[m-rev.] for review: field names and higher order values in the debugger

[Fergus Henderson]

On 18-Dec-2001, Zoltan Somogyi <zs at cs.mu.OZ.AU> wrote:
> 
> Allow the browser to refer to fields by name, and allow the debugger to print
> higher order values.

It would be better to handle those as two separate changes.

> library/std_util.m:
> 	Add new predicates named_argument and det_named_argument. They are
> 	implemented using ML_named_arg, a new C function which is the same
> 	as ML_arg except that it specifies the selected argument by name.

These should be mentioned in the NEWS file.

> runtime/mercury_ml_expand_body.h:
> 	Add a new alternative, EXPAND_NAMED_ARG, for use in implementing
> 	ML_named_arg.
> 
> 	Deconstruct closures as if they were ordinary terms, with the function
> 	symbol being the name of the predicate/function and the arguments being
> 	the terms stored in the closure.

Allowing deconstruction of closures breaks referential transparency for
std_util__deconstruct and the like.

> +++ runtime/mercury_ml_expand_body.h	2001/12/18 03:33:42
> @@ -549,8 +621,88 @@
>  
>          case MR_TYPECTOR_REP_PRED:
>              /* XXX expand_info->non_canonical_type = TRUE; */

After your change, the code inside the comment there is needed.

> std_util.m:
> +	% named_argument(Data, ArgumentName) = ArgumentUniv
> +	%
> +	% Same as argument, except the chosen argument is specified by giving

s at argument@argument/2@

> +	% det_named_argument(Data, ArgumentName) = ArgumentUniv
> +	%
> +	% Same as named_argyment/2, except that for cases where

s/y/u/

> +:- pragma foreign_proc("C#",
> +        named_argument(_Term::in, _ArgumentName::in) = (_ArgumentUniv::out),
> +        [will_not_call_mercury], "
> +{
> +	mercury.runtime.Errors.SORRY(""foreign code for argument"");
> +	// XXX this is required to keep the C# compiler quiet
> +	SUCCESS_INDICATOR = false;
> +}").

It would be better to write that as Mercury code,
like I did in private_builtin.m.

> +++ runtime/mercury_ml_expand_body.h	2001/12/18 03:33:42
> @@ -43,6 +43,10 @@
>  **                          argument, chosen, and it will fill in the fields
>  **                          of the ML_Expand_Chosen_Arg_Only structure.
>  **
> +** EXPAND_NAMED_ARG         If defined, the function will have an extra
> +**                          argument, chosen_name, and it will fill in the
> +**                          fields of the ML_Expand_Chosen_Arg_Only structure.

The documentation should explain the semantics of the extra argument.

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