I think it's easier to reason about in the long run although the initial period of wondering why you don't just set up a data structure and bang on it in place

I think it's easier to reason about in the long run although the initial period of wondering why you don't just set up a data structure and bang on it in place is a little bumpy. The syntax is always[0] (procedure argument-1 argument-2 ...) where the procedure is applied to the arguments. about half-hour in to this lecture the syntax is explained: http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-001-structure-and-interpretation-of-computer-programs-spring-2005/video-lectures/1a-overview-and-introduction-to-lisp/ http://ocw.mit.edu/courses/electrical-engineering-and-comput... [0] - almost always. Macros look the same and often get treated the same but they are very different.