I've recently written a short Informational PEP describing all the
places that may need updating when you change Python's Grammar.
Naturally, it's on the web at
http://www.python.org/peps/pep-0306.html
I'd be very grateful if people could scan through it and tell me about
or just add anything I've missed, particularly the Jython issues.
PEP: 306
Title: How to Change Python's Grammar
Version: $Revision: 1.2 $
Last-Modified: $Date: 2003/01/30 10:27:45 $
Author: Michael Hudson
Status: Draft
Type: Informational
Content-Type: text/plain
Created: 29-Jan-2003
Post-History:
Abstract
There's more to changing Python's grammar than editing
Grammar/Grammar and Python/compile.c. This PEP aims to be a
checklist of places that must also be fixed.
It is probably incomplete. If you see omissions, just add them if
you can -- you are not going to offend the author's sense of
ownership. Otherwise submit a bug or patch and assign it to mwh.
This PEP is not intended to be an instruction manual on Python
grammar hacking, for several reasons.
Rationale
People are getting this wrong all the time; it took well over a
year before someone noticed[1] that adding the floor division
operator (//) broke the parser module.
Checklist
__ Grammar/Grammar: OK, you'd probably worked this one out :)
__ Python/compile.c: you'll most likely need to edit both the
actual compiler and the symtable builder (which is to say both
the com_foo and the sym_foo functions).
__ You may need to regenerate Lib/symbol.py and/or Lib/token.py.
__ The parser module. Add some of your new syntax to test_parser,
bang on parsermodule.c until it passes.
__ The compiler package. A good test is to compile the standard
library and test suite with the compiler package and then check
it runs. You did add some of your new syntax to the test
suite, didn't you? There's a script in Tools/compiler that
does this.
__ If you've gone so far as to change the token structure of
Python, then the tokenizer library module will need to be
changed.
__ Certain changes may require tweaks to the library module
pycblr.
__ Jython too will need work, but I don't know what. Explanations
gratefully received.
References
[1] SF Bug #676521, parser module validation failure
http://www.python.org/sf/676521
Copyright
This document has been placed in the public domain.
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--
I don't have any special knowledge of all this. In fact, I made all
the above up, in the hope that it corresponds to reality.
-- Mark Carroll, ucam.chat
