fix bug

interpreter/code.c

@@ -395,7 +395,7 @@ void exec(Code* expr, int frame_ptr, int root_frame_ptr)
                     (*bt)->_args[i]->desc->eval();
                 }
 
-                int argmask = 1;            
+                int argmask = 1 << (*bt)->desc->arity;  
 
                 for (int i = 0; i < expr->nr_args; i++) {