ISO/IEC JTC1 SC22 WG17 Minutes via Zoom
Date of meeting: 2023-06-05
Time of meeting: 16:00 - 17:53 UTC

1. Greeting and introduction of participants, administrativa

WG17 members:
Klaus Däßler (Germany)
Stefan Kral (Austria)
Markus Triska (Austria)
Manuel Hermenegildo (Spain)
Mark Thom (Canada)
Ulrich Neumerkel (convener)

Invited non-member experts:
Adrian Arroyo Calle (Spain)
Yukata Ichibangase (Japan)
Jose Morales (Spain)
Fred Mesnard (France)

Not present, but registered:
Timothy Laine (USA)
Robin Rowe (USA)


Ad 1.1 Minutes of 2022 meeting N293 were approved.


Ad 1.2 Recent progress in Prolog systems.

Scryer: FFI by Adrian Arroyo Calle, inline caching of meta-calls

Ciao: WASM support

In general, some implementation still do not support succ/2 and other
predicates of the Prolog prologue.


1.3 Prolog 50.

Manuel Hermenegildo reports about the 50th anniversarty of Prolog on
November 10th in Paris.  More than 100 participants.  Slides, photos,
movies under

https://prologyear.logicprogramming.org/PrologDay.html


Ad 2 Further corrigenda.

The list stc was briefly reviewed up to #52. No
items requiring an urgent reaction were identified.

A formal notation for desired behaviour to be used in the standard
would be desirable.


Ad 3 Prolog prologue.

Agreement to add new entry foldl/4 .. as p.p.10.

Further themes with lesser priority are

i Syntactic inequality, dif/2.

An overview of current implementations with test cases is under

https://www.complang.tuwien.ac.at/ulrich/iso-prolog/dif

While there are several systems that support dif/2, not all systems
(like GNU) support it.  dif/2 thus cannot be part of the Prolog
prologue.  A separate work item may be considered in the future.

ii STO unification

While 13211-1 keeps STO unification undefined, several ways to handle
STO unification have emerged.  Many are based on rational trees,
others support optionally the occurs-check, some with errors. Another
rescent approach is based on pure syntactic substitutions (Tau).  All
agree on some case where 13211-1 remains undefined thus permitting to
reduce the undefined areas. A separate work item may be considered in
the future.

iii Unicode support

Need for better support of Unicode, in particular characters above
2^16 like the Unicorn.  Resolved A 1.


Ad 4 DCG progress.

Higher-order non-terminals were mentioned, but no strong opinion to
add phrase//2,...

Submission target is August 15th.


A Resolutions

A 1. Resolved to ask Markus Triska to prepare and submit an NWIP for a
TS "Unicode characters in quoted characters of Prolog text" as its editor.

A 2. WG17 requests SC22 approve this NWIP ballot.

A 3. Resolved to add foldl/4.. as p.p.10 to the Prolog prologue.

Meeting adjourned at 17:53 UTC.