In addition to the changes proposed here that go beyond PEP-634 (which other people discuss), I find that many of the definitions fail to capture some of the basic features of PEP-634, especially when nesting patterns.
Take for example: "case [int(), str()]". According to https://www.python.org/dev/peps/pep-0653/#sequence-patterns that desugars to: if $kind & MATCH_SEQUENCE: if $list is None: $list = list($value) if len($list) == len([int(), str()]): int(), str() = $list *# This is invalid!* if guard: DONE In general, the way these semantics are defined non-recursively over patterns won't be able to work with nested patterns. I value the idea of having a more accurate definition of what the semantics are, but this approach doesn't seem to work. Best, D. On Thu, 18 Feb 2021 at 16:45, Mark Shannon <m...@hotpy.org> wrote: > Hi everyone, > > I'd like to announce a new PEP. > https://www.python.org/dev/peps/pep-0653/ > > It builds on PEP 634 (Structural Pattern Matching: Specification), adding: > > More precise semantics. > A bit more customization for complex classes. > > Its also a bit more robust and should be faster (eventually). > > The syntax is unchanged, and in most cases the semantics are the same. > > As always, comments and suggestions are welcome. > > Cheers, > Mark. > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/O4I345VHIQUXPDJWPDA54RWVXMYEEBRM/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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