I didn't try macroexpanding it yet, but when I make the 9 a runtime-parameter, I eventually get a stack-overflow with SBCL not TCO-ing the "H" binding in labels

I didn't try macroexpanding it yet, but when I make the 9 a runtime-parameter, I eventually get a stack-overflow with SBCL not TCO-ing the "H" binding in labels. The comments make me think this is ported from scheme, which has precise TCO rules. [edit] macroexpanded: (LABELS ((H-37 (US-38) (IF (NULL US-38) NIL (LET ((FILE (CAR US-38)) (US1-39 (CDR US-38))) (LABELS ((H-43 (US-44) (IF (NULL US-44) (H-37 US1-39) (LET ((RANK (CAR US-44)) (US1-45 (CDR US-44))) (CONS (FORMAT NIL "~a~a" FILE RANK) (H-43 US1-45)))))) (H-43 RANKS)))))) (H-37 FILES))