FA-4691 / Multiset accounting / Open access
Counter unary minus selects negative side · case 01
The operation returns a result or retained state that violates this contract: Unary minus returns positive magnitudes of negative counts only.
ROOT CAUSE
Negating every count creates negative output from originally positive entries.
VERIFIED REPAIR
Unary minus returns positive magnitudes of negative counts only.
Unsuccessful approach: Absolute values incorrectly include originally positive entries.
Case contract
Unary minus returns positive magnitudes of negative counts only. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.
Why this case matters
A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
from collections import Counter, ChainMap, deque
import heapq
N = 1
observations = []
def solve(x, y=None):
return {k:-v for k,v in x.items()}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('mixed signs', solve({'a': 2, 'b': 0, 'c': -1}), {'c': 1})
check('positive omitted', solve({'a': 2}), {})
check('negative becomes positive', solve({'a': -2}), {'a': 2})
check('empty', solve({}), {})
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 |
|---|---|---|---|
| mixed signs | {'a': -2, 'b': 0, 'c': 1} | {'c': 1} | Failed |
| positive omitted | {'a': -2} | {} | Failed |
| negative becomes positive | {'a': 2} | {'a': 2} | Passed |
| empty | {} | {} | Passed |
SHA-256 / ac2470fa58dd03da401e45e491ebc81c6f4bfa74c22e8da9856505092ad73cbe
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
from collections import Counter, ChainMap, deque
import heapq
N = 1
observations = []
def solve(x, y=None):
return {k:abs(v) for k,v in x.items() if v!=0}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('mixed signs', solve({'a': 2, 'b': 0, 'c': -1}), {'c': 1})
check('positive omitted', solve({'a': 2}), {})
check('negative becomes positive', solve({'a': -2}), {'a': 2})
check('empty', solve({}), {})
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 |
|---|---|---|---|
| mixed signs | {'a': 2, 'c': 1} | {'c': 1} | Failed |
| positive omitted | {'a': 2} | {} | Failed |
| negative becomes positive | {'a': 2} | {'a': 2} | Passed |
| empty | {} | {} | Passed |
SHA-256 / 2e6afeaf7abb5c5bc1fa93a3277d1c89d1fa4ac3c2938bfa8d58c432da8c7592
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
from collections import Counter, ChainMap, deque
import heapq
N = 1
observations = []
def solve(x, y=None):
return dict(-Counter(x))
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('mixed signs', solve({'a': 2, 'b': 0, 'c': -1}), {'c': 1})
check('positive omitted', solve({'a': 2}), {})
check('negative becomes positive', solve({'a': -2}), {'a': 2})
check('empty', solve({}), {})
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 |
|---|---|---|---|
| mixed signs | {'c': 1} | {'c': 1} | Passed |
| positive omitted | {} | {} | Passed |
| negative becomes positive | {'a': 2} | {'a': 2} | Passed |
| empty | {} | {} | Passed |
SHA-256 / 31af9645fc76d8d8c3fac904290ae9b1db5f87ac6af703455ca2a6c36e6ca72c
Verification & scope
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 2026-09-29T14:37:41.826752+00:00.
Case digest / ef5b956664ff88d2b55d60f061eb34875d9a9d8d37062ec335a6a2e6afc9efa9