Re: [m-users.] Compiler bug found

Volker Wysk <[email protected]> Fri, 24 Feb 2023 17:02:05 +0100
Newsgroups	gmane.comp.lang.mercury.general
Message-ID	<[email protected]>
Understood. Thanks for the explanation.

Volker

Am Freitag, dem 24.02.2023 um 11:41 +1300 schrieb Richard O'Keefe:
> Mercury's treatment of variables beginning with underscore
> follows Prolog closely.
> "_" all by itself is a "wild card" with each occurrence
> standing for a different variable.
> A variable that does not begin with underscore is expected
> to occur at least twice and a 'singleton variable' warning
> will be issued if this is not so.
> A variable (other than the wild card) that begins with an
> underscore is expected to occur exactly once and a warning
> will be issued if such a variable is repeated.
> 
> Historically it was important to be able to begin
> a variable with an underscore to mark it as a variable
> if you were using a terminal with a single case of
> letters.  Code like
> +append(_X, [_X,.._]).
> +append(_X, [_,.._L])-append(_X, _L).
> was not unusual.  To this day, if you are writing in a
> script that does not make a case distinction (such as
> Chinese or Japanese) you need to be able to prefix a
> word in your language with an underscore to make it a
> variable WITHOUT turning it into a wildcard.
> 
> 
> On Fri, 24 Feb 2023 at 07:19, Volker Wysk <[email protected]> wrote:
> > Am Freitag, dem 24.02.2023 um 02:15 +1100 schrieb Zoltan Somogyi:
> > > A variable token consisting of single underscore is treated specially:
> > > each instance of @samp{_} denotes a distinct variable.
> > > 
> > > It does NOT say that *every* variable that starts with an underscore
> > denotes
> > > a distinct variable. 
> > 
> > Hmm... I thought it does. Maybe it's like that in Prolog.
> > 
> > Cheers,
> > Volker
> > _______________________________________________
> > users mailing list
> > [email protected]
> > https://lists.mercurylang.org/listinfo/users

_______________________________________________
users mailing list
[email protected]
https://lists.mercurylang.org/listinfo/users
signature.asc (application/pgp-signature, 833 B)