The short eval is standard amongst small lisps (see eg SICP), but the immutability which leads to the nice ABC GC (no RPLACD, no cycles, immutable strings) is

The short eval is standard amongst small lisps (see eg SICP), but the immutability which leads to the nice ABC GC (no RPLACD, no cycles, immutable strings) is practical. All other lisp liked one or our autolisp features: the very same immutability. Such a GC really is trivial and fast. Lot of temporary garbage, but only for a single op.