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From: Mild Shock <janburse@fastmail.fm>
Newsgroups: comp.lang.prolog
Subject: Re: Is a PIP for Syntax extensions necessary? (Was; post-N246 Read-
 and Write-Option variable_names/1)
Date: Sun, 11 Aug 2024 00:05:15 +0200
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Anything that touches or depends on syntax
is a complete can of worms. The ISO commitee
was not able to find an initial *english natural

language specification wording* for character
look-ahead, so that we find now character
look-ahead in Prolog compounds practially

implemented by all Prolog systems, but character
look-ahead interpretation may differ for
negative numbers, like here:

/* SWI-Prolog */
?- X = - 1^2, write_canonical(X), nl.
-(^(1,2))

/* Scryer Prolog */
?- X = - 1^2, write_canonical(X), nl.
^(-1,2)

But in the case of Scryer Prolog it doesn't
matter, since Scryer Prolog is anyway dead.

Mild Shock schrieb:
> I have a question, does SWI-Prolog not anymore use
> their dict syntax in the Janus interface:
> 
>  > import janus_swi as janus
>  > janus.query_once("Y is X+1", {"X":1})
> {'Y': 2, 'truth': True}
> 
> I don’t see _{...} anymore. When and how did this
> happen? I was just thinking whether a Syntax
> extension PIP is necessary. Such a PIP isn’t listed:
> 
> https://prolog-lang.org/ImplementersForum/PIPs.html
> 
> Is SWI-Prolog safe, against parsing problems,
> when it still has block operators in the
> background? Like can one mix and match
> 
> code that uses Janus interface with the
> “new” dicts with other code that uses the
> SWI-Prolog dicts based on _{...}
> 
> which we might now term the “old” dicts.
> How do you access and manipulate the
> “new” dicts, do the “old” operations work?