AutoLISP

AutoLISP is a dialect of Lisp programming language built specifically for use with the full version of AutoCAD and its derivatives, which include AutoCAD Map 3D, AutoCAD Architecture and AutoCAD Mechanical. Neither the application programming interface nor the interpreter to execute AutoLISP code are included in the AutoCAD LT product line.

Features

AutoLISP is a small, dynamically scoped LISP (list processing language). It lacks modern LISP features such as a macro system, settable list structure or let bindings. Aside from the core language, most of the primitive functions are for geometry or the manipulation of graphical entities in AutoCAD. The properties of these graphical entities are revealed to AutoLISP as association lists in which AutoCAD "group codes" are paired with values that indicate properties such as points, radii, colors, layers, linetypes, etc. AutoCAD loads AutoLISP code from .LSP files.

AutoLISP code can interact with the user through primitive functions that allow the user to input points, selection sets, numbers and other data. AutoLisp also has a built in GUI mini-language, the Dialog Control Language, for creating interactive forms within AutoCAD.

; example of macro without command-line interface exposed
 
(defun hello_world ()
  (alert "Hello World!"))
 
; example of macro with command-line interface hidden
 
(defun c:hello_world ()
  (alert "Hello World!")
  (princ))
 
; example of LISP's flexible condition handling
 
(cond
  ((= a b) (princ "\n(a) and (b) are equal"))
  ((and (= (type a) 'INT) (= (type b) 'INT)) 
    (princ (strcat "\n(a)+(b)=" (itoa (+ a b)))))
  ((and (= (type a) 'STR) (= (type b) 'STR))
    (princ (strcat "\n(a)+(b)=" a b)))
  ((and (listp a) (= (type b) 'SUBR))
    (mapcar '(lambda (x) (princ (b x))) a)))

History

AutoLISP was derived from a very early version of XLISP, which was created by David Betz. The language was introduced in AutoCAD Version 2.18 in January 1986, and continued to be enhanced in successive releases up to Release 13 in February 1995. After that, its development was neglected by Autodesk in favor of more fashionable development environments like VBA, .NET and ObjectARX. However, it has remained AutoCAD's primary user customization language.

Visual-LISP, a considerably enhanced version of AutoLISP including an IDE, debugger, and compiler, was developed and sold by third party developer Basis Software. Vital LISP was a superset of the existing AutoLISP language that added VBA-like access to the AutoCAD object model, reactors (event handling for AutoCAD objects), general ActiveX support, and some other general Lisp functions. Autodesk purchased this, renamed it Visual LISP, and briefly sold it as an add-on to AutoCAD 14 released in May 1997. It was incorporated into AutoCAD 2000 released in March 1999, as a replacement for AutoLISP. Since then Autodesk has chosen to halt major enhancements to Visual LISP in favor of focusing more effort on VBA and .NET and C++.

AutoLISP has such a strong following that other CAD application vendors added it to their own products. FelixCAD, Bricscad, IntelliCAD and others have AutoLISP functionality, so that AutoLISP users can consider using them as an alternative to AutoCAD. Most development involving AutoLISP since AutoCAD 2000 is actually performed within Visual LISP since the original AutoLISP engine was replaced with the Visual LISP engine. There are thousands of utilities and applications that have been developed using AutoLISP or Visual LISP (distributed as LSP, FAS and VLX files).

External links

• Visual LISP
• The Visual LISP Developers Bible
• AutoCAD History
• AutoLISP FAQ
• AutoLISP Tutorial