{"abstract":"The operation returns a result or retained state that violates this contract: Delete all original positions selected by a positive stride in one operation.","category":"Container mutation","checks":4,"contract":"Delete all original positions selected by a positive stride in one operation. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","contract_signature":"x, y=None","evaluation_group":"model-1baa8d8e7ee57bc1","failed_approach":"Selecting only offset-one stride positions loses other surviving positions for larger strides.","family":"xr-slice-deletion-does-not-shift-followup-indices","id":"FA-4361","implementations":{"attempt":{"sha256":"0bc69a2d132e0cbdc258378207a86e3a0402546b816ce695320b2b880ea5ca2b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return x[1::y]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('positions shift after pop', solve(['a', 'b', 'c', 'd', 'e'], 2), ['b', 'd'])\ncheck('remove all', solve(['a', 'b'], 1), [])\ncheck('empty', solve([], 2), [])\ncheck('large step', solve(['a', 'b', 'c'], 8), ['b', 'c'])\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":"398662963b757ac2c298492904369cb0f467dd80d6a902f956479db1edb1bbb5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y=None):\n    a=list(x)\n    for i in range(0,len(x),y):\n        if i<len(a): a.pop(i)\n    return a\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('positions shift after pop', solve(['a', 'b', 'c', 'd', 'e'], 2), ['b', 'd'])\ncheck('remove all', solve(['a', 'b'], 1), [])\ncheck('empty', solve([], 2), [])\ncheck('large step', solve(['a', 'b', 'c'], 8), ['b', 'c'])\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-slice-deletion-does-not-shift-followup-indices","generated_at":"2026-09-29T14:37:38.429339+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.","root_cause":"Repeated forward pops change the meaning of later original indices.","sha256":"7740d8e11c8b5e52326c7cb79f1a241f94f15fb7f82f347005c1ad6cb7f8eafc","title":"Slice deletion does not shift followup indices · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":36.227,"exit_code":1,"observations":[{"actual":["b","d"],"check":"positions shift after pop","expected":["b","d"],"passed":true},{"actual":["b"],"check":"remove all","expected":[],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":["b"],"check":"large step","expected":["b","c"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"positions shift after pop\", \"actual\": [\"b\", \"d\"], \"expected\": [\"b\", \"d\"], \"passed\": true}, {\"check\": \"remove all\", \"actual\": [\"b\"], \"expected\": [], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"large step\", \"actual\": [\"b\"], \"expected\": [\"b\", \"c\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.639,"exit_code":1,"observations":[{"actual":["b","c","e"],"check":"positions shift after pop","expected":["b","d"],"passed":false},{"actual":["b"],"check":"remove all","expected":[],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":["b","c"],"check":"large step","expected":["b","c"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"positions shift after pop\", \"actual\": [\"b\", \"c\", \"e\"], \"expected\": [\"b\", \"d\"], \"passed\": false}, {\"check\": \"remove all\", \"actual\": [\"b\"], \"expected\": [], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"large step\", \"actual\": [\"b\", \"c\"], \"expected\": [\"b\", \"c\"], \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}