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From: yoann padioleau <padator@wanadoo.fr>
Reply-To: yoann padioleau <padator@wanadoo.fr>
To: Andrej Bauer <andrej.bauer@andrej.com>, caml-list@inria.fr
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Subject: re: [Caml-list] ocamllex and python-style indentation
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Date: Thu, 11 Jun 2009 15:12:57 +0200 (CEST)
X-Spam: no; 0.00; ocamllex:01 lexer:01 parser:01 ocamllex:01 lexer:01 parser:01 ocaml:01 lexing:01 tokens:01 tokens:01 andrej:01 beginner's:01 ocaml:01 bug:01 beginners:01 


> My parsing powers are not sufficient to easily come up with
> lexer/parser for a simple language that uses python-style indentation
> and newline rules. Does anyone have such a thing lying around, written
> in ocamllex/yacc or menhir? I would appreciate a peek to see how
> you've dealt with it.
> 
> For example, suppose we want just a very simple fragment of Python
> involving True, False, conditional statements, variables, and
> assignments, such as:
> 
> if True:
> x = 3
> y = (2 +
> 4 + 5)
> else:
> x = 5
> if False:
> x = 8
> z = 2
> 
> How would I go about writing a lexer/parser for such a thing in ocaml?

I guess you could interpose a function between lexing and parsing that works on the tokens
and position information of those tokens to insert some new extra tokens that will then
make the job of the parser easier. For instance you could add some "virtual" ';' at the end
of each line except when you are in a parenthesized stuff.


> 
> Andrej
> 
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