From: Markus Triska <triska@metalevel.at>
Date: Sat, 3 Jul 2021 07:54:01 +0000 (+0200)
Subject: ADDED: ... //0, describing an arbitrary number of elements
X-Git-Tag: v0.9.0~51^2
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=bf9654e1383c11be80746da5a4dc9e0fd37fed4b;p=scryer-prolog.git

ADDED: ... //0, describing an arbitrary number of elements

This is a very versatile nonterminal. For instance, repeated elements:

    ?- phrase((...,[E],...,[E],...), "hello!!").
    %@    E = l
    %@ ;  E = !
    %@ ;  false.
---

diff --git a/src/lib/dcgs.pl b/src/lib/dcgs.pl
index e1751d8c..f4cee25c 100644
--- a/src/lib/dcgs.pl
+++ b/src/lib/dcgs.pl
@@ -3,7 +3,9 @@
 		   phrase/2,
 		   phrase/3,
                    seq//1,
-                   seqq//1]).
+                   seqq//1,
+                   ... //0
+           ]).
 
 :- use_module(library(error)).
 :- use_module(library(lists), [append/3]).
@@ -188,3 +190,6 @@ seq([E|Es]) --> [E], seq(Es).
 % Describes a sequence of sequences
 seqq([]) --> [].
 seqq([Es|Ess]) --> seq(Es), seqq(Ess).
+
+% Describes an arbitrary number of elements
+... --> [] | [_], ... .