CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp Introducing Lisp The dominant programming language for experimental AI systems Lisp strengths: Interactive Supports symbolic computation Programs and data share a common representation Automatic management of memory Simple syntax Multiparadigm (functional, imperative, object-oriented) Supported by a long history and wide literature Also used as an internal scripting language for Gnu Emacs, Autocad, and other packages. CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp LISP = LISt Processing Intended for processing symbolic information Implementations from noncommercial sites: GNU Common Lisp (GCL) - U of Texas mods to Kyoto Common Lisp CLISP -- developed in Germany. Available implementations from www.franz.com: Allegro Common Lisp for Windows, Web edition. Allegro Common Lisp for Linux CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp LISP: Our Objectives Motivation and History Interactive programming Functional programming List manipulation with recursive functions Language extensibility via macro definitions Language evolution to support multiple paradigms Lisp look and feel Lisp for rapidly prototyping AI systems Lisp on the Web CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

History of Lisp (continued) John McCarthy, developed the ideas during the Dartmouth Summer Research Project on Artificial Intelligence, 1956. First implementation on the IBM 704 John McCarthy published “Recursive functions of symbolic expressions and their computation by machine” in Communications of the Association for Computing Machinery in 1960. CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

History of Lisp (continued) 1970s: advanced dialects -- MacLisp, InterLisp; Lisp machines (Symbolics, Inc.; Lisp Machines, Inc.; Xerox; Texas Instruments) Late 1970s: Scheme, Portable Standard Lisp, XLISP. 1984. Common Lisp. Use of Lisp as internal scripting languages: Gnu Emacs, AutoCAD. 1987 CLOS = Common Lisp Object System. 1994 ANSI Standard Lisp. CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp Interacting with Lisp Interaction takes place in a Lisp Listener Window. Lisp runs an endless loop for interacting with the user: READ EVAL PRINT CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

Interacting with Lisp (continued) > (+ 3 5) 8 > (* 2.5 (+ 2 2)) 10.0 > (setq x 5) 5 > (sqrt x) 2.236068 > (* x x) 25 CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp Defining a function > (* 5 5 5) 125 > (defun cube (n) (* n n n)) CUBE > (cube 2) 8 > (cube 15.001) 3375.6753 CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp Symbolic Values Symbols are like identifiers, but they are commonly used as values as well as variables. > (setq x ’pizza) PIZZA > x > (setq pizza ’pepperoni) PEPPERONI > pizza > (eval x) CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

More on Evaluation of Symbols > (setq x ’y) Y > (setq y ’z) Z > (setq z ’x) X > x > (eval x) > (eval (eval x)) CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp

CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp Values of Symbols A symbol without a value in the current context is said to be “unbound”. The value of a symbol can be any Lisp object, including a number, another symbol, a functional object, a list, and array, etc. A symbol can have several local (“lexical”) values and one global value. However, symbols belong to “packages”, and two different packages can have symbols with the same name. CSE 415 -- (c) S. Tanimoto, 2002 Introducing Lisp