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Diffstat (limited to 'Doc/reference/grammar.rst')
| -rw-r--r-- | Doc/reference/grammar.rst | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/Doc/reference/grammar.rst b/Doc/reference/grammar.rst index b9cca4444c9..55c148801d8 100644 --- a/Doc/reference/grammar.rst +++ b/Doc/reference/grammar.rst @@ -8,15 +8,15 @@ used to generate the CPython parser (see :source:`Grammar/python.gram`). The version here omits details related to code generation and error recovery. -The notation is a mixture of `EBNF -<https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form>`_ -and `PEG <https://en.wikipedia.org/wiki/Parsing_expression_grammar>`_. -In particular, ``&`` followed by a symbol, token or parenthesized -group indicates a positive lookahead (i.e., is required to match but -not consumed), while ``!`` indicates a negative lookahead (i.e., is -required *not* to match). We use the ``|`` separator to mean PEG's -"ordered choice" (written as ``/`` in traditional PEG grammars). See -:pep:`617` for more details on the grammar's syntax. +The notation used here is the same as in the preceding docs, +and is described in the :ref:`notation <notation>` section, +except for a few extra complications: + +* ``&e``: a positive lookahead (that is, ``e`` is required to match but + not consumed) +* ``!e``: a negative lookahead (that is, ``e`` is required *not* to match) +* ``~`` ("cut"): commit to the current alternative and fail the rule + even if this fails to parse .. literalinclude:: ../../Grammar/python.gram :language: peg |