FA-81841 / Poker hand evaluation / Open access

Ace-low wheel never registers as a straight · case 01

A-2-3-4-5 is reported as high card and the steel wheel as a plain flush.

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

ROOT CAUSE

The wheel test compares the rank set against an ace valued 1, but the parser always values the ace at 14, so the branch is dead.

THE FAILURE

The wheel test compares the rank set against an ace valued 1, but the parser always values the ace at 14, so the branch is dead.

Unsuccessful approach: Matching only the four low ranks 2-3-4-5 accepts any fifth card, so 2-3-4-5-9 becomes a straight.

Case contract

Input: five distinct cards as rank+suit strings; ranks 2-9, T or 10, J, Q, K, A (case-insensitive), suits c/d/h/s (case-insensitive). Return the standard five-card category name in lower case; A-2-3-4-5 is a straight; royal flush is reported as "straight flush".

Why this case matters

Poker engines settle real money pots from these comparisons; a single misranked hand pays the wrong seat.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import collections
N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    vals=sorted((R.index('T' if c[:-1]=='10' else c[:-1].upper())+2 for c in x), reverse=True)
    suits=[c[-1].lower() for c in x]
    cnt=sorted(collections.Counter(vals).values(), reverse=True)
    flush=len(set(suits))==1
    uniq=sorted(set(vals))
    straight=False
    if len(uniq)==5:
        if uniq[4]-uniq[0]==4: straight=True
        elif uniq==[1,2,3,4,5]: straight=True
    if straight and flush: return 'straight flush'
    if cnt[0]==4: return 'four of a kind'
    if cnt==[3,2]: return 'full house'
    if flush: return 'flush'
    if straight: return 'straight'
    if cnt[0]==3: return 'three of a kind'
    if cnt==[2,2,1]: return 'two pair'
    if cnt[0]==2: return 'one pair'
    return 'high card'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('plain flush', ['2h', '7h', '9h', 'Jh', 'Kh'], 'flush'),
  ('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah'], 'straight'),
  ('trips', ['7h', '7d', '7c', 'Ks', '2h'], 'three of a kind'),
  ('full house', ['7h', '7d', '7c', 'Ks', 'Kh'], 'full house')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('full house', ['7h', '7d', '7c', 'Ks', 'Kh'], 'full house'),
  ('one pair', ['9h', '9d', '4c', 'Ks', '2h'], 'one pair'),
  ('two pair', ['9h', '9d', '4c', '4s', '2h'], 'two pair'),
  ('ten written as 10', ['10h', 'Jd', 'Qc', 'Ks', '9h'], 'straight')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('ten written as 10', ['10h', 'Jd', 'Qc', 'Ks', '9h'], 'straight'),
  ('lower-case ranks', ['kd', 'kh', '3c', '3s', '8h'], 'two pair'),
  ('mixed-case suits flush', ['2H', '7h', '9h', 'JH', 'Kh'], 'flush'),
  ('four-flush only', ['2h', '7h', '9h', 'Jh', 'Ks'], 'high card')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('four-flush only', ['2h', '7h', '9h', 'Jh', 'Ks'], 'high card'),
  ('quads', ['6h', '6d', '6c', '6s', '2h'], 'four of a kind'),
  ('high card', ['2h', '7d', '9c', 'Js', 'Kh'], 'high card'),
  ('straight flush middle', ['5d', '6d', '7d', '8d', '9d'], 'straight flush')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('plain flush', ['2h', '7h', '9h', 'Jh', 'Kh'], 'flush'),
  ('straight flush middle', ['5d', '6d', '7d', '8d', '9d'], 'straight flush'),
  ('ten flush with 10 token', ['10c', '2c', '5c', '8c', 'Qc'], 'flush'),
  ('flush ends match only', ['2h', '7d', '9h', 'Jc', 'Kh'], 'high card')]]
for label, args, expected in fixtures[N-1]:
    try:
        actual = solve(args)
    except Exception as exc:
        actual = 'error:' + type(exc).__name__
    check(label, actual, 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
wheel straight	`high card`	`straight`	Failed
wheel straight flush	`flush`	`straight flush`	Failed
four to wheel plus nine	`high card`	`high card`	Passed
four to wheel plus king	`high card`	`high card`	Passed
plain flush	`flush`	`flush`	Passed
broadway	`straight`	`straight`	Passed
trips	`three of a kind`	`three of a kind`	Passed
full house	`full house`	`full house`	Passed

SHA-256 / 2c212a65693de779e573254cf30ac9e3e0ae3a57d25b247542d5df6fdc291362

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import collections
N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    vals=sorted((R.index('T' if c[:-1]=='10' else c[:-1].upper())+2 for c in x), reverse=True)
    suits=[c[-1].lower() for c in x]
    cnt=sorted(collections.Counter(vals).values(), reverse=True)
    flush=len(set(suits))==1
    uniq=sorted(set(vals))
    straight=False
    if len(uniq)==5:
        if uniq[4]-uniq[0]==4: straight=True
        elif uniq[:4]==[2,3,4,5]: straight=True
    if straight and flush: return 'straight flush'
    if cnt[0]==4: return 'four of a kind'
    if cnt==[3,2]: return 'full house'
    if flush: return 'flush'
    if straight: return 'straight'
    if cnt[0]==3: return 'three of a kind'
    if cnt==[2,2,1]: return 'two pair'
    if cnt[0]==2: return 'one pair'
    return 'high card'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('plain flush', ['2h', '7h', '9h', 'Jh', 'Kh'], 'flush'),
  ('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah'], 'straight'),
  ('trips', ['7h', '7d', '7c', 'Ks', '2h'], 'three of a kind'),
  ('full house', ['7h', '7d', '7c', 'Ks', 'Kh'], 'full house')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('full house', ['7h', '7d', '7c', 'Ks', 'Kh'], 'full house'),
  ('one pair', ['9h', '9d', '4c', 'Ks', '2h'], 'one pair'),
  ('two pair', ['9h', '9d', '4c', '4s', '2h'], 'two pair'),
  ('ten written as 10', ['10h', 'Jd', 'Qc', 'Ks', '9h'], 'straight')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('ten written as 10', ['10h', 'Jd', 'Qc', 'Ks', '9h'], 'straight'),
  ('lower-case ranks', ['kd', 'kh', '3c', '3s', '8h'], 'two pair'),
  ('mixed-case suits flush', ['2H', '7h', '9h', 'JH', 'Kh'], 'flush'),
  ('four-flush only', ['2h', '7h', '9h', 'Jh', 'Ks'], 'high card')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('four-flush only', ['2h', '7h', '9h', 'Jh', 'Ks'], 'high card'),
  ('quads', ['6h', '6d', '6c', '6s', '2h'], 'four of a kind'),
  ('high card', ['2h', '7d', '9c', 'Js', 'Kh'], 'high card'),
  ('straight flush middle', ['5d', '6d', '7d', '8d', '9d'], 'straight flush')],
 [('wheel straight', ['Ah', '2d', '3c', '4s', '5h'], 'straight'),
  ('wheel straight flush', ['As', '2s', '3s', '4s', '5s'], 'straight flush'),
  ('four to wheel plus nine', ['2h', '3d', '4c', '5s', '9h'], 'high card'),
  ('four to wheel plus king', ['2h', '3d', '4c', '5s', 'Kh'], 'high card'),
  ('plain flush', ['2h', '7h', '9h', 'Jh', 'Kh'], 'flush'),
  ('straight flush middle', ['5d', '6d', '7d', '8d', '9d'], 'straight flush'),
  ('ten flush with 10 token', ['10c', '2c', '5c', '8c', 'Qc'], 'flush'),
  ('flush ends match only', ['2h', '7d', '9h', 'Jc', 'Kh'], 'high card')]]
for label, args, expected in fixtures[N-1]:
    try:
        actual = solve(args)
    except Exception as exc:
        actual = 'error:' + type(exc).__name__
    check(label, actual, 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
wheel straight	`straight`	`straight`	Passed
wheel straight flush	`straight flush`	`straight flush`	Passed
four to wheel plus nine	`straight`	`high card`	Failed
four to wheel plus king	`straight`	`high card`	Failed
plain flush	`flush`	`flush`	Passed
broadway	`straight`	`straight`	Passed
trips	`three of a kind`	`three of a kind`	Passed
full house	`full house`	`full house`	Passed

SHA-256 / fbcbaeef73782919a2af5f8be2e8044b41ad0377755af410ba241ae009612634

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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

A deterministic toy model with an explicitly stated contract; card strings are rank+suit (for example "As", "Td", "10h"); no claim of conformance to any casino or tournament rulebook. 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 2026-09-29T14:50:06.647813+00:00.

Case digest / 8652737b1de207526e085dd1c5ae577a2c58c087d83f1a2074651470192b75e7