FA-3706 / Binary formats / Open access

Run-length decoding treats zero count as one · case 01

Run-length decoding treats zero count as one.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The implementation applies an operation whose text or grammar semantics violate this contract: Decode count/value pairs, allow zero counts, and reject an odd-length stream.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Decode count/value pairs, allow zero counts, and reject an odd-length stream.

Unsuccessful approach: The attempted repair handles the primary example but still violates a separate boundary of the same contract.

Case contract

Decode count/value pairs, allow zero counts, and reject an odd-length stream.

Why this case matters

A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return [v for n,v in zip(x[::2],x[1::2]) for _ in range(max(n,1))]
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve([0, 65]), [])
check('boundary 2', solve([2, 65, 1]), None)
check('boundary 3', solve([2, 65, 1, 66]), [65, 65, 66])
check('boundary 4', 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
boundary 1	`[65]`	`[]`	Failed
boundary 2	`[65, 65]`	`None`	Failed
boundary 3	`[65, 65, 66]`	`[65, 65, 66]`	Passed
boundary 4	`[]`	`[]`	Passed

SHA-256 / 04f1d88fdad87e0e2d53e0fa79d4284008045f2c2c7b928912bc8f5c1e98b09f

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return [v for n,v in zip(x[::2],x[1::2]) for _ in range(n)]
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve([0, 65]), [])
check('boundary 2', solve([2, 65, 1]), None)
check('boundary 3', solve([2, 65, 1, 66]), [65, 65, 66])
check('boundary 4', 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
boundary 1	`[]`	`[]`	Passed
boundary 2	`[65, 65]`	`None`	Failed
boundary 3	`[65, 65, 66]`	`[65, 65, 66]`	Passed
boundary 4	`[]`	`[]`	Passed

SHA-256 / de98a15facb497128bd350f1c63c4585e91eeef5ed97f4e5ecb8135ec0a2f173

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return None if len(x)%2 else [v for n,v in zip(x[::2],x[1::2]) for _ in range(n)]
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve([0, 65]), [])
check('boundary 2', solve([2, 65, 1]), None)
check('boundary 3', solve([2, 65, 1, 66]), [65, 65, 66])
check('boundary 4', 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
boundary 1	`[]`	`[]`	Passed
boundary 2	`None`	`None`	Passed
boundary 3	`[65, 65, 66]`	`[65, 65, 66]`	Passed
boundary 4	`[]`	`[]`	Passed

SHA-256 / 43c60c0da257478209b151c391d2e2eeeb9b9df797d8ffc8ad328cdfb0558b42

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 2026-09-29T14:37:29.723128+00:00.

Case digest / c79e9cbe3bac7604a8e96237e7c086eb1c3f46830324a27cb86e80f6b65d6ae9