FA-82101 / Poker hand evaluation / Open access

Ranks ordered alphabetically instead of by strength · case 01

Queen-ten is written "TQs" and ace-king "KAo".

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

ROOT CAUSE

The two ranks are sorted as characters, where T sorts after Q and K after A.

VERIFIED REPAIR

Sort by position in the rank table, highest first.

Unsuccessful approach: Sorting by rank strength ascending puts the lower card first.

Case contract

Input: two hole cards as strings (rank may be "10"; rank and suit case-insensitive). Return canonical hold'em notation: pairs "QQ", otherwise higher rank first with "s" for suited or "o" for offsuit (e.g. "AKs", "T9o"). Return "invalid" for duplicate cards or unknown ranks.

Why this case matters

Range tools, solvers and hand histories key statistics on this notation.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    if len(x)!=2 or x[0].upper()==x[1].upper(): return 'invalid'
    def rank(c):
        t=c[:-1].upper()
        return 'T' if t=='10' else t
    a,b=rank(x[0]),rank(x[1])
    if a not in list(R) or b not in list(R): return 'invalid'
    if a==b: return a+b
    hi,lo=sorted([a,b], reverse=True)
    return hi+lo+('s' if x[0][-1].lower()==x[1][-1].lower() else 'o')
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('pair of queens', ['Qh', 'Qs'], 'QQ'), ('duplicate card case', ['Ah', 'aH'], 'invalid'),
  ('exact duplicate', ['7c', '7c'], 'invalid'), ('empty rank', ['h', 'Kd'], 'invalid'),
  ('two-letter rank', ['KQh', '2d'], 'invalid'),
  ('pair of tens mixed tokens', ['10h', 'Td'], 'TT')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('ten nine suited with 10', ['10s', '9s'], 'T9s'), ('nine ten mixed', ['9c', '10d'], 'T9o'),
  ('queen ten', ['Tc', 'Qc'], 'QTs'), ('empty rank', ['h', 'Kd'], 'invalid'),
  ('two-letter rank', ['KQh', '2d'], 'invalid'),
  ('pair of tens mixed tokens', ['10h', 'Td'], 'TT')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('ten nine suited with 10', ['10s', '9s'], 'T9s'), ('nine ten mixed', ['9c', '10d'], 'T9o'),
  ('queen ten', ['Tc', 'Qc'], 'QTs'), ('lower case ranks', ['kd', 'js'], 'KJo'),
  ('suit case differs', ['Jh', 'TH'], 'JTs'), ('ten first suited', ['10h', 'Jh'], 'JTs')],
 [('nine ten mixed', ['9c', '10d'], 'T9o'), ('pair of queens', ['Qh', 'Qs'], 'QQ'),
  ('duplicate card case', ['Ah', 'aH'], 'invalid'), ('queen ten', ['Tc', 'Qc'], 'QTs'),
  ('lower case ranks', ['kd', 'js'], 'KJo'), ('suit case differs', ['Jh', 'TH'], 'JTs'),
  ('ten first suited', ['10h', 'Jh'], 'JTs'), ('deuce seven', ['2d', '7s'], '72o')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('pair of queens', ['Qh', 'Qs'], 'QQ'),
  ('duplicate card case', ['Ah', 'aH'], 'invalid'), ('queen ten', ['Tc', 'Qc'], 'QTs'),
  ('lower case ranks', ['kd', 'js'], 'KJo'), ('suit case differs', ['Jh', 'TH'], 'JTs'),
  ('ten first suited', ['10h', 'Jh'], 'JTs'), ('deuce seven', ['2d', '7s'], '72o')]]
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
ace king suited	`KAs`	`AKs`	Failed
king ace offsuit order	`KAo`	`AKo`	Failed
pair of queens	`QQ`	`QQ`	Passed
duplicate card case	`invalid`	`invalid`	Passed
exact duplicate	`invalid`	`invalid`	Passed
empty rank	`invalid`	`invalid`	Passed
two-letter rank	`invalid`	`invalid`	Passed
pair of tens mixed tokens	`TT`	`TT`	Passed

SHA-256 / c44d999b1ca76e3556e0dbd721712d542db69dd181837cffe96c29e1a39ff5e8

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    if len(x)!=2 or x[0].upper()==x[1].upper(): return 'invalid'
    def rank(c):
        t=c[:-1].upper()
        return 'T' if t=='10' else t
    a,b=rank(x[0]),rank(x[1])
    if a not in list(R) or b not in list(R): return 'invalid'
    if a==b: return a+b
    hi,lo=sorted([a,b], key=R.index)
    return hi+lo+('s' if x[0][-1].lower()==x[1][-1].lower() else 'o')
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('pair of queens', ['Qh', 'Qs'], 'QQ'), ('duplicate card case', ['Ah', 'aH'], 'invalid'),
  ('exact duplicate', ['7c', '7c'], 'invalid'), ('empty rank', ['h', 'Kd'], 'invalid'),
  ('two-letter rank', ['KQh', '2d'], 'invalid'),
  ('pair of tens mixed tokens', ['10h', 'Td'], 'TT')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('ten nine suited with 10', ['10s', '9s'], 'T9s'), ('nine ten mixed', ['9c', '10d'], 'T9o'),
  ('queen ten', ['Tc', 'Qc'], 'QTs'), ('empty rank', ['h', 'Kd'], 'invalid'),
  ('two-letter rank', ['KQh', '2d'], 'invalid'),
  ('pair of tens mixed tokens', ['10h', 'Td'], 'TT')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('ten nine suited with 10', ['10s', '9s'], 'T9s'), ('nine ten mixed', ['9c', '10d'], 'T9o'),
  ('queen ten', ['Tc', 'Qc'], 'QTs'), ('lower case ranks', ['kd', 'js'], 'KJo'),
  ('suit case differs', ['Jh', 'TH'], 'JTs'), ('ten first suited', ['10h', 'Jh'], 'JTs')],
 [('nine ten mixed', ['9c', '10d'], 'T9o'), ('pair of queens', ['Qh', 'Qs'], 'QQ'),
  ('duplicate card case', ['Ah', 'aH'], 'invalid'), ('queen ten', ['Tc', 'Qc'], 'QTs'),
  ('lower case ranks', ['kd', 'js'], 'KJo'), ('suit case differs', ['Jh', 'TH'], 'JTs'),
  ('ten first suited', ['10h', 'Jh'], 'JTs'), ('deuce seven', ['2d', '7s'], '72o')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('pair of queens', ['Qh', 'Qs'], 'QQ'),
  ('duplicate card case', ['Ah', 'aH'], 'invalid'), ('queen ten', ['Tc', 'Qc'], 'QTs'),
  ('lower case ranks', ['kd', 'js'], 'KJo'), ('suit case differs', ['Jh', 'TH'], 'JTs'),
  ('ten first suited', ['10h', 'Jh'], 'JTs'), ('deuce seven', ['2d', '7s'], '72o')]]
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
ace king suited	`KAs`	`AKs`	Failed
king ace offsuit order	`KAo`	`AKo`	Failed
pair of queens	`QQ`	`QQ`	Passed
duplicate card case	`invalid`	`invalid`	Passed
exact duplicate	`invalid`	`invalid`	Passed
empty rank	`invalid`	`invalid`	Passed
two-letter rank	`invalid`	`invalid`	Passed
pair of tens mixed tokens	`TT`	`TT`	Passed

SHA-256 / 4b35c062243345fb9f2080398f8cbe2c7e2071d2ad3fa0191f20b7f7d261872d

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    if len(x)!=2 or x[0].upper()==x[1].upper(): return 'invalid'
    def rank(c):
        t=c[:-1].upper()
        return 'T' if t=='10' else t
    a,b=rank(x[0]),rank(x[1])
    if a not in list(R) or b not in list(R): return 'invalid'
    if a==b: return a+b
    hi,lo=sorted([a,b], key=R.index, reverse=True)
    return hi+lo+('s' if x[0][-1].lower()==x[1][-1].lower() else 'o')
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('pair of queens', ['Qh', 'Qs'], 'QQ'), ('duplicate card case', ['Ah', 'aH'], 'invalid'),
  ('exact duplicate', ['7c', '7c'], 'invalid'), ('empty rank', ['h', 'Kd'], 'invalid'),
  ('two-letter rank', ['KQh', '2d'], 'invalid'),
  ('pair of tens mixed tokens', ['10h', 'Td'], 'TT')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('ten nine suited with 10', ['10s', '9s'], 'T9s'), ('nine ten mixed', ['9c', '10d'], 'T9o'),
  ('queen ten', ['Tc', 'Qc'], 'QTs'), ('empty rank', ['h', 'Kd'], 'invalid'),
  ('two-letter rank', ['KQh', '2d'], 'invalid'),
  ('pair of tens mixed tokens', ['10h', 'Td'], 'TT')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('king ace offsuit order', ['Kd', 'Ah'], 'AKo'),
  ('ten nine suited with 10', ['10s', '9s'], 'T9s'), ('nine ten mixed', ['9c', '10d'], 'T9o'),
  ('queen ten', ['Tc', 'Qc'], 'QTs'), ('lower case ranks', ['kd', 'js'], 'KJo'),
  ('suit case differs', ['Jh', 'TH'], 'JTs'), ('ten first suited', ['10h', 'Jh'], 'JTs')],
 [('nine ten mixed', ['9c', '10d'], 'T9o'), ('pair of queens', ['Qh', 'Qs'], 'QQ'),
  ('duplicate card case', ['Ah', 'aH'], 'invalid'), ('queen ten', ['Tc', 'Qc'], 'QTs'),
  ('lower case ranks', ['kd', 'js'], 'KJo'), ('suit case differs', ['Jh', 'TH'], 'JTs'),
  ('ten first suited', ['10h', 'Jh'], 'JTs'), ('deuce seven', ['2d', '7s'], '72o')],
 [('ace king suited', ['Ah', 'Kh'], 'AKs'), ('pair of queens', ['Qh', 'Qs'], 'QQ'),
  ('duplicate card case', ['Ah', 'aH'], 'invalid'), ('queen ten', ['Tc', 'Qc'], 'QTs'),
  ('lower case ranks', ['kd', 'js'], 'KJo'), ('suit case differs', ['Jh', 'TH'], 'JTs'),
  ('ten first suited', ['10h', 'Jh'], 'JTs'), ('deuce seven', ['2d', '7s'], '72o')]]
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
ace king suited	`AKs`	`AKs`	Passed
king ace offsuit order	`AKo`	`AKo`	Passed
pair of queens	`QQ`	`QQ`	Passed
duplicate card case	`invalid`	`invalid`	Passed
exact duplicate	`invalid`	`invalid`	Passed
empty rank	`invalid`	`invalid`	Passed
two-letter rank	`invalid`	`invalid`	Passed
pair of tens mixed tokens	`TT`	`TT`	Passed

SHA-256 / ef7338d2f6fa5dac3aa9abe12ae20e16835f393978814eb7b85ed257c4a22e01

Verification & scope

A deterministic toy model with an explicitly stated contract; card strings are rank+suit (for example "As", "Td"); 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 2026-09-29T14:50:08.911830+00:00.

Case digest / 6678f2ba6b39d28ce30272e006c775de7516f8773bb53036c1b48d82527093fb