Lisp is a family of programming languages that are based on the lambda calculus and characterized by their use of parentheses for code blocks. Lisp is a powerful language with a simple syntax, making it a popular choice for artificial intelligence, data processing, and web development.
Variables in Lisp are declared using the defvar or setq function. Lisp supports dynamic typing, so you don’t need to specify the type of the variable.
(defvar name "John")
(setq age 30)
(setq pi 3.14)
Functions in Lisp are declared using the defun function followed by the function name and parameters. Lisp supports lambda expressions, which are anonymous functions that can be assigned to variables and passed as arguments to other functions.
(defun greet (name)
(format t "Hello, ~a!" name))
(greet "John")
(setq add (lambda (a b)
(+ a b)))
(print (funcall add 2 3))
Lisp supports do, dotimes, and dolist loops, as well as recursion.
(setq numbers '(1 2 3 4 5))
(dolist (number numbers)
(print number))
(dotimes (i 5)
(print i))
(defun countdown (n)
(when (> n 0)
(print n)
(countdown (- n 1))))
(countdown 5)
Lisp supports if, when, and unless statements, as well as the cond control structure.
(setq age 30)
(if (< age 18)
(print "You are too young to vote.")
(if (< age 21)
(print "You can vote, but not drink.")
(print "You can vote and drink.")))
(setq result (if (>= age 18) "You are an adult" "You are not an adult"))
(print result)
Lisp provides several ways to read and write files. You can use the with-open-file macro to create, read, write, and delete files.
(with-open-file (file "example.txt" :direction :output)
(write-line "Hello, world!" file))
(with-open-file (file "example.txt" :direction :input)
(let ((content (read-line file)))
(print content)))
(delete-file "example.txt")