116 lines
3.2 KiB
Plaintext
116 lines
3.2 KiB
Plaintext
PEP: 306
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Title: How to Change Python's Grammar
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Version: $Revision$
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Last-Modified: $Date$
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Author: Michael Hudson <mwh@python.net>, Jack Diederich <jackdied@gmail.com>, Nick Coghlan <ncoghlan@gmail.com>, Benjamin Peterson <benjamin@python.org>
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Status: Withdrawn
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Type: Informational
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Content-Type: text/x-rst
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Created: 29-Jan-2003
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Post-History: 30-Jan-2003
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Note
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====
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This PEP has been moved to the Python dev guide [1]_.
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Abstract
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========
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There's more to changing Python's grammar than editing
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Grammar/Grammar and Python/compile.c. This PEP aims to be a
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checklist of places that must also be fixed.
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It is probably incomplete. If you see omissions, just add them if
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you can -- you are not going to offend the author's sense of
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ownership. Otherwise submit a bug or patch and assign it to mwh.
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This PEP is not intended to be an instruction manual on Python
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grammar hacking, for several reasons.
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Rationale
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=========
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People are getting this wrong all the time; it took well over a
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year before someone noticed [2]_ that adding the floor division
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operator (//) broke the parser module.
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Checklist
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=========
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- Grammar/Grammar: OK, you'd probably worked this one out :)
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- Parser/Python.asdl may need changes to match the Grammar. Run
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make to regenerate Include/Python-ast.h and
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Python/Python-ast.c.
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- Python/ast.c will need changes to create the AST objects
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involved with the Grammar change. Lib/compiler/ast.py will
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need matching changes to the pure-python AST objects.
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- Parser/pgen needs to be rerun to regenerate Include/graminit.h
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and Python/graminit.c. (make should handle this for you.)
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- Python/symbtable.c: This handles the symbol collection pass
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that happens immediately before the compilation pass.
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- Python/compile.c: You will need to create or modify the
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``compiler_*`` functions to generate opcodes for your productions.
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- You may need to regenerate Lib/symbol.py and/or Lib/token.py
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and/or Lib/keyword.py.
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- The parser module. Add some of your new syntax to test_parser,
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bang on Modules/parsermodule.c until it passes.
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- Add some usage of your new syntax to test_grammar.py
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- The compiler package. A good test is to compile the standard
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library and test suite with the compiler package and then check
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it runs. Note that this only needs to be done in Python 2.x.
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- If you've gone so far as to change the token structure of
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Python, then the Lib/tokenizer.py library module will need to
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be changed.
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- Certain changes may require tweaks to the library module
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``pyclbr``.
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- Documentation must be written!
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- After everything's been checked in, you're likely to see a new
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change to Python/Python-ast.c. This is because this
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(generated) file contains the SVN version of the source from
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which it was generated. There's no way to avoid this; you just
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have to submit this file separately.
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References
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==========
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.. [1] CPython Developer's Guide: Changing CPython's Grammar
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http://cpython-devguide.readthedocs.io/en/latest/grammar.html
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.. [2] SF Bug #676521, parser module validation failure
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http://www.python.org/sf/676521
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Copyright
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=========
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This document has been placed in the public domain.
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..
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Local Variables:
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fill-column: 70
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End:
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