Subject: Re: Q about GUI tracer

From: Jan Wielemaker <[email-masked]>
Date: Fri, 10 Nov 2000 09:56:07 +0100

On Fri, 10 Nov 2000, [email-masked] wrote:
>Hi!
>I've just tried GUI tracer for debugging prolog and found it very usefull,
>but i have some questions:
>
>There is some difference between hot-keys in gui-tracer and native pl-tracer,
>why?

Because the view is a little different.  In the normal tracer you are
looking at the now-running predicate, while in the GUI tracer you are
looking at the parent calling the now-running predicate.  This resulted
in a slightly different command-set with the resulting hotkey bindings.

>And how can i pass 'fail' and 'ignore' commands to my debugging program from
>gui-tracer?

At the moment you can't.  Just have a look at the source and I think
you'll be able to sort out how to add it.  Additions and improvements
are welcome.  Comments too, but don't really expect this thing to be
as fool-proof as the Prolog environment itself.  I generally use it
to figure out non-determinism problems.

I must admit I only use it `now-and-then' for real debugging.  In
practice I see myself using trace/1 quite often, spy or inserting a
call to trace/0 and look around using the normal tracer for a few
calls as well. I use full-blown stepping around only in exceptional
cases on my own code and a little more often on code from other people.
(though I hardly ever poke around in code I receive to reproduce
bugs).

There is already some stuff on the twiki web on this.  There is a
good point extending that.

	Cheers --- Jan