From: Mark Thom <markjordanthom@gmail.com>
Date: Thu, 11 Oct 2018 03:30:40 +0000 (-0600)
Subject: fix DCG bugs
X-Git-Tag: v0.8.110~334
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=24a72060215470ca9e55016227c352a255a21e3e;p=scryer-prolog.git

fix DCG bugs
---

diff --git a/README.md b/README.md
index 7fb1e25e..16e6341c 100644
--- a/README.md
+++ b/README.md
@@ -158,6 +158,7 @@ The following predicates are built-in to rusty-wam.
 * `numbervars/2`
 * `once/1`
 * `partial_string/2`
+* `phrase/{2,3}`
 * `rational/1`
 * `read/1`
 * `repeat/0`
diff --git a/src/prolog/lib/dcgs.pl b/src/prolog/lib/dcgs.pl
index 6ff86a79..bbb9f5d2 100644
--- a/src/prolog/lib/dcgs.pl
+++ b/src/prolog/lib/dcgs.pl
@@ -41,11 +41,12 @@ term_expansion(Term0, (ModHead :- ModBody)) :-
     nonvar(Body),
     expand_body(Body, ModBody, 0, N).
 
-expand_body((Term, Terms), (ModTerm, ModTerms), N0, N) :-
-    !, expand_body_term(Term, ModTerm, N0, N1),
+expand_body(Term0, (ModTerm, ModTerms), N0, N) :-
+    nonvar(Term0), Term0 = (Term, Terms), !,
+    expand_body_term(Term, ModTerm, N0, N1),
     expand_body(Terms, ModTerms, N1, N).
-expand_body(Term, ModTerm, N0, N) :-
-    expand_body_term(Term, ModTerm, N0, N).
+expand_body(Term0, ModTerm, N0, N) :-
+    nonvar(Term0), expand_body_term(Term0, ModTerm, N0, N).
 
 expand_body_term([], true, N, N) :- !.
 expand_body_term([Arg|Args], ModTerm, N0, N) :-