1 files changed, 17 insertions, 0 deletions
diff --git a/builtins.c b/builtins.c
index 35db61a..5751502 100644
--- a/builtins.c
+++ b/builtins.c
@@ -409,6 +409,23 @@ builtinuniv(Term *goal, Binding **bindings, Module *module)
 	Term *term = goal->children;
 	Term *list = term->next;
 
+	if(term->tag == VariableTerm && ispartiallist(list))
+		Throw(instantiationerror());
+	if(!(ispartiallist(list) || islist(list)))
+		Throw(typeerror(L"list", list));
+
+	Term *head = listhead(list);
+	Term *tail = listtail(list);
+
+	if(term->tag == VariableTerm && head->tag == VariableTerm)
+		Throw(instantiationerror());
+	if(islist(list) && !(head->tag == AtomTerm || head->tag == VariableTerm) && !isemptylist(tail))
+		Throw(typeerror(L"atom", head));
+	if(islist(list) && head->tag == CompoundTerm && isemptylist(tail))
+		Throw(typeerror(L"atomic", head));
+	if(term->tag == VariableTerm && isemptylist(list))
+		Throw(domainerror(L"non_empty_list", list));
+
 	int len;
 	if(term->tag == VariableTerm){
 		Rune *name;