This repo contains the source codes in Part 1-3 (Lisp: Functions, Recursion, and Lists) of Concepts in Programming Languages By John C. Mitchell.
Plus:
- an internal representation of lisp
- a minimal cheat sheet of pure lisp commands
You can find the source codes in the codes directory.
- On Ubuntu/Debian:
sudo apt install clisp - On Mac:
brew install clisp - On Windows: Download
Lisp lists are represented internally using a tree-like structure of nodes. Each node has two pointers, a left pointer and a right pointer. The left pointer points to a list element (which can be either an atom or another list) and the right pointer points to the remainder of the list.
Form in Lisp:
A Lisp object that is intended to be evaluated is called a form (or an expression).
You can execute functions in lisp using this syntax:
(function_name_or_operator arg1 arg2 ...)| Function/Operator | Description | Example | Output | Output Type |
|---|---|---|---|---|
| cons | create a new Cons Cell | - | - | - |
| ➜ | (cons atom list) | (cons 1 '(2)) | (1 2) | List |
| ➜ | (cons list atom) | (cons '(2) 5) | ((2) . 5) | Cons Cell |
| ➜ | (cons atom atom) | (cons 1 2) | (1 . 2) | Cons Cell |
| ➜ | (cons list list) | (cons '(1 2) '(3)) | ((1 2) 3) | List |
| car | returns first element of the list | (car '(1 2)) | 1 | Atom |
| cdr | returns everything after first element of list as a list | (cdr '(1 2)) | (2) | List |
| eq | returns T if equal else NIL | (eq 2 2) | T | Atom |
| equal/eql/equalp | Read here | - | - | - |
| cond | condition | (cond (cond1 (exp)) (cond2 (exp)) ... (T (last))) | - | - |
| lambda | Read here | - | - | - |
| funcall/apply | Read here | - | - | - |
| quote | Create a list | (quote(1 2 3)) or '(1 2 3) | (1 2 3) | List |
| eval | expects a form to be evaluated and executed as argument. | (eval '(+ 1 2)) | 3 | depends on form |
| defun | define function | - | - | - |
| "+ - * / mod" | mathematic operators | (+ 1 2) | 3 | Atom |
| "< > = <= >=" | boolean operators | (< 2 5) | T | Atom |
| rplaca | replaces the car of the cons with object | (rplaca '(1 2) 5) | (5 2) | - |
| rplacd | replaces the cdr of the cons with object | - | - | - |
| ➜ | (rplacd list atom) | (rplacd '(1 2) 5) | (1 . 5) | Cons Cell |
| ➜ | (rplacd list list) | (rplacd '(1 2) '(4 5)) | (1 4 5) | List |