[m-dev.] proposed command set for the internal trace based debugger

[Peter Schachte]

> > Wouldn't it be possible to have a debug version of the library that
> > makes file opening and closing commands "trail" their effects so they
> > can be redone?
> 
> This is all a good idea; are you volunteering to implement it? ;-)

If someone volunteers to pay me. ;-)

> > One other command that would be useful (if it's implementable) would
> > be to replace the goal at the current port with one the user types in.
> 
> I don't think this would be very useful, especially in comparison to the
> likely difficulty of implementation.

I can't comment on the difficulty, but I know I've wanted it plenty of times
in debugging Prolog code.

> > You seem to have omitted the REDO port.  That one's pretty important.
> 
> Our execution mechanism optimizes away the REDO port.
> Instead, execution jumps directly to the place where execution will
> resume (i.e. a DISJ port).  

That sounds like what you should show, then.  But how is this different from
a REDO port anyway?  Let me put it this way:  I don't want to step through a
hundred redo-fail pairs.  Arriving immediately at the first REDO port that
has a chance of succeeding is fine with me.  That's what the Quintus
debugger does, too. 


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