> Lisp hackers create works of art that no one else can figure out after they leave. It's possible, but it's not necessarily so. There are many Lisp code bases

> Lisp hackers create works of art that no one else can figure out after they leave. It's possible, but it's not necessarily so. There are many Lisp code bases which are 20, 30, 40 or even 50 years old and still maintained, passing on the work to new generations of programmers. Maxima has bits from the end 60s. Cyc is under continuous development from the early 80s onwards. SBCL is based on Spice Lisp code developed at CMU from 1981. The commercial implementations Allegro CL and LispWorks with their IDEs and libraries are under development since mid/end 80s. Axiom/Fricas computer algebra systems started the code base in the 70s at IBM as Scratchpad 2. The first MIT LOOP macro implementation was written in the 70s and then modified as Lisp dialects changed. The G2 process control system by Gensym started mid/end 80s and is still being sold. The SPIKE telescope scheduling system from NASA is still in use for various large earth and space telescopes - originally development started in the end 80s. I've seen code bases which I could not understand from looking at them - rare, though. The biggest problems were code bases which were tied to a particular implementation and OS. For example the Sk8 multimedia development environment written by Apple is non-portable, since the Lisp code uses Mac native graphics/multimedia libraries everywhere directly from Lisp and is not abstracted in a layer.