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ENHANCED: Improve determinism of ... //0 and seq//1.

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Example:

    ?- phrase(..., "hello").
       true.

This addresses #1577.
This commit is contained in:
Markus Triska
2022-08-21 14:29:32 +02:00
committed by Mark Thom
parent 8a9cd7779c
commit 47892bf24a
1 changed files with 13 additions and 0 deletions
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13
src/lib/dcgs.pl
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@@ -132,16 +132,29 @@ user:term_expansion(Term0, Term) :-
dcg_rule(Term0, Term). dcg_rule(Term0, Term).
% Describes a sequence % Describes a sequence
seq(Xs) -->
call(det_end_(Xs)),
!.
seq([]) --> []. seq([]) --> [].
seq([E|Es]) --> [E], seq(Es). seq([E|Es]) --> [E], seq(Es).
det_end_(Xs, Cs0,Cs) :-
var(Xs),
Cs0 == [],
Xs = [],
Cs0 = Cs.
% Describes a sequence of sequences % Describes a sequence of sequences
seqq([]) --> []. seqq([]) --> [].
seqq([Es|Ess]) --> seq(Es), seqq(Ess). seqq([Es|Ess]) --> seq(Es), seqq(Ess).
% Describes an arbitrary number of elements % Describes an arbitrary number of elements
... --> call(det_end), !.
... --> [] | [_], ... . ... --> [] | [_], ... .
det_end(Cs0,Cs) :-
Cs0 == [],
Cs0 = Cs.
error_goal(error(E, must_be/2), error(E, must_be/2)). error_goal(error(E, must_be/2), error(E, must_be/2)).
error_goal(error(E, (=..)/2), error(E, (=..)/2)). error_goal(error(E, (=..)/2), error(E, (=..)/2)).