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LISP: the list-based Artificial Intelligence and Simulation language LISP is a high-level procedural programming language commonly used in Artificial Intelligence.


Read–Eval–Print Loop (REPL), also known as an interactive toplevel or language shell, is a simple, interactive computer programming environment that takes single user inputs (i.e. single expressions), evaluates them, and returns the result to the user. Programs written in a REPL environment are executed piecewise. The term is most usually used to refer to programming interfaces similar to the classic Lisp machine interactive environment. Common examples include command-line shells and similar environments for programming languages, and is particularly characteristic of scripting languages.

  1. READ - The read function accepts an expression from the user, and parses it into a data structure in memory. For instance, the user may enter the s-expression (+ 1 2 3), which is parsed into a linked list containing four data elements.
  2. EVAL - The eval function takes this internal data structure and evaluates it. In Lisp, evaluating an s-expression beginning with the name of a function means calling that function on the arguments that make up the rest of the expression. So the function + is called on the arguments 1 2 3, yielding the result 6.
  3. PRINT - The print function takes the result yielded by eval, and prints it out to the user. If it is a complex expression, it may be pretty-printed to make it easier to understand. In this example, though, the number 6 does not need much formatting to print.
  4. LOOP - The development environment then returns to the read state, creating a loop, which terminates when the program is closed.




External Links


  1. On LISP (PDF):

See Also

AI | Prolog