[3, 4], False, [3, 4], None], 4: [[4, 5], False, [4, 5], None], 5: [[5, 6], False, [5, 6], None]}[N])
check('full reversed rejection', solve([[N,N+1],True,'push',N+2,2]), [[N,N+1],True,[N+1,N],'full'])
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
0[[1, 2], True, [2, 1], 3][[1, 2], True, [2, 1], 3]Passed
1[[3, 1, 2], True, [2, 1, 3], None][[3, 1, 2], True, [2, 1, 3], None]Passed
2[[1, 2], True, [2, 1], None][[1, 2], True, [2, 1], None]Passed
3[[1, 2], False, [1, 2], None][[1, 2], False, [1, 2], None]Passed
4[[1], False, [1], 'full'][[1], False, [1], 'full']Passed
5[[], True, [], 'empty'][[], True, [], 'empty']Passed
6[[2], False, [2], 1][[2], False, [2], 1]Passed
7[[1, 2], False, [1, 2], None][[1, 2], False, [1, 2], None]Passed
full reversed rejection[[1, 2], False, [2, 1], 'full'][[1, 2], True, [2, 1], 'full']Failed

SHA-256 / 50ed0eb1a6e36db2ee36bc16461771d315dba0ed66be812613dcf017767a5332

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    storage,reverse,op,value,cap=x
    logical=storage[::-1] if reverse else storage[:]
    if op=='flip':return [storage,not reverse,logical[::-1],None]
    if op=='push':
        if len(storage)==cap:return [storage,False if storage else reverse,logical,'full']
        physical=[value]+storage if reverse else storage+[value]
        return [physical,reverse,logical+[value],None]
    if not storage:return [storage,reverse,logical,'empty']
    result=storage[:-1] if reverse else storage[1:]
    removed=storage[-1] if reverse else storage[0]
    remaining=result[::-1] if reverse else result[:]
    return [result,reverse,remaining,removed]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N,N+1,N+2],True,"pop",0,4]), {1: [[1, 2], True, [2, 1], 3], 2: [[2, 3], True, [3, 2], 4], 3: [[3, 4], True, [4, 3], 5], 4: [[4, 5], True, [5, 4], 6], 5: [[5, 6], True, [6, 5], 7]}[N])
check('1', solve([[N,N+1],True,"push",N+2,4]), {1: [[3, 1, 2], True, [2, 1, 3], None], 2: [[4, 2, 3], True, [3, 2, 4], None], 3: [[5, 3, 4], True, [4, 3, 5], None], 4: [[6, 4, 5], True, [5, 4, 6], None], 5: [[7, 5, 6], True, [6, 5, 7], None]}[N])
check('2', solve([[N,N+1],False,"flip",0,3]), {1: [[1, 2], True, [2, 1], None], 2: [[2, 3], True, [3, 2], None], 3: [[3, 4], True, [4, 3], None], 4: [[4, 5], True, [5, 4], None], 5: [[5, 6], True, [6, 5], None]}[N])
check('3', solve([[N,N+1],True,"flip",0,3]), {1: [[1, 2], False, [1, 2], None], 2: [[2, 3], False, [2, 3], None], 3: [[3, 4], False, [3, 4], None], 4: [[4, 5], False, [4, 5], None], 5: [[5, 6], False, [5, 6], None]}[N])
check('4', solve([[N],False,"push",N+1,1]), {1: [[1], False, [1], 'full'], 2: [[2], False, [2], 'full'], 3: [[3], False, [3], 'full'], 4: [[4], False, [4], 'full'], 5: [[5], False, [5], 'full']}[N])
check('5', solve([[],True,"pop",0,3]), {1: [[], True, [], 'empty'], 2: [[], True, [], 'empty'], 3: [[], True, [], 'empty'], 4: [[], True, [], 'empty'], 5: [[], True, [], 'empty']}[N])
check('6', solve([[N,N+1],False,"pop",0,3]), {1: [[2], False, [2], 1], 2: [[3], False, [3], 2], 3: [[4], False, [4], 3], 4: [[5], False, [5], 4], 5: [[6], False, [6], 5]}[N])
check('7', solve([[N],False,"push",N+1,3]), {1: [[1, 2], False, [1, 2], None], 2: [[2, 3], False, [2, 3], None], 3: [[3, 4], False, [3, 4], None], 4: [[4, 5], False, [4, 5], None], 5: [[5, 6], False, [5, 6], None]}[N])
check('full reversed rejection', solve([[N,N+1],True,'push',N+2,2]), [[N,N+1],True,[N+1,N],'full'])
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
0[[1, 2], True, [2, 1], 3][[1, 2], True, [2, 1], 3]Passed
1[[3, 1, 2], True, [2, 1, 3], None][[3, 1, 2], True, [2, 1, 3], None]Passed
2[[1, 2], True, [2, 1], None][[1, 2], True, [2, 1], None]Passed
3[[1, 2], False, [1, 2], None][[1, 2], False, [1, 2], None]Passed
4[[1], False, [1], 'full'][[1], False, [1], 'full']Passed
5[[], True, [], 'empty'][[], True, [], 'empty']Passed
6[[2], False, [2], 1][[2], False, [2], 1]Passed
7[[1, 2], False, [1, 2], None][[1, 2], False, [1, 2], None]Passed
full reversed rejection[[1, 2], False, [2, 1], 'full'][[1, 2], True, [2, 1], 'full']Failed

SHA-256 / 008ccab510447836e263153babfa4ef3eff3141f82f71c4bd230c882aee8b2e6

3 / The verified repair

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

N = 1
observations = []
def solve(x):
    storage,reverse,op,value,cap=x
    logical=storage[::-1] if reverse else storage[:]
    if op=='flip':return [storage,not reverse,logical[::-1],None]
    if op=='push':
        if len(storage)==cap:return [storage,reverse,logical,'full']
        physical=[value]+storage if reverse else storage+[value]
        return [physical,reverse,logical+[value],None]
    if not storage:return [storage,reverse,logical,'empty']
    result=storage[:-1] if reverse else storage[1:]
    removed=storage[-1] if reverse else storage[0]
    remaining=result[::-1] if reverse else result[:]
    return [result,reverse,remaining,removed]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N,N+1,N+2],True,"pop",0,4]), {1: [[1, 2], True, [2, 1], 3], 2: [[2, 3], True, [3, 2], 4], 3: [[3, 4], True, [4, 3], 5], 4: [[4, 5], True, [5, 4], 6], 5: [[5, 6], True, [6, 5], 7]}[N])
check('1', solve([[N,N+1],True,"push",N+2,4]), {1: [[3, 1, 2], True, [2, 1, 3], None], 2: [[4, 2, 3], True, [3, 2, 4], None], 3: [[5, 3, 4], True, [4, 3, 5], None], 4: [[6, 4, 5], True, [5, 4, 6], None], 5: [[7, 5, 6], True, [6, 5, 7], None]}[N])
check('2', solve([[N,N+1],False,"flip",0,3]), {1: [[1, 2], True, [2, 1], None], 2: [[2, 3], True, [3, 2], None], 3: [[3, 4], True, [4, 3], None], 4: [[4, 5], True, [5, 4], None], 5: [[5, 6], True, [6, 5], None]}[N])
check('3', solve([[N,N+1],True,"flip",0,3]), {1: [[1, 2], False, [1, 2], None], 2: [[2, 3], False, [2, 3], None], 3: [[3, 4], False, [3, 4], None], 4: [[4, 5], False, [4, 5], None], 5: [[5, 6], False, [5, 6], None]}[N])
check('4', solve([[N],False,"push",N+1,1]), {1: [[1], False, [1], 'full'], 2: [[2], False, [2], 'full'], 3: [[3], False, [3], 'full'], 4: [[4], False, [4], 'full'], 5: [[5], False, [5], 'full']}[N])
check('5', solve([[],True,"pop",0,3]), {1: [[], True, [], 'empty'], 2: [[], True, [], 'empty'], 3: [[], True, [], 'empty'], 4: [[], True, [], 'empty'], 5: [[], True, [], 'empty']}[N])
check('6', solve([[N,N+1],False,"pop",0,3]), {1: [[2], False, [2], 1], 2: [[3], False, [3], 2], 3: [[4], False, [4], 3], 4: [[5], False, [5], 4], 5: [[6], False, [6], 5]}[N])
check('7', solve([[N],False,"push",N+1,3]), {1: [[1, 2], False, [1, 2], None], 2: [[2, 3], False, [2, 3], None], 3: [[3, 4], False, [3, 4], None], 4: [[4, 5], False, [4, 5], None], 5: [[5, 6], False, [5, 6], None]}[N])
check('full reversed rejection', solve([[N,N+1],True,'push',N+2,2]), [[N,N+1],True,[N+1,N],'full'])
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
0[[1, 2], True, [2, 1], 3][[1, 2], True, [2, 1], 3]Passed
1[[3, 1, 2], True, [2, 1, 3], None][[3, 1, 2], True, [2, 1, 3], None]Passed
2[[1, 2], True, [2, 1], None][[1, 2], True, [2, 1], None]Passed
3[[1, 2], False, [1, 2], None][[1, 2], False, [1, 2], None]Passed
4[[1], False, [1], 'full'][[1], False, [1], 'full']Passed
5[[], True, [], 'empty'][[], True, [], 'empty']Passed
6[[2], False, [2], 1][[2], False, [2], 1]Passed
7[[1, 2], False, [1, 2], None][[1, 2], False, [1, 2], None]Passed
full reversed rejection[[1, 2], True, [2, 1], 'full'][[1, 2], True, [2, 1], 'full']Passed

SHA-256 / 7717b8a00c3961ff1a3605d14928e172f7e050412a6cf1e267e97d35211f64d0

Verification & scope

Offline finite deterministic model; no claim of production implementation or concurrent memory-model conformance. 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 2026-09-29T14:44:37.584004+00:00.

Case digest / 05949ee98537baa66697ce3217628059812d047731df00ae5e4d52b0a5cc8ed0