Chapter 19: Visual Lisp
After completing this Chapter, you will be able to do the following:
•
What is AutoLISP
•
Launching Visual LISP
•
Terminology and Fundamental Concepts
What is AutoLISP?
AutoLISP is based on the LISP programming language, which is simple
to learn and very powerful.
AutoCAD has a built-in LISP interpreter that lets you enter AutoLISP
code on the command line or to load AutoLISP code from external files.
AutoLISP applications are stored in ASCII text files with the .lsp
extension. These files generally have a header portion that describes a
routine, itsuse, and any specific instructions. This header might also
include comments that document the author and the legal information
regarding the use of the routine. You can view and edit these files with a
text editor or word processor that can produce an ASCII text file.
Invoke the APPLOAD command or the AutoLISP load function to
load an application. Loading an AutoLISP application loads the
AutoLISP code from the LSP file into system's memory.
By default, the acad.lsp loads only once, when AutoCAD starts, while
acaddoc.lsp loads with each individual drawing. This lets you
associate the loading of the acad.lsp file with application startup, and
the acaddoc.lsp file with drawing startup.
The acad.lsp and acaddoc.lsp startup files are not provided with
AutoCAD. It is up to the user to create and maintain these files.
AutoLISP has been enhanced with Visual LISP (VLISP), which
offers an integrated development environment (IDE) that includes a
compiler, debugger, and other development tools to increase
productivity.
VLISP represents the next generation of LISP for AutoCAD. It adds
more capabilities and extends the language to interact with objects
using ActiveX. Visual LISP provides three file format options for
AutoLISP applications :
Reading ASCII AutoLISP file (.lsp) - is an ASCII text file that
contains AutoLISP program code.
Reading an FAS file (.fas) - is a binary, compiled version of a single
LSP program file.
Reading a VLX file (.vlx) - is a compiled set of one or more LSP
and/or DCL files.
Launching Visual LISP
VLISP operates within AutoCAD
Tools menu
Choose AutoLISP > Visual LISP Editor
On-screen prompt
vlisp (ENTER)
Launching Visual LISP
Visual LISP initial window
The Visual LISP window is displayed as a separate window with two
basic child windows:
VLISP console
Trace (by default it’s minimized)
The main areas within the VLISP window are:
Console window - allows you to enter VLISP commands and is
scrollable. You can test VLISP expressions as well as review
previous commands or operations in this window.
Status bar - current conditions related to the operations are
displayed in the bottom left bar of the VLISP window.
Menu bar - menu bar operates like the conventional Windows menu
bar with a brief description of the selected menu item displayed in
the status bar.
Trace window - This window is minimized during startup. It
contains information regarding the VLISP release number and other
startup messages. You will also use this window during debug
operations.
Toolbars - Toolbars allow you to issue commands using the pointand-click method. Instead of navigating the menu bar or
memorizing the command syntax to be entered in the console
window you can select a button to activate the command. There are
five principal toolbar groups: Standard, Tools, Search, Debug, and
View.
Terminology and Fundamental concepts
Lists, operators and arguments, types, parentheses, the
exclamation point, and the concept of the function list comprise
the basis of AutoLISP.
Lists - Practically everything in AutoLISP is a list of one sort or
another. Functions are usually represented as a list of expressions
enclosed in parentheses.
Operators and Arguments - Arguments are those items in a
function list on which the operator operates.
Types - Arguments are classified by their type.
Parentheses - The primary mechanisms for entering and
leaving AutoLISP and entering expressions within AutoLISP
are the open and close parentheses.
Exclamation Point - A leading exclamation point in response
to a prompt is another mechanism for entering AutoLISP. This
tells AutoCAD that the symbol following the exclamation
point is an AutoLISP variable that has been set equal to some
value and that AutoCAD should use the value of the variable
as a response to the prompt.