Come on, indulge us. Why do people say Lisp is slow?
Well, there are plenty of reasons. A: Lisp is old – almost 50. These days, lots of people mistake age for obsolescence. A: Some people associate Lisp with the old hardware it used to run on (the PDP-10 was a popular platform, I hear) A: Lisp is interactive, which a lot of people take to mean that Lisp is (always) interpreted. Early lisps (and others, like CLisp) are interpreted, although most modern lisps are compiled. A: Emacs Lisp, owing to the incredibly wide array of platforms to which it was eventually ported, used to be very slow for many users A: Lisp was used extensively for AI and simulation, fields full of hard computational problems. A: Lisp will a few bits of type information to values that it stores, so values don’t always fit neatly with machine words (this is the only legitimate reason in the list). A: For the previous two reasons, a lot of effort in the AI and Lisp communities went into producing custom hardware — Lisp Machines, or Lispms — in the mid 1980s. Some people
