1) Implement a breadth-first traversal of forward references 2) implement entity instance deletion from a file 3) recursively copy entity instances to another file

src/ifcparse/IfcSIPrefix.h

@@ -0,0 +1,29 @@
+/********************************************************************************
+ *                                                                              *
+ * This file is part of IfcOpenShell.                                           *
+ *                                                                              *
+ * IfcOpenShell is free software: you can redistribute it and/or modify         *
+ * it under the terms of the Lesser GNU General Public License as published by  *
+ * the Free Software Foundation, either version 3.0 of the License, or          *
+ * (at your option) any later version.                                          *
+ *                                                                              *
+ * IfcOpenShell is distributed in the hope that it will be useful,              *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of               *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                 *
+ * Lesser GNU General Public License for more details.                          *
+ *                                                                              *
+ * You should have received a copy of the Lesser GNU General Public License     *
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.         *
+ *                                                                              *
+ ********************************************************************************/
+
+#ifndef IFCSIPREFIX
+#define IFCSIPREFIX
+
+#include "../ifcparse/IfcParse.h"
+
+namespace IfcParse {
+	double IfcSIPrefixToValue(IfcSchema::IfcSIPrefix::IfcSIPrefix v);
+}
+
+#endif