It needs to be said very firmly that LISP, at least as represented by the dialects in common use, is not a functional language at all. LISP does have a functional subset, but that is a rather inconvenient programming language and there exists no significant body of programs written in it. Almost all serious programming in LISP makes heavy use of side effects and other referentially opaque features.

I think that the historical importance of LISP is that it was the fi rst language to provide ‘garbage- collected’ heap storage. This was a very important step forward. For the development of functional programming , however, I feel that the contribution of LISP has been a negative one. My suspicion is that the success of LISP set back the development of a properly functional style of programming by at least ten years.