{"abstract":"A subtraction chain builds a right-associated tree.","category":"Parsing","checks":4,"contract":"Parse a valid alternating operand/minus token list with left associativity.","contract_signature":"x","evaluation_group":"model-9f0f331789f8d851","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-infix-subtraction-associativity","id":"FA-4056","implementations":{"attempt":{"sha256":"70ed0e0f6d80ec602c4d32b7bc480f501f9b0f878d74a9016821ccf3699415e0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        return ['-',x[0],x[-1]] if len(x)>1 else x[0]\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve(['a', '-', 'b', '-', 'c']), ['-', ['-', 'a', 'b'], 'c'])\ncheck('boundary 2', solve(['x']), 'x')\ncheck('boundary 3', solve(['a', '-', 'b']), ['-', 'a', 'b'])\ncheck('boundary 4', solve(['a', '-', 'b', '-', 'c', '-', 'd']), ['-', ['-', ['-', 'a', 'b'], 'c'], 'd'])\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":"84829e7f67a1c8abdb24cae12f44c24ff62865ab9cafdbd0480d36cbfada5827","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        tree=x[-1]\n        for i in range(len(x)-2,0,-2): tree=[x[i],x[i-1],tree]\n        return tree\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve(['a', '-', 'b', '-', 'c']), ['-', ['-', 'a', 'b'], 'c'])\ncheck('boundary 2', solve(['x']), 'x')\ncheck('boundary 3', solve(['a', '-', 'b']), ['-', 'a', 'b'])\ncheck('boundary 4', solve(['a', '-', 'b', '-', 'c', '-', 'd']), ['-', ['-', ['-', 'a', 'b'], 'c'], 'd'])\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":"xp-infix-subtraction-associativity","generated_at":"2026-09-29T14:37:34.961370+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Parse a valid alternating operand/minus token list with left associativity.","sha256":"af26ff5fef39152fecbaea6e7547a2fb3e29264e8ec96a818cacfd133ce831fb","title":"A subtraction chain builds a right-associated tree · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":58.661,"exit_code":1,"observations":[{"actual":["-","a","c"],"check":"boundary 1","expected":["-",["-","a","b"],"c"],"passed":false},{"actual":"x","check":"boundary 2","expected":"x","passed":true},{"actual":["-","a","b"],"check":"boundary 3","expected":["-","a","b"],"passed":true},{"actual":["-","a","d"],"check":"boundary 4","expected":["-",["-",["-","a","b"],"c"],"d"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [\"-\", \"a\", \"c\"], \"expected\": [\"-\", [\"-\", \"a\", \"b\"], \"c\"], \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"x\", \"expected\": \"x\", \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [\"-\", \"a\", \"b\"], \"expected\": [\"-\", \"a\", \"b\"], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [\"-\", \"a\", \"d\"], \"expected\": [\"-\", [\"-\", [\"-\", \"a\", \"b\"], \"c\"], \"d\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":55.07,"exit_code":1,"observations":[{"actual":["-","a",["-","b","c"]],"check":"boundary 1","expected":["-",["-","a","b"],"c"],"passed":false},{"actual":"x","check":"boundary 2","expected":"x","passed":true},{"actual":["-","a","b"],"check":"boundary 3","expected":["-","a","b"],"passed":true},{"actual":["-","a",["-","b",["-","c","d"]]],"check":"boundary 4","expected":["-",["-",["-","a","b"],"c"],"d"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [\"-\", \"a\", [\"-\", \"b\", \"c\"]], \"expected\": [\"-\", [\"-\", \"a\", \"b\"], \"c\"], \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": \"x\", \"expected\": \"x\", \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [\"-\", \"a\", \"b\"], \"expected\": [\"-\", \"a\", \"b\"], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [\"-\", \"a\", [\"-\", \"b\", [\"-\", \"c\", \"d\"]]], \"expected\": [\"-\", [\"-\", [\"-\", \"a\", \"b\"], \"c\"], \"d\"], \"passed\": false}], \"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."}}