FA-3021 / Text processing / Open access

Substring frequency counts overlapping matches · case 01

Substring frequency counts overlapping matches.

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: Count nonoverlapping occurrences of aa, using Python substring count semantics.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Count nonoverlapping occurrences of aa, using Python substring count semantics.

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

Case contract

Count nonoverlapping occurrences of aa, using Python substring count semantics.

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 sum(x[i:i+2]=='aa' 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('aaa'), 1)
check('boundary 2', solve('aaaa'), 2)
check('boundary 3', solve('aabaa'), 2)
check('boundary 4', solve(''), 0)
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	`2`	`1`	Failed
boundary 2	`3`	`2`	Failed
boundary 3	`2`	`2`	Passed
boundary 4	`0`	`0`	Passed

SHA-256 / 678838e78a4dde6565a1762f0673a4dd49a69446e4837b0de86c3e33425f1e19

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 int('aa' 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('aaa'), 1)
check('boundary 2', solve('aaaa'), 2)
check('boundary 3', solve('aabaa'), 2)
check('boundary 4', solve(''), 0)
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	`1`	`1`	Passed
boundary 2	`1`	`2`	Failed
boundary 3	`1`	`2`	Failed
boundary 4	`0`	`0`	Passed

SHA-256 / 07a8e8432371e33f80c401f2c5e750bb6b33e436a997a0a4b6eb6b0fcf867048

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 x.count('aa')
    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('aaa'), 1)
check('boundary 2', solve('aaaa'), 2)
check('boundary 3', solve('aabaa'), 2)
check('boundary 4', solve(''), 0)
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	`1`	`1`	Passed
boundary 2	`2`	`2`	Passed
boundary 3	`2`	`2`	Passed
boundary 4	`0`	`0`	Passed

SHA-256 / 54b6e73cc76e51dcf40f4445a99c5968c63d5891401a990206ba7577820085bc

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 2026-09-29T14:37:20.462739+00:00.

Case digest / d197dffda25ae8da2db5c8e79f1c907dca54c90bcd630b30008c0bab396a0b8d