debugging scheme module

debugging scheme module

[Al Nikolov]

Hello, all!

I'm totally newbie in Guile and R5RS, faced to write a scheme module for an
application written with Guile.

When i do just another wierd mistake and run the app, i usually get
uncomprehensive error messages like:

Fatal error: [library-name] wrong-type-arg: ("caddar" "Wrong type argument
in position ~A: ~S" (1 ()) #f)

Since my scheme code is bigger than two parenthesis and three lines, i
feel myself totally embarassed by having absolutely no idea where to look
for the trouble and what those "~A"s and "#f"s mean.

Could anybody be so kind to give me directions to fight my ignorance?

-- 
Regards,
Al Nikolov       jid: alnikolov@jabber.ru irc: clown uin: 312108671
pgp fingerprint: 4B50 F1E3 080C 21A2 91F4  8BF0 CD60 3B5A 2ECF 984B


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Re: debugging scheme module

[Ludovic Courtès]

Hi,

Al Nikolov <al@iac.spb.ru> writes:

> Fatal error: [library-name] wrong-type-arg: ("caddar" "Wrong type argument
> in position ~A: ~S" (1 ()) #f)

This means that at some point, `caddar' is invoked and is passed `#f'
instead of a list.  :-)

> Since my scheme code is bigger than two parenthesis and three lines, i
> feel myself totally embarassed by having absolutely no idea where to look
> for the trouble and what those "~A"s and "#f"s mean.

You could try the following:

  (read-enable 'debug)
  (debug-enable 'debug)

This has to be done early enough, ideally when Guile starts up (or when
your first Scheme file gets read).  If you use 1.8, then it should show
a complete backtrace instead of just an error line.

Alternatively, you can run `guile' with the `--debug' option (if that is
an option for you).

Hope this helps,
Ludovic.


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Re: debugging scheme module

[Neil Jerram]

ludovic.courtes@laas.fr (Ludovic Courtès) writes:

> You could try the following:
>
>   (read-enable 'debug)
>   (debug-enable 'debug)

I believe that should be:

   (read-enable 'positions)
   (debug-enable 'debug)
   (debug-enable 'backtrace)

Regards,
     Neil



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