[m-dev.] for review: provide feedback when changing levels

[Fergus Henderson]

On 13-Nov-1998, Zoltan Somogyi <zs at cs.mu.OZ.AU> wrote:
> 
> Provide feedback for the "up", "down" and "level" commands in the debugger,
> in the form of a line from an enhanced stack dump.

That looks fine.  Please commit it.

Actually I do have some comments, but I don't think are worth holding up
the release for.  I would prefer it if you commit this as is,
then commit the debugger documentation changes that are holding up
the release, and then worry about addressing these comments.

...
>  mdb> level 1
> +   1       5       4    3 pred queens:qperm/2-0 (nondet) 
>  Ancestor level set to 1.

The output is rather confusing, since it's not clear what
the various different numbers mean.  Printing a `:' after the
event number might help a bit, since that would make it a bit
more like the ordinary tracing display.
But it might actually be clearer to just print the level number and
the procedure name/arity/mode/detism and leave out the
event number, call number, and depth.

Likewise, the output of the `stack --detailed' command is also rather
confusing:

> +mdb> stack -d
> +   0      20      10    6 pred queens:qperm/2-0 (nondet)
> +   1      15       8    5 pred queens:qperm/2-0 (nondet)
> +   2      10       6    4 pred queens:qperm/2-0 (nondet)
> +   3       5       4    3 pred queens:qperm/2-0 (nondet)
> +   4       4       3    2 pred queens:queen/2-0 (nondet)
> +   5       1       1    1 pred queens:main/2-0 (cc_multi)

Some headings here would help.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "Binaries may die
WWW: <http://www.cs.mu.oz.au/~fjh>  |   but source code lives forever"
PGP: finger fjh at 128.250.37.3        |     -- leaked Microsoft memo.