FA-4271 / Collection algebra / Open access

Zip stops at shorter · case 01

The operation returns a result or retained state that violates this contract: Zip corresponding positions and stop at the shorter operand.

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

ROOT CAUSE

Each left value is paired with the first right value rather than its positional counterpart.

VERIFIED REPAIR

Zip corresponding positions and stop at the shorter operand.

Unsuccessful approach: Cartesian expansion invents cross-position pairs.

Case contract

Zip corresponding positions and stop at the shorter operand. 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

N = 1
observations = []
def solve(x, y=None):
    return [[a,y[0]] for a in x] if y else []
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('both empty', solve([], []), [])
check('empty right operand', solve(['a'], []), [])
check('empty left operand', solve([], ['b']), [])
check('overlap and multiplicity', solve(['b', 'a', 'b'], ['b', 'c', 'c']), [['b', 'b'], ['a', 'c'], ['b', 'c']])
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
both empty	`[]`	`[]`	Passed
empty right operand	`[]`	`[]`	Passed
empty left operand	`[]`	`[]`	Passed
overlap and multiplicity	`[['b', 'b'], ['a', 'b'], ['b', 'b']]`	`[['b', 'b'], ['a', 'c'], ['b', 'c']]`	Failed

SHA-256 / 6c4f458efa33b2482dbb9008c8211f59dd45c90b8a35a316d7d714e4a996f15b

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x, y=None):
    return [[a,b] for a in x for b in y]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('both empty', solve([], []), [])
check('empty right operand', solve(['a'], []), [])
check('empty left operand', solve([], ['b']), [])
check('overlap and multiplicity', solve(['b', 'a', 'b'], ['b', 'c', 'c']), [['b', 'b'], ['a', 'c'], ['b', 'c']])
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
both empty	`[]`	`[]`	Passed
empty right operand	`[]`	`[]`	Passed
empty left operand	`[]`	`[]`	Passed
overlap and multiplicity	`[['b', 'b'], ['b', 'c'], ['b', 'c'], ['a', 'b'], ['a', 'c'], ['a', 'c'], ['b', 'b'], ['b', 'c'], ['b', 'c']]`	`[['b', 'b'], ['a', 'c'], ['b', 'c']]`	Failed

SHA-256 / efebb3f828a029ee74c08ab57cac93cab1d361ecf72077b3308f4eaeef016a3c

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x, y=None):
    return [[a,b] for a,b in zip(x,y)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('both empty', solve([], []), [])
check('empty right operand', solve(['a'], []), [])
check('empty left operand', solve([], ['b']), [])
check('overlap and multiplicity', solve(['b', 'a', 'b'], ['b', 'c', 'c']), [['b', 'b'], ['a', 'c'], ['b', 'c']])
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
both empty	`[]`	`[]`	Passed
empty right operand	`[]`	`[]`	Passed
empty left operand	`[]`	`[]`	Passed
overlap and multiplicity	`[['b', 'b'], ['a', 'c'], ['b', 'c']]`	`[['b', 'b'], ['a', 'c'], ['b', 'c']]`	Passed

SHA-256 / c8c570a595badfd31a30e0df666536c8234666256d17ca7baf110a94162b2599

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 2026-09-29T14:37:37.455458+00:00.

Case digest / 7f7b8080e7b8d0320b16820aa0b9dbdfc3d683e251bfac7f1cdd147dee9b77a9