Because this guide is a basic “getting started” manual, other resources are required to fill in the blanks. This document was never intended to be a comprehensive guide to learning GDL, since there are already so many great resources for that. My intention in writing this is to introduce and encourage those who are too intimidated to learn a scripting language required to take the leap into creating parametric objects. When the sections of this document become easy and you need to learn more, here are some great resources:
GRAPHISOFT GDL Reference Guide
Self GDL (Site is in German, use web translator or learn German)