FA-3726 / Binary formats / Open access

Delta decoding omits the first absolute sample · case 01

Delta decoding omits the first absolute sample.

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 first item as absolute and later items as signed deltas.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Decode first item as absolute and later items as signed deltas.

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

Case contract

Decode first item as absolute and later items as signed deltas.

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 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([10, 2, -3]), [10, 12, 9])
check('boundary 2', solve([5]), [5])
check('boundary 3', solve([]), [])
check('boundary 4', solve([0, 0, 1]), [0, 0, 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 fixture	Actual	Expected	Outcome
boundary 1	`[10, 2, -3]`	`[10, 12, 9]`	Failed
boundary 2	`[5]`	`[5]`	Passed
boundary 3	`[]`	`[]`	Passed
boundary 4	`[0, 0, 1]`	`[0, 0, 1]`	Passed

SHA-256 / 415f968e0e863f13e6dee77ae660a5e6c6a5b9f4b3a52363201d0b04ee5863f2

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 [sum(x[1:i+1]) for i in range(len(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([10, 2, -3]), [10, 12, 9])
check('boundary 2', solve([5]), [5])
check('boundary 3', solve([]), [])
check('boundary 4', solve([0, 0, 1]), [0, 0, 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 fixture	Actual	Expected	Outcome
boundary 1	`[0, 2, -1]`	`[10, 12, 9]`	Failed
boundary 2	`[0]`	`[5]`	Failed
boundary 3	`[]`	`[]`	Passed
boundary 4	`[0, 0, 1]`	`[0, 0, 1]`	Passed

SHA-256 / 6d25b1e2e22b699c10e2cf4f85afb4316c962125f8f6137747d87f99cecae378

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 [sum(x[:i+1]) for i in range(len(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([10, 2, -3]), [10, 12, 9])
check('boundary 2', solve([5]), [5])
check('boundary 3', solve([]), [])
check('boundary 4', solve([0, 0, 1]), [0, 0, 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 fixture	Actual	Expected	Outcome
boundary 1	`[10, 12, 9]`	`[10, 12, 9]`	Passed
boundary 2	`[5]`	`[5]`	Passed
boundary 3	`[]`	`[]`	Passed
boundary 4	`[0, 0, 1]`	`[0, 0, 1]`	Passed

SHA-256 / 9d7d523f2e9aeb3cc42db83aa0652a9187001399fe5f17692840d41a3f1c17e3

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 2026-09-29T14:37:30.062804+00:00.

Case digest / 3d66967e8b0e9c3d59cc398df880ea785dc278546d5afd830a50d0ab077e6cb1