Thank you for the advice everyone. This seed has finally born (rotten) fruit at:
http://writeonly.wordpress.com/2010/04/01/whython-python-for-people-who-hate-whitespace/ http://bitbucket.org/gregglind/python-whython3k/ On Fri, Mar 12, 2010 at 4:13 AM, Georg Brandl <g.bra...@gmx.net> wrote: > Am 09.03.2010 14:42, schrieb Jeremy Hylton: > > On Sat, Mar 6, 2010 at 11:27 AM, Gregg Lind <gregg.l...@gmail.com> > wrote: > >> Python-devs, > >> > >> I'm writing to you for some help in understanding the Python grammar. > As an > >> excuse to deep dive into Python's tokenizer / grammar, I decided (as a > >> hideous, hideous joke) to want to allow braces where colons are allowed > (as > >> flow control). > >> > >> Starting from PEP 306 (and branch r311), I hacked on Grammar/Grammer > >> > >> As a first example: > >> > >> funcdef: ('def' NAME parameters ['->' test] ':' suite | > >> 'def' NAME parameters ['->' test] '{' suite '}' ) > >> > >> I reran Parser/pgen and the dfa changes, but python (3.1) when > recompiled, > >> throws errors on things like: > >> > >> def a() { None } > >> > >> Strangely enough: > >> > >> lambdef: ( 'lambda' [varargslist] ':' test | > >> 'lambda' [varargslist] '{' test '}' ) > >> > >> works fine! I this simplely some difference between "test" and "suite". > >> > >> I have tried tackling this with gdb, looking at err_input clearly isn't > >> enough. > >> > >> (gdb) break err_input > >> (gdb) break PyParser_ASTFromString > >> import sys > >> b = compile("def a() {pass}","sys.stdout","single") > >> # yet a simple grammar fix is enough for this! > >> c = compile("lambda x {None}","sys.stdout","single") > >> > >> I'm in over my head! > > > > You don't say what errors occur when you try to compile strings in > > your new language. You may have changed the Grammar, which allows you > > to tokenize the input. That isn't enough to get the input to compile. > > You also need to change the compiler to understand the new tokens. > > In particular, many AST creation functions check for specific counts of > children on many nodes. I haven't checked, but in the case of the > "funcdef" rule, it may check for either 7 or 5 children to determine > whether the optional return annotation ['->' test] is present. > > Georg > > > -- > Thus spake the Lord: Thou shalt indent with four spaces. No more, no less. > Four shall be the number of spaces thou shalt indent, and the number of thy > indenting shall be four. Eight shalt thou not indent, nor either indent > thou > two, excepting that thou then proceed to four. Tabs are right out. > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/gregg.lind%40gmail.com >
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