[m-dev.] grades & options for tracing and debugging

[Zoltan Somogyi]

> > So a recursive call will have
> > a call port but no corresponding exit port:
> 
> If we were going to do it that way, then I think it would
> be better to add a new "tailcall" port.

One purpose of tracing is to enable trace analysis by simple scripts
written by the programmer. Anything that makes such scripts more complicated
to write will actually reduce programmer productivity, not increase it.
Breaking the rule that every success leads to an exit event would
certainly increase complexity.

Therefore while a tailcall port may make sense when using the internal
debugger, it does *not* make sense when using the external debugger.

Zoltan.