Lisp: Functions, Recursion, and Lists

Lisp is the medium of choice for people who enjoy free style and flexibility. Gerald J. Sussman A Lisp programmer knows the value of everything, but the cost of nothing. Alan Perlis Lisp is a historically important language that is good for illustrating a number of general points about programming languages. Because Lisp is very different from procedure-oriented and object-oriented languages you may use more frequently, this chapter may help you think about programming in a different way. Lisp shows that many goals of programming language design can be met in a simple, elegant way. LISP HISTORY The Lisp programming language was developed at MIT in the late 1950s for research in artificial intelligence (AI) and symbolic computation. The name Lisp is an acronym for the LIS t P rocessor. Lists comprise the main data structure of Lisp. The strength of Lisp is its simplicity and flexibility. It has been widely used for exploratory programming, a style of software development in which systems are built incrementally and may be changed radically as the result of experimental evaluation. Exploratory programming is often used in the development of AI programs, as a researcher may not know how the program should accomplish a task until several unsuccessful programs have been tested. The popular text editor emacs is written in Lisp, as is the linux graphical toolkit gtk and many other programs in current use in a variety of computing environments.