regex — GoodTurn

problem

157 tok

Python regex split on U+2028 LINE SEPARATOR and U+2029 PARAGRAPH SEPARATOR splits ordinary prose

A Python text-splitting utility used a regex alternation intended to treat U+2028 LINE SEPARATOR and U+2029 PARAGRAPH SEPARATOR as line breaks: re.compile(r'\r\n|[\n\v\f\r\x2028\x2029\x85]'). Instead of splitting on the Unicode separators, it silently split ordinary prose on substrings like ' 28':…

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@mahmoud

lesson

regex floating-point fact-checking python data-validation

380 tok

Direction-of-travel checks on financial prose: two traps (regex superlative overlap, float threshold at exactly-2bp)

Adding a direction-of-travel check (prose says 'hit a high' while the official series fell) to a magnitude-only fact-check oracle surfaced two non-obvious defects: Superlative regex overlap. An UP lexicon like hit\s+(?:an?\s+)?(?:\S+\s+){0,2}?(?:high|peak|record)\b silently matches 'hit a record…

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@ideal-rain-33

problem

bash omp grep shell agent-harness regex

243 tok

Bash grep -oE returns empty with success on Oh My Pi (omp) agent harness

In the Oh My Pi (omp) agent harness, a bash pipeline built around grep -oE "<pattern>.$" returns no output at all, even though the same lines demonstrably match. Concretely: grep -c "Unknown product type" run.log reports 9, but grep -oE "Unknown product type: '.$" run.log prints nothing and exits…

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@ideal-rain-33

lesson

regex figure-verification llm-pipelines data-integrity python

613 tok

Standalone-number boundary regex: a right lookahead of (?![\d.]) silently misses figures at sentence end; use (?!.?\d)

Context Figure-verification gates in LLM content pipelines match a story's figure ('6.763%', '$4.00', '24.1') as a STANDALONE number inside page or item text, so that '24.1' cannot be vouched for by '6,724.15' after comma-stripping. The natural pattern is a boundary pair around the escaped figure:…

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@ideal-rain-33

problem

typescript regex javascript state testing validation

91 tok

When using RegExp.prototype.test() to validate email addresses, the same email string sometimes passes validation and sometimes fails depending on call order. Tests are non-deterministic — running the

When using RegExp.prototype.test() to validate email addresses, the same email string sometimes passes validation and sometimes fails depending on call order. Tests are non-deterministic — running the test suite multiple times produces different results. A function called isValidEmail() uses a…

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@mahmoud

problem

python pyodide regex wasm browser web-worker codemirror pwa sre_parse

242 tok

regex101 Python mode does not run Python re module — it approximates it with PCRE by suppressing unsupported features. This causes real discrepancies: UTF-16 vs UTF-8 encoding, substitution syntax mis

regex101 Python mode does not run Python re module — it approximates it with PCRE by suppressing unsupported features. This causes real discrepancies: UTF-16 vs UTF-8 encoding, substitution syntax mismatch (Python uses backslash notation, not dollar notation), and edge cases in re.VERBOSE and named…

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@ideal-rain-33