{"abstract":"The operation returns a result or retained state that violates this contract: Replace values at the selected positive stride positions; replacement length matches selected length.","category":"Container mutation","checks":4,"contract":"Replace values at the selected positive stride positions; replacement length matches selected length. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","evaluation_group":"model-4937606ea13fb94c","failed_approach":"Beginning the stride at position one shifts every replacement target.","family":"xr-extended-slice-assignment-stride","id":"FA-4356","implementations":{"attempt":{"sha256":"bdd3c1387d0f186d306870098b767578ed7a19b288ddf28472c88691b9ab19ed","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    a=list(x); a[1::y[0]]=y[1][:len(a[1::y[0]])]; return a\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('alternating positions', solve(['a', 'b', 'c', 'd'], [2, ['x', 'y']]), ['x', 'b', 'y', 'd'])\ncheck('stride one', solve(['a', 'b'], [1, ['x', 'y']]), ['x', 'y'])\ncheck('empty selection', solve([], [2, []]), [])\ncheck('large stride', solve(['a', 'b'], [8, ['x']]), ['x', 'b'])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"b4457f1f55abb66736627adb6110ff7351dcfa6f6c76a76546242c5c372b2483","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    a=list(x); a[:len(y[1])]=y[1]; return a\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('alternating positions', solve(['a', 'b', 'c', 'd'], [2, ['x', 'y']]), ['x', 'b', 'y', 'd'])\ncheck('stride one', solve(['a', 'b'], [1, ['x', 'y']]), ['x', 'y'])\ncheck('empty selection', solve([], [2, []]), [])\ncheck('large stride', solve(['a', 'b'], [8, ['x']]), ['x', 'b'])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"d1b4ceb33f98c9d8dfcca3ee5bdba7a983318550a96eae4298e607205fb4b88c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    a=list(x); a[::y[0]]=y[1]; return a\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('alternating positions', solve(['a', 'b', 'c', 'd'], [2, ['x', 'y']]), ['x', 'b', 'y', 'd'])\ncheck('stride one', solve(['a', 'b'], [1, ['x', 'y']]), ['x', 'y'])\ncheck('empty selection', solve([], [2, []]), [])\ncheck('large stride', solve(['a', 'b'], [8, ['x']]), ['x', 'b'])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" 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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xr-extended-slice-assignment-stride","generated_at":"2026-09-29T14:37:38.349479+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.","repair":"Replace values at the selected positive stride positions; replacement length matches selected length.","root_cause":"A contiguous assignment overwrites intervening positions outside the stride.","sha256":"a871eae9ad7fb235cf5943ec422c0e094a40ef5c206098611780caba899a2329","title":"Extended slice assignment stride · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verification":{"attempt":{"elapsed_ms":37.682,"exit_code":1,"observations":[{"actual":["a","x","c","y"],"check":"alternating positions","expected":["x","b","y","d"],"passed":false},{"actual":["a","x"],"check":"stride one","expected":["x","y"],"passed":false},{"actual":[],"check":"empty selection","expected":[],"passed":true},{"actual":["a","x"],"check":"large stride","expected":["x","b"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"alternating positions\", \"actual\": [\"a\", \"x\", \"c\", \"y\"], \"expected\": [\"x\", \"b\", \"y\", \"d\"], \"passed\": false}, {\"check\": \"stride one\", \"actual\": [\"a\", \"x\"], \"expected\": [\"x\", \"y\"], \"passed\": false}, {\"check\": \"empty selection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"large stride\", \"actual\": [\"a\", \"x\"], \"expected\": [\"x\", \"b\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.613,"exit_code":1,"observations":[{"actual":["x","y","c","d"],"check":"alternating positions","expected":["x","b","y","d"],"passed":false},{"actual":["x","y"],"check":"stride one","expected":["x","y"],"passed":true},{"actual":[],"check":"empty selection","expected":[],"passed":true},{"actual":["x","b"],"check":"large stride","expected":["x","b"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"alternating positions\", \"actual\": [\"x\", \"y\", \"c\", \"d\"], \"expected\": [\"x\", \"b\", \"y\", \"d\"], \"passed\": false}, {\"check\": \"stride one\", \"actual\": [\"x\", \"y\"], \"expected\": [\"x\", \"y\"], \"passed\": true}, {\"check\": \"empty selection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"large stride\", \"actual\": [\"x\", \"b\"], \"expected\": [\"x\", \"b\"], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":39.575,"exit_code":0,"observations":[{"actual":["x","b","y","d"],"check":"alternating positions","expected":["x","b","y","d"],"passed":true},{"actual":["x","y"],"check":"stride one","expected":["x","y"],"passed":true},{"actual":[],"check":"empty selection","expected":[],"passed":true},{"actual":["x","b"],"check":"large stride","expected":["x","b"],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"alternating positions\", \"actual\": [\"x\", \"b\", \"y\", \"d\"], \"expected\": [\"x\", \"b\", \"y\", \"d\"], \"passed\": true}, {\"check\": \"stride one\", \"actual\": [\"x\", \"y\"], \"expected\": [\"x\", \"y\"], \"passed\": true}, {\"check\": \"empty selection\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"large stride\", \"actual\": [\"x\", \"b\"], \"expected\": [\"x\", \"b\"], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}