[m-dev.] for review: improve DD user interface

[Fergus Henderson]

On 20-Feb-2000, Mark Anthony BROWN <dougl at cs.mu.OZ.AU> wrote:
> Fix the user interface of the declarative debugger so that it
> produces more readable output; the representation of atoms
> is updated so that it can handle non-ground arguments.

That change looks fine to me.

> +confirm_bug(Store, Bug, Response, Diagnoser0, Diagnoser) -->
> +	{
> +		Bug = e_bug(Node),
> +		Message = "Incorrect node found:\n"
> +	;
> +		Bug = i_bug(Node),
> +		Message = "Inadmissible call node found:\n"
> +	},

I'm not sure that "node" is the ideal term to describe
these things to the user.

> +++ browser/declarative_execution.m	2000/02/20 05:48:31
> @@ -92,20 +92,16 @@
>  		)
>  	.
>  
> -	% If either of the following two types are modified, some of
> -	% the macros in trace/mercury_trace_declarative.h may need
> -	% to be updated.
> -	%
>  :- type trace_atom
>  	--->	atom(
>  			string,			% Procedure name.
> -			list(univ)		% Arguments.
> -			% XXX we also need to store some information about
> -			% where the arguments come from, since they will
> -			% not necessarily be in the right order or all
> -			% present (we do not store unbound variables).
> +			list(maybe(univ))	% Arguments.
>  		).

Please put an XXX there saying that this representation
won't handle partially instantiated data structures.

> +:- func construct_trace_atom(string, int) = trace_atom.
> +:- pragma export(construct_trace_atom(in, in) = out,
> +		"MR_DD_construct_trace_atom").
> +
> +construct_trace_atom(Functor, Arity) = atom(Functor, Args) :-
> +	list__duplicate(Arity, no, Args).
> +
> +:- func add_trace_atom_arg(trace_atom, int, univ) = trace_atom.
> +:- pragma export(add_trace_atom_arg(in, in, in) = out,
> +		"MR_DD_add_trace_atom_arg").
> +
> +add_trace_atom_arg(atom(F, Args0), Num, Val) = atom(F, Args) :-
> +	list__replace_nth_det(Args0, Num, yes(Val), Args).

That is not a particularly efficient way of constructing
a list -- for N arguments it's O(N^2).
However, I suppose it probably doesn't matter
(that's not in the inner loop, right?).

> +:- pred user_confirm_bug_help(user_state, io__state, io__state).
> +:- mode user_confirm_bug_help(in, di, uo) is det.
> +
> +user_confirm_bug_help(user(_, OutStr)) -->
> +	io__write_strings(OutStr, [
> +		"Answer one of:\n",
> +		"\ty\tyes\t\tconfirm that the suspect is a bug\n",
> +		"\tn\tno\t\tdo not accept that the suspect is a bug\n",
> +%		"\tb\tbrowse\t\tbrowse the suspect\n",
> +		"\ta\tabort\t\tabort this diagnosis session\n",
> +		"\th, ?\thelp\t\tthis help message\n"
> +	]).

Does the abort command return to the mdb prompt?
If so, it might be a good idea to mention that
to the explanation above.

> +/*
> +** If the variable specified by n is a head variable, then return
> +** its argument position, otherwise return an error.
> +*/
> +
> +extern	const char	*MR_trace_headvar_num(int n, int *num);

The comment here is potentially misleading: you don't return the
argument position, you store the argument position in *num and return
NULL.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.
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