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Lisp is a programming language originally created by John McCarthy in 1958. Despite its age, it is still a popular choice for modern programmers. Lisp has proven itself flexible enough to evolve to meet the needs of modern programmers. Modern implementations often come "batteries-included", meaning that the programmer has access to powerful libraries for databases, regular expressions, networking, and more.

Lisp comes in different dialects, which are divided into different implementations. Three important dialects are Common Lisp, Emacs Lisp, and Scheme.

Important Concepts




In most Lisps and functional languages Lambda is the constructor of unnamed or anonymous procedures and functions.

(lambda (x)
  (* 2 x))

Its use by itself can be observed as such:

> ((lambda (x) (* 2 x)) 5)

In this example the anonymous procedure, or Lambda form, multiplies its argument by 2, its use in a more typical scenario can be observed below via MAPCAR, which applies the unnamed procedure to each of the elements of a list, and returns a list of the results:

> (mapcar (lambda (x)
            (* 2 x))
          '(1 2 3 4 5 6 7 8 9 10))
(2 4 6 8 10 12 14 16 18 20)

Higher Order Procedures


Natural Recursion

Proper Tail Recursion



Compile-time Macros

Read Macros





Common Lisp

Common Lisp was designed by Scott Fahlman, Richard P. Gabriel, David Moon, Guy L. Steele, and Dan Weinreb, and is described in CLTL2, as well as the Common Lisp Hyperspec.

Popular implementations include Allegro Common Lisp, Steel Bank Common Lisp, GNU Clisp, ClozureCL, ECL, and LispWorks.

Emacs Lisp

Emacs Lisp (Elisp) is used to program and extend Emacs. Programmers who either use or are interested in using Emacs should learn Elisp.

A very good tutorial, as well as primary langugage documentation for Elisp is available from directly within Emacs. The introduction can by found by pressing C-h i then typing mEmacs Lisp Intro and pressing Return, and the language documentation can be found by typing mElisp instead. (the "m" tells Info that you are looking for a menu entry, and the rest is the title)


Scheme, created by Guy L. Steele and Gerald Jay Sussman, is the dialect used in SICP.

Two of the most popular implementations are Chicken and GNU Guile, both of which are embeddable, and include a well-designed C API, and an FFI for interfacing with C libraries.

Niche Lisps

System scripting
  • LUSH
  • newLISP
  • Picolisp
  • scsh
  • Harlan
Programming language research