gh-152100: Support set operations in character classes#152153
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Implement set difference [A--B], intersection [A&&B] and union [A||B] in regular expression character classes (Unicode Technical Standard #18), including nested, complemented and compound set operands. Symmetric difference [A~~B] remains reserved. Also use the new syntax in the standard library (_strptime, textwrap, doctest, pkgutil). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Implement UTS #18 RL1.3 set operations in regular expression character classes: difference
[A--B], intersection[A&&B]and union[A||B], with nested, complemented and compound operands and arbitrary left-to-right chaining ([a-z--[aeiou]&&\w]). Symmetric difference[A~~B]remains reserved (still aFutureWarning).These tokens (
--,&&,||, and nested[) have been reserved since 3.7 viaFutureWarning, so this turns the warnings into real syntax.The feature is parser-only: each operation maps to an assertion on the matched character —
[A--B]→A(?<![B]),[A&&B]→A(?<=[B]),[A||B]→ a merged charset[AB]or an alternation — so no charset complement is ever formed and the result is correct underIGNORECASE. A leading^negates by De Morgan, pushing the negation into the operands. The engine andMAGICare untouched.A
[opens a nested set only immediately after a set operator; at the start of a class it stays an ordinary literal, so existing patterns such as[[:alpha:]]and glob's[*?[]keep their meaning.The new syntax is also used in the standard library (
_strptime,textwrap,doctest,pkgutil).🤖 Generated with Claude Code