Definition: LISP

(1) (Locator/Identifier Separation Protocol) A network architecture from Cisco for reducing the size of the constantly expanding routing tables in the Internet. Working in conjunction with the border gateway protocol (BGP), LISP-identified packets enter the core routers with the destination service provider's IP address. The provider's edge routers remove the LISP data and deliver the packets to the end users.

(2) (LISt Processing) A high-level programming language used for developing artificial intelligence (AI) applications. Developed in the late 1950s by John McCarthy, its syntax and structure is very different from traditional programming languages. For example, there is no syntactic difference between data and instructions, which allows the language to be extended in unusual ways by innovative programmers.

LISP is available in both interpreter and compiler versions and can be modified and expanded by the programmer. Many varieties have been developed, including versions that perform calculations efficiently. The following example from the popular Common LISP dialect converts Fahrenheit to Celsius. See LISP machine.

   (defun convert ()
     (format t "Enter Fahrenheit ")
     (let ((fahr (read)))
      (format t "Celsius is <126>D"
        (truncate (*(-fahr 32)
            (/ 5 9))))))