Re: indentations instead of endtag in a grammar

[Andreas Wagner]

Hi Conrad,

very much thx for your answer and the link to the parathon.l file. I think
this could help me a lot. Im not trying to parse Phyton-code. I have a
language which is "python-like" cause of the line indentations.

Regards

2010/2/17 Conrad Irwin <address@hidden>

>
>
> On 02/17/2010 02:22 PM, Andreas Wagner wrote:
> > Thx for your fast answers. I will take a look.
> > @ Istvan is it possible that u send me the *.l & *.y files for python
> > (if u have them)?
> > Or post a link. Always when i search for python and .y or bison i just
> > find links to PyBison or PLY but no bison and lex file for Python.
> >
>
> Real Python has a hand-coded tokenizer and their own parser generator,
> probably explaining why you haven't found what you were looking for
> (though downloading the source code would tell you that pretty quickly).
>
> As part of a recent project, I implemented a lexer for Python [1]; as it
> runs is a fairly complex environment (and I'm rubbish at writing C), you
> won't be able to compile it, but the ideas are copyable. The bison
> parser is auto-generated from some C++ class files, so it's not terribly
> illuminating either, an excerpt:
>
> if_statement: TOK_IF test_phrase TOK_COLON suite {
>                $$ = IfStatement::parse($1, $2, $3, $4); }
>            | if_statement TOK_ELSE TOK_COLON suite {
>                $$ = IfStatement::parse($1, $2, $3, $4); }
>            ;
> suite: simple_statement TOK_NEWLINE {
>        $$ = Suite::parse($1, $2); }
>     | TOK_NEWLINE TOK_INDENT suite_body TOK_OUTDENT {
>        $$ = Suite::parse($1, $2, $3, $4); }
>     ;
>
> Note that in addition to keeping a stack of indentation levels, the
> lexer also keeps track of open brackets, as a newline inside a bracket
> does not count as significant in Python (nor a newline after a \).
>
> Yours
> Conrad
>
> [1] http://jelzo.com/got/181/parathon.l A lexer for Python(ish).
>
>
>
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