Hello all. My apologies for this not being math related. On the PDP-1, Lisp did not seem to have the compositions of CAR and CDR (namely CAAR, CADR, CDAR, CAAAR, ...), as far as documentation goes. The PDP-6 seemed to indeed have these functions. I am wondering if any Lisps which pre-date the PDP-6 had these functions. I ask for historical clarity. Google isn't helping me much. Thanks, Robert Smith I took McCarthy's 6.41 freshman elective in Spring '62, and am almost certain the IBM 709/7090 had them then. I consider this quite math-related. To make it more so, the earliest Lisps had no numeric type--you represented integers with binary lists of Ts and NILs! --rwg