[Caml-list] debugging ocamllex/ocamlyacc specifications?

[Caml-list] debugging ocamllex/ocamlyacc specifications?

[Will Benton]

Hello, all.  I am writing a simple interpreter for fun but am having
trouble with ocamllex and ocamlyacc.  To test my lexer and parser, I am
using the test program from the desk calculator example in the manual, but
I when I type in an expression and press EOL, it does nothing (my "main"
rule in the parser is "exp EOL"); I know it's doing something because
if I type in a garbage expression, it gives me a parse error
exception.  When I type in an expression and press EOF, on the other hand,
it gives me a Failure("lexing: empty token") exception.

If anyone knows what might cause these problems, that would be nice to
know.  Otherwise, if there is some way to put the lexer and parser in a
"verbose debug mode", detailing what tokens are produced and/or what
productions are applied, that would be really helpful.


thanks,
wb

---
Will Benton      | "Nicht wie die Welt ist, ist das Mystische, 
willb@acm.org    |  sondern daß sie ist." --L. Wittgenstein

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Re: [Caml-list] debugging ocamllex/ocamlyacc specifications?

[Markus Mottl]

On Fri, 28 Dec 2001, Will Benton wrote:
> Hello, all.  I am writing a simple interpreter for fun but am having
> trouble with ocamllex and ocamlyacc.  To test my lexer and parser, I am
> using the test program from the desk calculator example in the manual, but
> I when I type in an expression and press EOL, it does nothing (my "main"
> rule in the parser is "exp EOL"); I know it's doing something because
> if I type in a garbage expression, it gives me a parse error
> exception.

Maybe you only need to flush the output channel after printing results?

> When I type in an expression and press EOF, on the other hand,
> it gives me a Failure("lexing: empty token") exception.

I don't know what your parser looks like, but you might have to add an
appropriate rule for "EOF" so that it isn't considered as a parse error
anymore and quits the program instead.

Regards,
Markus Mottl

-- 
Markus Mottl                                             markus@oefai.at
Austrian Research Institute
for Artificial Intelligence                  http://www.oefai.at/~markus
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