Skill++ is integrated into Skill. I actually mostly program in Skill++, but distinction is lost on my fellow engineers anyway, who don't even understand the code == list concept. Skill++ is based on Scheme while Skill is based on an old Lisp, Franz Lisp I think, with dynamic binding. Skill can call into Skill++ and vice versa; Skill is a Lisp-2 while Skill++ is a Lisp-1; the namespace used in Skill++ is the function namespace of Skill.