From e6a38aa97b9de05ae0eede568212667b68784a60 Mon Sep 17 00:00:00 2001
From: Peter Mikkelsen <peter@pmikkelsen.com>
Date: Wed, 7 Jul 2021 16:44:25 +0000
Subject: Add copy_term/2

---
 builtins.c | 14 ++++++++++++++
 dat.h      |  1 +
 eval.c     |  4 ----
 main.c     |  1 +
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/builtins.c b/builtins.c
index 5751502..95b6438 100644
--- a/builtins.c
+++ b/builtins.c
@@ -32,6 +32,7 @@ BuiltinProto(builtincompare);
 BuiltinProto(builtinfunctor);
 BuiltinProto(builtinarg);
 BuiltinProto(builtinuniv);
+BuiltinProto(builtincopyterm);
 BuiltinProto(builtinis);
 BuiltinProto(builtincatch);
 BuiltinProto(builtinthrow);
@@ -98,6 +99,8 @@ findbuiltin(Term *goal)
 		return builtinarg;
 	if(Match(L"=..", 2))
 		return builtinuniv;
+	if(Match(L"copy_term", 2))
+		return builtincopyterm;
 	if(Match(L"is", 2))
 		return builtinis;
 	if(Match(L"catch", 3))
@@ -461,6 +464,17 @@ builtinuniv(Term *goal, Binding **bindings, Module *module)
 	}
 }
 
+int
+builtincopyterm(Term *goal, Binding **bindings, Module *module)
+{
+	USED(module);
+	Term *term1 = goal->children;
+	Term *term2 = term1->next;
+	Term *t = copyterm(term1, &clausenr);
+	clausenr++;
+	return unify(term2, t, bindings);
+}
+
 #define ToFloat(t) (t->tag == IntegerTerm ? (double)t->ival : t->dval)
 
 Term *
diff --git a/dat.h b/dat.h
index 1bde347..6e93b84 100644
--- a/dat.h
+++ b/dat.h
@@ -97,3 +97,4 @@ Goal *goalstack;
 Module *modules;
 Module *systemmodule; /* The module for the builtins. Everything has access to those */
 Module *usermodule; /* The default module for user defined predicates */
+uvlong clausenr;
\ No newline at end of file
diff --git a/eval.c b/eval.c
index 6c20a7e..3201286 100644
--- a/eval.c
+++ b/eval.c
@@ -12,8 +12,6 @@ Goal *copygoals(Goal *);
 Builtin findbuiltin(Term *);
 void addchoicepoints(Clause *, Term *, Goal *, Module *);
 
-static uvlong clausenr;
-
 int
 evalquery(Term *query, Binding **resultbindings)
 {
@@ -39,8 +37,6 @@ evalquery(Term *query, Binding **resultbindings)
 		/* Now add the actual goals */
 		goalstack = addgoals(goalstack, query, usermodule);
 
-		clausenr = 2; /* Start at two since 0 is for the facts in the database, and 1 is for queries */
-
 	}else{
 		goto Backtrack;
 	}
diff --git a/main.c b/main.c
index 7c1b1ca..f97a466 100644
--- a/main.c
+++ b/main.c
@@ -18,6 +18,7 @@ main(int argc, char *argv[])
 		usage();
 	}ARGEND
 
+	clausenr = 2; /* Start at two since 0 is for the facts in the database, and 1 is for queries */
 	initflags();
 	initstreams();
 	initmodules();
-- 
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