I wonder if David may be struggling with the rule that a newline is significant in the grammar unless it appears inside matching brackets/parentheses/braces? I think that's in the lexer. Similarly, multiple newlines are collapsed.
On Wed, Oct 26, 2022 at 1:19 PM Pablo Galindo Salgado <pablog...@gmail.com> wrote: > Hi, > > As I mentioned, NEWLINE is a token. All uppercase words in the grammar are > tokens and therefore are produced by the lexer, not the parser. Is not a > built-in rule. In particular, that token is produced here: > > > https://github.com/python/cpython/blob/6777e09166fc384ea0a4b50202c7b0bd7a23330c/Parser/tokenizer.c#L1773 > > > On Wed, 26 Oct 2022 at 20:59, David J W <ward.dav...@gmail.com> wrote: > >> Pablo, >> Nl and Newline are tokens but I am interested in NEWLINE's behavior >> in the Python grammar, note the casing. >> >> For example in simple_stmts @ >> https://github.com/python/cpython/blob/main/Grammar/python.gram#L107 >> >> Is that NEWLINE some sort of built in rule to the grammar? In my >> project I am running into problems where the parser crashes any time there >> is some double like NL & N or Newline & NL but I want to nail down >> NEWLINE's behavior in CPython's PEG grammar. >> >> On Wed, Oct 26, 2022 at 12:51 PM Pablo Galindo Salgado < >> pablog...@gmail.com> wrote: >> >>> Hi, >>> >>> I am not sure I understand exactly what you are asking but NEWLINE is a >>> token, not a parser rule. What decides when NEWLINE is emitted is the lexer >>> that has nothing to do with PEG. Normally PEG parsers also acts as >>> tokenizers but the one in cpython does not. >>> >>> Also notice that CPython’s parser uses a version of the tokeniser >>> written in C that doesn’t share code with the exposed version. You will >>> find that the tokenizer module in the standard library actually behaves >>> differently regarding what tokens are emitted in new lines and indentations. >>> >>> The only way to be sure is check the code unfortunately. >>> >>> Hope this helps. >>> >>> Regards from rainy London, >>> Pablo Galindo Salgado >>> >>> > On 26 Oct 2022, at 19:12, David J W <ward.dav...@gmail.com> wrote: >>> > >>> > >>> > I am writing a Rust version of Python for fun and I am at the parser >>> stage of development. >>> > >>> > I copied and modified a PEG grammar ruleset from another open source >>> project and I've already noticed some problems (ex Newline vs NL) with how >>> they transcribed things. >>> > >>> > I am suspecting that CPython's grammar NEWLINE is a builtin rule for >>> the parser that is something like `(Newline+ | NL+ ) {NOP}` but wanted to >>> sanity check if that is right before I figure out how to hack in a NEWLINE >>> rule and update my grammar ruleset. >>> > _______________________________________________ >>> > 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/NMCMEDMEBKATYKRNZLX2NDGFOB5UHQ5A/ >>> > Code of Conduct: http://python.org/psf/codeofconduct/ >>> >> _______________________________________________ > 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/5ZV7BZOYHW3DELYIB4GKRWHUNTYW3V4K/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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