FAILURE MAP
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FA-3711 / Binary formats / Open access

Run-length encoding forgets the final run · case 01

Run-length encoding forgets the final run.

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: Encode a list as count/value runs, retaining adjacent equal values in one run.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Encode a list as count/value runs, retaining adjacent equal values in one run.

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

Case contract

Encode a list as count/value runs, retaining adjacent equal values in one run.

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 [[1,v] for v in x]
    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([1, 1, 2]), [[2, 1], [1, 2]])
check('boundary 2', solve([3]), [[1, 3]])
check('boundary 3', solve([]), [])
check('boundary 4', solve([1, 2, 1]), [[1, 1], [1, 2], [1, 1]])
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
boundary 1[[1, 1], [1, 1], [1, 2]][[2, 1], [1, 2]]Failed
boundary 2[[1, 3]][[1, 3]]Passed
boundary 3[][]Passed
boundary 4[[1, 1], [1, 2], [1, 1]][[1, 1], [1, 2], [1, 1]]Passed

SHA-256 / 8e61752c025de1142054132ce40564551c81d065f4d803ada0760090d760e316

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:
        out=[]
        for v in x:
            if out and out[-1][1]==v: out[-1][0]+=1
            else: out.append([1,v])
        return out[:-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([1, 1, 2]), [[2, 1], [1, 2]])
check('boundary 2', solve([3]), [[1, 3]])
check('boundary 3', solve([]), [])
check('boundary 4', solve([1, 2, 1]), [[1, 1], [1, 2], [1, 1]])
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
boundary 1[[2, 1]][[2, 1], [1, 2]]Failed
boundary 2[][[1, 3]]Failed
boundary 3[][]Passed
boundary 4[[1, 1], [1, 2]][[1, 1], [1, 2], [1, 1]]Failed

SHA-256 / f45523c4e18e2b324c57baa88e291a1db818b894a5946b1e2ca8c0204875fb42

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:
        out=[]
        for v in x:
            if out and out[-1][1]==v: out[-1][0]+=1
            else: out.append([1,v])
        return out
    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([1, 1, 2]), [[2, 1], [1, 2]])
check('boundary 2', solve([3]), [[1, 3]])
check('boundary 3', solve([]), [])
check('boundary 4', solve([1, 2, 1]), [[1, 1], [1, 2], [1, 1]])
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
boundary 1[[2, 1], [1, 2]][[2, 1], [1, 2]]Passed
boundary 2[[1, 3]][[1, 3]]Passed
boundary 3[][]Passed
boundary 4[[1, 1], [1, 2], [1, 1]][[1, 1], [1, 2], [1, 1]]Passed

SHA-256 / e95f6e3ff36f21eb0ebca5ac2e1eec888b61d140f8b080661c826eb0a9a89e28

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 2026-09-29T14:37:29.842865+00:00.

Case digest / ad8e29538c55a0d36157140fb37fe679822fb9e909984dc8514a73bbc3518277