[m-users.] Free and Ground in the same error line?

[Sean Charles (emacstheviking)]

DCG-s are a hard habit to break for me, from Prolog abuse I guess.


> On 28 Oct 2023, at 12:05, Zoltan Somogyi <zoltan.somogyi at runbox.com> wrote:
> 
> 
> On 2023-10-28 21:53 +11:00 AEDT, "Volker Wysk" <post at volker-wysk.de> wrote:
>> I have the impression that the compiler often gives complicated error
>> messages for stupid errors...
> 
> The two main factors influencing whether the compiler will have a direct,
> specific error message for a class of errors are
> 
> - how frequent that class of errors appears to be, and
> - how difficult that class of errors is to isolate from other classes.
> 
> It is a sad fact of life that the people judging the frequency
> of error classes are the compiler developers. Since their errors
> have a different frequency distribution from other language users,
> the work they (we) put into improving error messages usually
> benefits us more than it benefits general users. That said, we of course
> do try to improve messages even for errors we don't encounter
> ourselves. (For example, I wouldn't encounter this bug, because
> I stopped using DCGs ages ago.) Of course, this does require that
> such problems be brought to our attention. That usually works;
> for example, I extended the error message mmc generates
> for references to undefined types, predicates etc with "did you mean"
> suggestions (such as "circle" for "cirle") a few days after the m-users
> thread about that error.
> 
> So if you get a complicated error message for an error, stupid or not,
> you know what to do.
> 
> Zoltan.