LISP is a computer language that is unique in that it is based on an algebraic structure, the lambda calculus, from pure mathematics. In its purest form, [1] there is no distinction between data and programming code, [2] LISP exists within itself in the form of the eval function, [3] the use of typing on data is optional and necessary only for very large programs, [4] it is not intended to be procedural, the function definitions of a LISP program could be shuffled before being entered into the machine and they would execute just as well, [5] assignment statements do not play a major role in LISP computations -- function definitions are commonly used assignments. [6] memory is managed in terms of linked structures and garbage collection, [7] LISP is interpreted and so programs can be developed and debugged in an extremely modular form -- line-by-line, [8] LISP programs easily interact with the host computer’s operating system and other programs, [9] the syntax for LISP is extremely simple and memorable, and [10] procedures from other languages can be incorperated into a copy of LISP. The purest form of LISP is SCHEME, industrial strength LISP is Common LISP [e.g., Gnu’s Austin/Kyoto Common LISP].
A consequence of these properties is that programs can be written for computations which seem almost magical. Programs can be made to alter, or eventually erase, themselves while executing their intended computation. Self-reproducing programs are short and easy. A single FIXED-POINT program can be written which, when given appropriate functions as arguments, performs a sort, a Newton Search, or writes a recursive program. Further, it is easy to rebuild LISP within itself into a call-by-name evaluator which avoids becomming entangled in unnecessary infinite computations. So, LISP programming is entertaining from a mathematical or computation-theoretic point of view. LISP is usually associated with artificial intelligence. But it goes beyond exotic tricks and a.i. to industrial-strength computing.
That being said, this site will focus on exotica.
