Lisp

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Lisp (LISt Processing language) was first developed in the late 1950s at the MIT for research in artificial intelligence. Dozens of Lisp implementations have been built over the years, each with its own idiosyncrasies:

• Maclisp: Many of Lisp implementations were inspired by Maclisp, which was written in the 1960s at MIT's Project MAC.


• Common Lisp: Eventually the implementors of the descendants of Maclisp came together and developed a standard for Lisp systems, called Common Lisp.


• Scheme: In the meantime, Gerry Sussman and Guy Steele at MIT developed a simplified but very powerful dialect of Lisp, called Scheme.


• GNU Emacs Lisp: Most of the GNU Emacs text editor is written in the programming language called Emacs Lisp, which is more than a mere “extension language;” it is a full computer language in its own right.

Lisp is a functional language in which an operation (function name) is written, followed by its arguments, inside parentheses, e.g. (+ x 3).

• LISP is the premier language for artificial intelligence applications.


• Lisp is a dynamic language: editing changes take effect immediately, without the need for recompilation.


• Lisp is primarily a functional language: all work can be done via function composition and recursion.

There is no “main program:” the programmer can call any function from the input prompt. When you learn LISP, you will grasp the essential nature of the language better if you first learn to write programs using only function composition and recursion. This approach is harder, of course, because it requires you to master a new way of thinking.