comp.cad.autocad AutoLISP FAQ

Title: comp.cad.autocad AutoLISP FAQ
Archive-name: CAD/autolisp-faq
Version: 2.28
Last-modified: "2002-06-25 08:43:41"
Posted-By: Reini Urban <>
Posting Frequency: monthly
Copyright: see Appendix [A]

Welcome to the comp.cad.autocad AutoLISP FAQ!

AutoLISP is a scripting language for AutoCAD, a well known CAD package. This AutoLISP FAQ is posted to comp.cad.autocad, alt.cad.autocad and the *.answers groups monthly.
Some AutoCAD FAQ's are at but not posted to comp.cad.autocad.
The contents and the samples apply to all releases of AutoLISP since Release 10, including Visual Lisp, Vital Lisp and ACOMP.
There's no special AutoLISP newsgroup. Best are comp.cad.autocad or autodesk.autocad.customization, but please don't bother comp.lang.lisp!
Source code of all functions in this FAQ is in FAQ-CODE.LSP (for location see [A.1]).
Thanks to all who have contributed. Corrections and contributions to always welcome. Please see AcadWiki:RulesToLiveBy for Netiquette

(| changes, + new in items this posting, intermediate personal comments and uncertainties in <..>)

Table of Contents

part 1: General
[0] The Future of AutoLISP? Should I learn it or VB instead?
[0.1] What changed with AutoCAD 2000?
[0.2] We cannot create ARX anymore?
[1] Where can I find AutoLISP routines on the Internet?
[1.1] Are the comp.cad.autocad articles stored somewhere?
[1.2] Autodesk's SDK
[2] What are the best books to learn AutoLISP?
[2.1] Online AutoLISP documents, Winhelp [deleted]
[2.2] AutoLISP Coding Style
[3] How do I debug AutoLISP programs?
[3.1] Native AutoLISP debuggers
[3.2] Modular style, TRACE
[3.3] BREAK function, debug-print
[4] How can I protect my AutoLISP programs? Security
[4.1] Kelvinate
[4.2] Protect
[4.3] Kelvinate and Protect
[4.4] Convert
[4.5] ACOMP
[4.6] Vital LISP Professional
[4.7] Lisp2C
[4.8] Visual Lisp by Autodesk
[5] AutoLISP compilers
[5.1] ACOMP
[5.2] Vital LISP Professional
[5.3] Visual Lisp by Autodesk
[5.4] Better ones: Common Lisp and Scheme
[6] AutoLISP editors and other tools
[6.1] AutoLISP editors
[6.2] Analyzers, Packager and Parenthesis checkers
[6.3] Pretty Printers
[7] AutoLISP problems and bugs [added]
[8] Sorting with AutoLISP [added]
[9] Recursion
[10] Iteration with MAPCAR,...
[11] My LISPs aren't loading at startup anymore [fixes]
[12] How to AUTOLOAD my programs?
[13] How can I pass a variable number of arguments to a LISP function?
[14] How can I avoid stack overflows? [changes]
[15] (command "ROTATE3D") does not work! Why?
[16] Lisp programs operating over multiple drawings
[17] How to export Visual Lisp functions to AutoLISP/AutoCAD?

part 2: Samples, code
[20] General Helper functions
[20.1] List manipulation
[20.2] string manipulation
[20.3] symbol->string
[20.4] AutoCAD entity access
[21] Sample Lisp Programs:
[21.1] Globally change text, polylines, layer utils, date stamp
[21.2] Plot dialog from within Lisp. Using DDE or ActiveX
[21.3] (entmod) and (entmake) Layers, without (command "_LAYER"...)
[21.4] How to select multiple files in Lisp? (as in FILES - Unlock)
[21.5] Replace multiple blocks
[21.6] (vports), VIEWPORT entity, pixel conversion
[21.7] Select all visible objects: zoom coordinates
[21.8] How to write XYZ data of selected objects to a file?
[22] Block Attributes
[22.1] How to access block attributes?
[22.2] How to MODIFY block attributes? DATESTAMP.LSP
[22.3] How to UPDATE block attributes?
[22.4] How to ENTMAKE a Block Complex Entity in AutoLISP
[23] Polylines
[23.1] How to access polyline VERTICES?
[23.2] How to JOIN multiple lines to polylines?
[23.3] Change WIDTH of multiple polylines?
[23.4] Create a polyline or spline: with ENTMAKE or COMMAND
[23.5] How to calculate the LENGTH of polylines?
[23.6] How to revert the polyline direction?
[23.7] How to get the CENTER of a polyline? [new]
[24] Circle/Arc Geometry: BULGE conversion, some trigonometry
[25] DCL: listboxes with tabs or monotext font
[26] EED Extended Entity Data: Get and Store
[26.1] Select objects on their EED with (ssget "X")
[26.2] Get EED from an object
[27] How to break a command in Lisp?
[27.1] How to do an unlimited number of user prompts?
[28] How to decode ACIS internal geometry with Lisp?
[A] Disclaimer, Notes from the authors
+ [A.1] FAQ Locations
[B] Acknowledgements
[C] Recent Changes

[0] The Future of AutoLISP? Should I learn it or VB instead?

AutoLISP will be definitely supported in future releases. VB was introduced to simplify Office Automation: ACAD <-> Excel/Access

Both languages have advantages and disadvantages. You should have a look at both. VB seems to be more graphical and AutoLISP more logical. The object concept of VBA seems to be easier to learn, but you cannot run commands like in AutoLISP.
The new VBA (>= R14.01) is extremely fast. See also [5.2].

The future of AutoLISP already is Visual Lisp. URL's:,, also [0.1] below.

[0.1] What changed with AutoCAD 2000?

The name :) No, there's much more, but you may call it Release 2000, R15 (though 15 is the version number and not the release number), A2000 or abbrevated A2K.

The new Visual Lisp kernel replaced the old xlisp-based AutoLISP kernel. What problems should you expect with Visual Lisp in R2000? (only the bad news)
At I compiled a white paper. Use the LCA to check your lisps.
The major points are:

[0.2] We cannot create ARX anymore?

With AutoCAD 2000 you cannot do that anymore as with ViLL or VLISP 4. Instead you compile to VLX (Visual Lisp Extension), which has basically the same functionality as the old Visual Lisp/Vital Lisp ARX, with the following differences: You don't need ARX modules anymore. This is a feature, no bug.

[1]Where can I find AutoLISP routines on the Internet?

The big AutoCAD tools sites are:

AutoCAD Plugin Store by
This is the by AutoDESK "officially recommended" tools site.
CADalog - The AutoCAD Shareware Clearinghouse (Mike Clark)
The CAD Depot Formerly known as CADSyst (David Whynot), recently bought by TenLinks.
They are specialized in AutoCAD related software and have a very good AutoLISP collection. Other professional AutoLISP shareware sites post their URL's to the newsgroup too.

Other relevant portal sites are: [new]
TenLinks and the UpFront EZine are the best CAD news services.
Autodesk started the portal site Point A.

Some other sites with AutoLISP collections are:

xarch AutoCAD Info & Tools (Reini Urban) (with search)
CAD Users Webring [new]
CADalyst magazine code (compiled by "Hot Tip Harry" Art Liddle)
Owen Wengerd
Terry Dotson
AcadX [new]
Paul Turvill [new]
Vladimir Nesterovky
Theo L.A. Groenenberg
The CADshack (Jeff Foster)
Lisp Factory (Jay Garnett)
Rakesh Rao - AutoCAD Tech Center

Old or broken links are:

AutoCAD Tech Journal code (Peter Sheerin) [old]
CADENCE magazine code (Peter Sheerin) [old, broken]
UCCB AutoCAD and AutoLISP page (Paul Standing) [broken]
Dr.Lisp Utilities (Alexander Medwedew) [fixed]
McNeel's lisp archive [fixed]
Desi Moreno [broken]
PIRS Online
Henry Francis [broken]
SimTel - Coast To Coast - Archive [fixed, very old]
At were documents from the Autodesk Product Support answering technical questions. (Their FAQ's)
The ASA (Support Assistance, some kind of FAQ) was once at, an improved but slow tool is at

[1.1] Are the comp.cad.autocad articles stored somewhere?

There is no comp.cad.autocad archive or such a thing, but there are some search engines which store news articles. In particular: - The biggest news archive. [new]
Formerly known as
Phoaks - People Helping One Another Know Stuff - Automatic Links Extractor
The Autodesk discussion forums have also a search feature at Some specific older news postings are also stored at

[1.2] Autodesk's SDK

Up to Release 12 a Software Development Kit was available directly at Autodesk. The SDK2 was shipped with the international R12 for free. It included a lot of ADS and AutoLISP source code and libraries.

From R13 on Autodesk provides a special developers network, comparable to Microsoft's, the ADN. The CD's are comparable to the old SDK but are more targeted to ObjectARX developers.
Contact your nearest Autodesk headquarter for becoming a member.

Some LISPs are at

In the US, ADN membership costs $600.00 per year. The CDs don't include any SDK per se, but most of the stuff in the original SDKs is included in one form or another. (Owen)

[2] What are the best books to learn AutoLISP?

AutoLISP to Visual LISP [new]
Kevin Standiford, Autodesk Press, ISBN 0-7668-1517
AutoLISP: Programming for Productivity,
William Kramer, Autodesk Press, ISBN 0-8273-5832-6
Essential AutoLISP,
Roy Harkow, Springer-Verlag, ISBN 0-387-94571-7
AutoLISP in Plain English; A Practical Guide for Non-Programmers,
George O. Head, Ventana Press, ISBN: 1566041406
"Maximizing AutoLISP"
Rusty Gesner, Tony and Mark Middlebrook, Tony Tanzillo.
More at
"AutoLISP Reference Manual"
by Autodesk Press.
Up to R12 there was a separate AutoLISP Reference book. Then AutoLISP became a part of the Customization Guide for R13. From R14 on this guide is compiled as Winhelp.

There are a lot of more AutoLISP books around.

Recommended general LISP books (not AutoLISP!) are:

ANSI Common Lisp, (Common Lisp primer)
Paul Graham, Prentice Hall, ISBN 0-13-370875-6
Structure and Interpretation of Computer Programs, (high-level Scheme)
H.Abelson, GJ. Sussman, J. Sussman, MIT Press, ISBN 0-262-01153-0
"This undoubtedly one of the best general computer books ever written."
LISP, 3rd Edition,
Patrick Henry Winston and Berthold Klaus Paul Horn, Addison-Wesley Publishing Company, ISBN 0-201-08319-1
Looking at LISP,
Tony Hasemer, Addison-Wesley Publishing Company, ISBN 0-201-12080-1

[2.1] Online AutoLISP documents, Winhelp [deleted in the posted version]

R14 ships with the complete manuals converted into Winhelp.

Available AutoLISP Winhelp files come with:

For DOS there exists a memory resident program called LISPHLP.EXE
(activates on Ctrl-RightShift-R, from 1988)

LSPDOC: At is a tool available which automatically creates a Winhelp for LISP files.

[2.2] AutoLISP Coding Style

Most of the samples being published by magazines or at various websites are written badly making the AutoLISP learning process even harder for newbies. LISP is hard to read anyway because of it's briefness and countless parentheses. Everybody is enforced to write clear, readable code. Autodesk's samples are quite well written but sometimes overdone. :)

Automatic pretty printers, or so called beautifiers (see [6.3]) automatically format the code according to the standard.

On the R12 CD-ROM in the SDK2 ACG.DOC or at is an excellent Autodesk documentation about coding, commenting and intentation standards to keep lisp code readable.

The most important points are:

[3] How do I debug AutoLISP programs?

[3.1] There were three native AutoLISP debuggers:

See [5] AutoLISP compilers

[3.2] Modular style, TRACE

The best support you can have for debugging is write your code in a well designed, modular style, pulling out distinct tasks into separate functions and then liberally using nested function calls. This will allow you to use the TRACE function as needed to locate any errors.

[3.3] You may include BREAK functions and debug-print into your source code.


;;; Debugging functions (defun break (s) (if *BREAK* (progn (princ "BREAK>> (stop with <Enter>)\nBREAK>> ")(princ s) (while (/= (setq s (getstring "\nBREAK>> ")) "") (print (eval (read s))))))) ;bugfix from v1.3! (defun dbg-print (s) ;accepts atoms and lists (if *DEBUG* (if (listp s) (MAPCAR 'print s) (print s)))) (defun C:DEBUG () (setq *DEBUG* (not *DEBUG*))) ;switch it on and off (defun C:BREAK () (setq *BREAK* (not *BREAK*))) (defun CONT () (setq *BREAK* nil)) ;continue without any interruption ;;;Example (setq *BREAK* T *DEBUG* T) (defun C:TEST () (foreach x '("1" "1.0" "1e-3") (break "in foreach") ; stops evaluation if *BREAK* is on, you can ; enter x and the value of x is printed ; until you enter Enter (setq x (atof x)) ; this is some code which manipulates x (dbg-print x) ; this prints the new value of x ; if *DEBUG* is on ) ) Command: TEST BREAK>> (stop with <Enter>) BREAK>> in foreach BREAK>> x 1.0 BREAK>> (CONT) ; turn off the break nil BREAK>> <Enter> 1.0 1.0 0.001 You may also turn off the debugging output with BREAK>> (setq *DEBUG* nil) to continue in larger loops.

[4] How can I protect my AutoLISP programs?

"You really have to protect it? If you just want to share routines with your friends, why not give them the code? Your code is protected anyway by copyright, even implictly. Working with others can be a great way to get new ideas and lead to a better application.
Some of the best utilities were improved by my friends or I have improved some of my friends utilities." (Dennis)

[4.1] Kelvinate
with KELV.EXE (on the R12 CD-ROM or at the AutoLISP sites [1]) De-Kelvinate lisp's with any pretty printer. But symbol names (functions and variables) will stay garbled and comments are lost.
[4.2] Protect
with PROTECT.EXE (on the R12 CD-ROM or at the AutoLISP sites [1])
Note that unprotectors exist. Free.
[4.3] Kelvinate and Protect
First kelvinate it to make it unreadable, then protect it. Free.
[4.4] Convert
Shareware Lisp En-/Decryptor by Maciej Lukasiewicz
With Convert encrypted "Protected Lisps" cannot be decrypted by other programs, but by Convert it can.
[4.5] ACOMP
AutoLISP compiler ACOMP.EXE, on the R12 international release or at the AutoLISP sites. Free. More docs about ACOMP are at
See also [5.1] AutoLISP compilers
[4.6] Vital LISP Professional
Say "ViLL". Outdated. See [5.2] AutoLISP compilers
[4.7] Lisp2C
LISP to C converter, for R12/R13/R14 Dos/Win (Watcom, Metaware, MSVC Libs)
You need to own such a C/C++ compiler.
[4.8] Visual Lisp by Autodesk
say "VLISP". The Future. see [5.3]

FAS Security:
There was recently a lengthy discussion about FAS security at both newsgroups. Apparently FAS can be decompiled to readable source code, but this tool is not available on the net yet. Rumors say that MNC files can also be decompiled for years now but this doesn't exist the net either. Linked and dropped FAS/VLX (compiled with Optimized/Internal) is similar to Kelvination. Symbol names, strings and numbers are more insecure than algorithms.

Serious encryption is only done with Vital LISP and its successors. Kelvinating [4.1] makes LISP files unreadable and load faster. Protected [4.2] lisp files can be easily decrypted. With Convert -e$GUARD encrypted AutoLISPs can be unprotected only with Convert.

[5] AutoLISP compilers

There are three AutoLISP compilers, better ones could maybe used in the future. Some Lisp and Scheme platforms already do or will support ActiveX or just a simple FFI.

[5.1] ACOMP
ACOMP was supported up to R12 for the international releases only. It is free. It is free, and doesn't work with R13 nor with domestic R12/Win. It produces *.BI4 files and needs special ACADL.EXP supplied as ACADLC.EXP. See The compiler warnings are more explicit on local symbols than ViLL/VLisp.

[5.2] Vital LISP Professional
by Basis Software Inc. USA. License-free runtime modules for R12/R13/R14 DOS/Windows/NT
Basis doesn't continue developing Vital Lisp anymore. See also [6.1] and [4.6]

[5.3] Visual Lisp by Autodesk
VLISP 4 (for R14), the successor of Vital Lisp, is basically the same as ViLL 3.2. Only the GUI, some function names and the docs changed: vill- => vlisp-, vlx- => vl- prefixes. Some vlax- funcs have more hyphens.
With AutoCAD 2000 VLISP replaced the old AutoLISP engine. See [0.1] VLX files are packaged FAS files with optional DCL resources, used by R14/R15.
R15 FAS/VLX are incompatible with previous releases (FAS2 -> FAS4) because of added language features (seperate namespaces).

[5.4] Better ones: Common Lisp and Scheme
Native ARX exists for Corman Common Lisp (a simple console),
COM support for Allegro Common Lisp 5, Lisp Works for Windows and in the future for GambitC.
Via a FFI ("Foreign Function Interface") almost every lisp or scheme can communicate with AutoCAD.
Little work is done with Corman Lisp and ACL5, currently one commercial product uses ACL5 ("Design++" by Design Power)
See for more.
AutoLISP compilers are bytecode compilers needing a runtime system. AutoCAD 2000 uses VLISP now, so the runtime system is included. You cannot create standalone programs, though ViLL/Vlisp (<= R14) creates a stand-alone ARX. The variables are encrypted.

[6] AutoLISP editors and other tools

[6.1] AutoLISP editors

Visual Lisp by Autodesk
see [5.3]. The best and most recommended tool. With AutoCAD 2000 it is included for free.
Emacs for NT
Huge editor and quite hard to learn but it's written and customizable in elisp, which is very similar to AutoLISP. The mother of all editors. Free, for all platforms. Comes in two flavors, XEmacs or GNU ntemacs.
AutoLisp Mode at

Vital LISP outdated by Visual Lisp. Not available anymore. See [5.2] AutoLISP compilers
LispLink 2000
Commercial AutoLISP Editor with Syntax Highlight, Parenthesis Checking, Project Manager, Dialog Preview, and Support for Visual LISP Functions and FAS Compilation.
CodeMagic [new]
Freeware text editor with AutoLISP syntax highlighting.

Old Stuff:
AutoLISP Editor by Tony Tanzillo.
Visual Lisp by WSSW
Old small Windows Lisp Editor. Version 1.0 was even free. Don't mix it up with Visual Lisp, the new AutoLISP. This is just a small editor. See [1]
ADS editor for DOS R12, can evaluate lisp code from within the editor, free.
See [1]
old commercial DOS IDE, internal pretty printer, protect, unprotect, kelvinator, <availability?>
ALLY 3.0 and CADET
Shareware Lisp Analyzer and Editor.
See [6.2]
free, small dos editor which provides parenthesis highlighting.
At A similar editor is ADE.

General customizable programming editors like MultiEdit Pro 7, WinEdit, E!, TextPad, UltraEdit or PFE are widely used also.
They usually don't provide Lisp syntax checking or pretty printing, but (some even regular expression) multi-file search/replace and customizable syntax highlighting.

[6.2] Analyzers, Packager and Parenthesis checkers

Parenthesis checkers should not be used anymore. Editors should do the job. Analyzers generate a function cross-reference, the calling and the reverse callers tree. Packagers are used to generate libraries from various source files, copying all the needed functions. There's currently no code-walker which can internationalize command strings, but with R15 came a lisp analyzer (LCA).
VLISP's [5.3] compiler analyzes (compile with full messages) and checks parens (Ctrl-Alt-C).
Reini's AutoLISP Packager Browsable function cross-referencer, reverse calling tree, creates a library from source files. ("Packager" or "Function Shaker")
PEI's Findvars
Similar to the Packager above, but not only functions, additonally detects symbols to be localized.
I personally use this and my Packager.
RapidLisp v1.0c shareware lisp analyser for R14.
AVC - AutoLISP Variable Collector
Freeware. Finds all variables to be declared per function.
LCA - Autodesk's AutoLISP Compatibility Analyzer [new]
On the Migration CD. Details AutoCAD 2000 compatibility issues found in specified AutoLISP (LSP) or Menu LISP (MNL) files.

ALLY30.ZIP (old)
Shareware LISP analyzer. Checks syntax and prints statistics (function dependence tree), at [1] (old)
LCK LISP Checker 2.1b (graphical) (old)
There are also some AutoLISP programs which count parenthesis.

[6.3] Pretty Printers

Lisp, DCL and FRM source code formatter
Autodesk's source code beautifier.
In the SDK2 or at [1]. Has problems with longer strings, and new-style in-line comments.
in the SDK2 or at [1]
Visual Lisp, Vital LISP, Emacs and Codekey provide internal beautifiers as I'm aware of it.

[7] AutoLISP problems and bugs

For AutoCAD 2000 and unexperienced VLISP users see [0.1]. There are almost no known serious AutoLISP bugs. The language interpreter itself (ACADL.EXE/.EXP, VLISP) works undoubtedly well. Some restrictions are based on the AutoCAD, ActiveX or the Proteus (DCL) engine. Some support LISP programs (i.e. DDMODIFY.LSP) are faulty sometimes. For Visual Lisp see the README.txt which lists all known bugs and limitations. Crashes with reactors are acad bugs.

Two inofficial buglists are at: (the big one) (a private and shorter one)

+ LDATA by Tom Berger (VLISP for R14 and A2000)
In short: Don't use LDATA at all. It may destroy DXF and DWG's in A2000. It is also VERY hard to get rid of them.
List Arguments with DOTTED PAIRS passed from AutoLISP to Visual LISP or back may loose the outer parens.
See the Visual Lisp README (undocumented in Vital Lisp)

SINGLE ATOM LISTS returned incorrectly from EXTERNAL APPS
Visual LISP can not distinguish between a LIST of a single atom (element), and a single atom returned from an external ObjectARX or ADS application.

ENTGET used with LWPOLYLINE, HATCH (R14 only)
The Z coordinate (caddr (getval 10 ele)) is a random number and often causes a floating point exception because it may too low or too high.
Workaround: see part 2, Subject [23.1]

ENTMAKE VERTEX by Terry Dotson (R14 only)
A problem can occur during the process of using (entmake) to create polylines, you must assign the layer to each of the VERTEX definitions (which Autodesk has told us), but you must also assign the layer to the ending SEQEND. Absence of this will cause the SEQEND to end up on the current layer, which can be later frozen. Attempts to move this piece of geometry will then cause a EREGEN error and crash in R14 (only).

ACAD_STRLSORT: Strange sort order in Windows.
The chars in Windows are not sorted on its ASCII representation! Instead according the actual codepage, (getvar "SYSCODEPAGE") which is different.

Windows: (acad_strlsort '("-1" "+1")) -> ("-1" "+1"), DOS: (acad_strlsort '("-1" "+1")) -> ("+1" "-1") Both: (mapcar 'ascii ("-" "+")) -> (45 43) More at

(ai_propchk) was renamed to (C:AI_PROP) in the R13c3 update patch.
"The AutoLISP function ai_propchk has been changed to c:ai_prop so that it behaves similarly to other commands. This allows pressing return to bring back DDMODIFY if selected from toolbar."

Faulty action callbacks in R13 DCL code crash AutoCAD
There is a bug in R13 where AutoCAD crashes with a Fatal Error if an error occurs in AutoLISP code during an action callback from a scroll bar in a dialog box. For instance, if you try to evaluate a null function during the callback, AutoCAD crashes instantly. Technically, this isn't a bug in the AutoLISP interpreter, but we would still call it an AutoLISP bug.

You cannot rely on bitvalue 64 in flag 70 in symbol tables anymore since R13, but in all previous releases.

What else? See the unofficial AutoCAD buglist compiled by Steve Johnson for more faulty AutoLISP programs and behaviours, at (esp: 33, 124, 126, 127, 139, 153, 158, 165, 176, 182, 192, 193, 238, 240, 254, 272, 295)

Protected lisp files
In pre-c4 R13 protected LISP files didn't stay protected in memory. In our opinion, this problem needs to be made known to all, so that developers don't inadvertently assume their protected code is safe from prying eyes. This FAQ topic caused a major problem in moderated CompuServe's AutoCAD Forum. But there are good security methods. See [4].

Limited number of open selection sets
They are intermediatly stored in temporary files. Get rid of not needed selection sets with setting the symbols to nil and run (gc), the garbage collector, which actually closes those files then.
The maximal number depends on the operating system, i.e. in DOS of the FILES= value in CONFIG.SYS
R13 improved the number.

Numbers: range, accuracy, numerical precision
Integer numbers are internal long fixnums (signed, 32-bit), but the communication from AutoLISP to AutoCAD accepts only 16-bit short fixnums, in the range -32768 .. +32767, because AutoCAD needs only short fixnums.

Floating point numbers are doubles (64-bit IEEE). All internal AutoLISP and AutoCAD numerical calculations work with this double format, which should be sufficient. At least the first 14 decimal places are exact.

A common problem is the confusion betwen the actual number (exact) and the rounded string representation. The number which is shown on the command-line is always the rounded string which takes care of LUPREC and DIMZIN.

However with geometric comparisons there often occur unwanted round off errors, so that it's wise to compare points with a small fuzz factor [1e-12 - 1e-6]. (equal pt1 pt2 1e-6) ; 0.000001 rounding error tolerance instead of (equal pt1 pt2), esp. with angles.

VB: It was also reported lately, that with certain automation controllers loaded, numerical accuracy and locale issues (`, vs `.) had undesirable sideeffects. A solution and explanation of this problem is pending. (Mostly in `, as decimal delimiter countries such as Germany)

ACOMP's (EQ) strictness
With [5.1] ACOMP's compiled code you have to take care that the (EQ) behaviour in BI4's is much stricter than in plain AutoLISP. In AutoLISP (eq "1" "1") is T where in acomp compiled code it's nil

The following are not real bugs, that make AutoLISP crash or return false results. They are just bad language implementations.

AND and OR should return the value of the not-NIL argument instead of T. See

MAX and MIN should handle string types too, because < and > accept and process strings too.


For stack overflow errors see [14]

[8] Sorting with AutoLISP

In short: use VL-SORT (generic) or ACAD_STRLSORT (strings only).
but beware: VL-SORT removes duplicate entries (which are EQ)!

I've set up a sort overview at

In LISP mostly used sort method is merge sort (also used in (str-sort) in AutoDesk's TABLES.LSP sample) because that's a natural method for linked lists. Normally (e.g. in C) you use heap sort (for any data) or qsort (for random data) and insertion sort for the small lists (< 7) or sublists within the algorithm.

There is lisp code for shell-sort, bubble-sort, insertion-sort, quick-sort available for any data, lists of lists and indeces to lists. In lisp you can pass the predicate function to sort which is evaluated at run-time. (here called "method"). That's why you need only one sort function for multiple data types (i.e. numbers, points on x or y, strings, ...)

(sort data method) ;method: less-than-predicate ;default for numbers: '< Some sample timings from sorting 100 elements: bubble sort : 13.639008 sec/ 30.08% insertion sort: 13.368042 sec/ 29.48% (fast for sorted lists) shell sort : 13.478973 sec/ 29.73% (poor implementation) merge sort : 2.232971 sec/ 4.92% quick sort : 2.433960 sec/ 5.37% vlx-sort : 0.099976 sec/ 0.22% (Vital LISP internal) acad_strlsort : 0.089996 sec/ 0.20% (AutoLISP's internal, just strings) Pending are timings for vl-sort, vl-isort, STDLIB std-fast-sort, std-sort, std-stable-sort and Vladimir's new merge-sort

[9] Recursion

This is not a often asked question but a very interesting one, because LISP itself is defined recursively and it's a the easiest way to articulate hard problems.

There some fine documents about recursion at especially the Tutorial by Dennis Shinn.

It explains in great detail

(defun FACT (n) (cond ((zerop n) 1) (T (* n (fact (1- n))))))

Note: There's also a self-modifying example of this function explained at

[10] Iteration with MAPCAR,...

Same as with recursion this is not a often asked question, but it's quite hard to understand too.
Iterative statements in AutoLISP are: WHILE, REPEAT, FOREACH and MAPCAR. We use them widely in this FAQ code because they allow brief code.

There's a short course in LAMBDA, QUOTE, MAPCAR... by Vladimir Nesterowsky:

>> "There are 14 paths and 12 pigs. >> How can there be 24 ducks?" >> Is there a lisp command that will allow me to pick these >> lines of text, and recognize the number(s) in each line, >> in order to, say, raise each number by two? >> Leaving the sentence structure, etc, intact? This is one way. (I am sure there are many other ways) (defun MULT2 (strng) ; by Vladimir Nesterowsky (strlgather (mapcar '(lambda (s / n) (if (zerop (setq n (atof s))) s (rtos (* n 2)))) (strlparse strng " ")) ; parse by spaces " ")) ; gather back with spaces

is explained at

;;; flip rows and columns in a matrix (defun TRANSPOSE (l) ; by Doug Wilson (apply 'mapcar (cons 'list l)))

is explained at

[11] My LISPs aren't loaded at startup anymore

LISP files can be loaded at the startup using LOAD in ACAD.LSP. Some LISPs, required with a menu to work, should be loaded from the corresponding <menu>.MNL file. The <menu>.MNL file - if different - should load ACAD.MNL

LISP functions calling commands at the startup should be defined in S::STARTUP of ACAD.LSP. This function is called at the startup after the initialization automatically. Otherwise you'll get the "Command list interruption (6 . 2)" errors.
Note: (command) may be safely called from within MNL files. (S::STARTUP) is mainly used to check for partial menus now.

If the file name was provided without an extension, the LOAD function assumes .LSP. If - without a path prefix, the usual AutoCAD library path is used, which is, exactly in this order,

  1. ) The current directory
  2. ) The directory containing the current drawing file
  3. ) The directories defined in the ACAD environment variable (setup in the Preferences box, SUPPORT paths)
  4. ) The acad.exe directory
If your program isn't loaded anymore automatically, check your AutoCAD library path settings.

With ACADLC (of ACOMP) and the domestic release of AutoCAD R12 ACAD.LSP is not loaded automatically. Therefore you must append (load "ACAD" -1) to your ACAD.MNL.

Sample ACAD.LSP:

;;;ACAD.LSP ;;; Fred the Beaver, 12/12/94 (load "init" -1) ; this loads some tools of mine (defun S::STARTUP () (load "new-end" -1) ; this redefines the END command )

The -1 argument provides LOAD from interrupting the startup process, if any LOAD failure (causing an AutoLISP error). If a failure at load-time occurs, -1 is returned, but the evaluation does not stop. -1 can be any expression as well.

Sample code to enhance S::STARTUP in your code. With VILL/VLISP compiled code this will not work, it must be defined with DEFUN-Q instead.

Functions are generally no lists anymore! Better than to use DEFUN-Q for S::STARTUP is to check for known hooks, a list of user-defined functions which are inserted and evaluated at run-time.

(defun MY::STARTUP () ;your startup code goes here ;.. (princ) ) (setq S::STARTUP (if (and S::STARTUP (listp S::STARTUP)) ;already defined in ACAD.LSP ; or elsewhere (append S::STARTUP (cdr MY::STARTUP)) ;append your code MY:STARTUP)) ;just your code

or a simple one:

(if (and S::STARTUP (listp S::STARTUP)) (setq S::STARTUP (append S::STARTUP (list func '(princ)))) (setq S::STARTUP (list nil func '(princ)))) Vladimir Nesterovsky:

The main difference now in A2K+ versions is that functions defined with DEFUN are now a new datatype, USUBRs, and not lists as before. But when the function is defined with DEFUN-Q, it is a list still, like in previous versions.

Here's the utility function to use that works in both cases:

 (defun plug-into-startup (funcname) ;by VladimirNesterovsky
   "to be called with quoted function name"
   (eval (list
     'defun 's::startup ()
     (if s::startup (list (list 'quote s::startup)))
     (list funcname))))

so if you have all your startup code packed into one routine

 (defun my-startup ()
   (alert "My Startup"))

you make it work with the call

 (plug-into-startup 'my-startup)

inside your code that is executed on startup, e.g. acaddoc.lsp or whatever.

See also [12] How to AUTOLOAD my programs?

[12] How to AUTOLOAD my programs?

How to load my programs automatically?
You can either load your whole program at startup (see [11] My Lisp doesn't load at startup anymore) which needs more time and memory at startup time, or you can define them via the autoloading mechanism.
From R14 on ARX programs use a new autoloading scheme (called "demand loading") with some registry settings and not from ACADRxx.LSP anymore.

Look at the end of your ACADRxx.LSP how AutoCAD autoloads its programs.

;;;===== AutoLoad LISP Applications ===== ... (autoload "dline" '("dline" "dl")) ...

This defines the commands DLINE and DL in the list to be loaded from the file DLINE.LSP when the user first calls the command DLINE or DL. Before that the function is simply defined like this one:

(defun C:DL () (load "DLINE")(C:DL))

In fact the definition is more complicated because of error handling: Ctrl-C, loading errors, wrong file or path.

After the first call the function is overwritten with the definition in the program.

Advantages of autoloading:
Startup is faster, because you dont have to load all your lisp files. You just define the simple wrapper definition as above. This is done by the (autoload) function

You need less memory

On errors in your program you will fall into a never ending loop, which will only stop after a stack overflow or Ctrl-C
Note: with acomp compiled code even Ctrl-C is impossible, insert a call to an uncompiled (princ) somewhere.

You have to define and maintain all command names from your program in the autoloader definition. Changes to the lisp filename or the command name will cause the above error.

Where to put your (autoload) definitions?
Not to ACADR14.LSP. Well we recommend putting it to an initialization file of yours and not to ACAD.LSP because this is often changed by different applications and ACAD.LSP should be kept rather small.

I.e. put it to a AUTOLOAD.LSP or INIT.LSP, which is loaded from ACAD.LSP See [11] My Lisp doesn't load at startup anymore

It should be mentioned that users should *not* modify ACADRxx.LSP. Since ACAD.LSP is not overwritten during upgrades, it is guaranteed to remain safe. In addition (as we saw with the R13c4a patch) if the ACADR13.LSP file has been modified, then the patch process may refuse to update it, thus resulting in program malfunctions.

[13] How can I pass a variable number of arguments to a lisp function?

With pure AutoLISP this is not possible.

You can either pass all your arguments in a list like this:

;;; print a variable number of arguments (of any type) (defun MY-PRINC (x) ;; simple version, for better stuff look at the SDK2: PRINTF.LLB (if (listp x) (mapcar 'princ x) (princ x)))

Or you have to define the function in ADS or ARX and export it to AutoLISP. Then you are free to write:

(ads-print "Hello " "World " 1 2 3) or even (ads-printf "Hello %s %i %i" "World" 2 3)

Look at Reini Urban's and Vladimir Nesterovsky's ADS samples at for implementations of the above examples.

Official wishes were pointed to AutoDesk regarding &optional as AutoLISP language enhancement, but it was not implemented so far.

[14] How can I avoid stack overflows?

In old AutoLISP the stack size was hardcoded. It couldn't be extended, but its size should be sufficient for most purposes. In the Visual Lisp IDE the stack overflow is simulated at 984 recursions, on the A2000 commandline or loaded programs outside the IDE there's no overflow anymore. This is dangerous on recursion errors of yours, see [9]. Most stack overflow errors occur on a program error of yours, preventing the system from falling into an endless loop, or from using recursive functions on large lists. Therefore you are limited to quite short lists with recursive functions and old versions.

You cannot decrease your used stack size with using less local parameters in your recursive function. However do not use APPLY, EVAL or MAPCAR to call your function recursively, because they eat up the stack. Using tail recursion doesn't help either. You have to convert your recursive function to a iterative one. (There is a mathematical theorem that says, that every recursive function can be converted to a iterative one, tail-recursive ones even automatically.) Iterative versions may use stack-like functions like (push) and (pop), but those versions store the stack on the heap (AutoLISP node space), which size is only limited by your amount of virtual memory available.

You can test the stack overflow with this simple function:

;;; create a list of n numbers (zero based) (defun INTLST (l n) (cond ((zerop n) l) (T (intlst (cons (1- n) l) (1- n))))) and try: (setq n 100)(while (intlst nil (setq n (+ 10 n)))(print n)) In AutoLISP of R12/DOS you reach the stack limit with (intlst nil 138), in A13/Win with (intlst nil 240), in acomp bi4's with (intlst nil 1240), in Vital LISP IDE with (intlst nil 984). With R10c10, the first dos extended lisp version, you could enhance the lisp stack size with the environment variable LISPSTACK. acomp for R10 had COMPSTACK. With Vital LISP or Visual LISP RTS or A2000 (outside the IDE) the stack size is unlimited.

Conversion to an iterative version yields the required results:

(defun INTLST (n / l) (repeat n (setq l (cons (setq n (1- n)) l)))) ;this looks ugly but it works

[15] (command "ROTATE3D") does not work! Why?

Some commands are no internal AutoCAD commands, they are simple AutoLISP programs beginning with C: even if they are defined in ADS programs. Only native Rx applications (or now with vlax-add-cmd) export true commands.

A list of all these commands are found in ACADR13.LSP in the AUTOLOAD section. (see also "[12]")
All these commands have to be called with (C:ROTATE3D) instead of (command "ROTATE3D").

However ADS functions may take optional arguments. See the customization manual for more.
i.e. (c:rotate3d ss p1 p2 angle) is also valid, even (rotate3d ...)

[16] LISP programs operating over multiple drawings

"I am having trouble getting a lisp file that will open a drawing and continue running. Once the new drawing is opened the Lisp file ceases to exist in the Autocads memory. It has to be reloaded to recognise the commands."
LISP memory is reloaded on a per drawing basis. There are some ways to execute a LISP on multiple drawings:
  1. via a script that executes on multiple files. MYSCRIPT.SCR. (load "mylisp") _QSAVE _OPEN !nextdwg (load "mylisp") _QSAVE _OPEN !nextdwg ...
  2. External 3rd party software such as RunLisp or DDSCRIPT automate step 1.
  3. R14 has a new feature, called 'Persistent LISP'.
    Set it in Preferences-Compatibility-Persistent Lisp
  4. Vital LISP has a built-in variable to act as Persistent Lisp:
    (setq *VILL-NEW-FULL-INIT* nil) ;keep symbols between sessions VLISP renamed it to *VLISP-NEW-FULL-INIT*

[17] How to export Visual Lisp functions to AutoLISP/AutoCAD?

C: functions are automatically exported to AutoLISP. Plain vlisp/vill lisp functions must be exported either with (vl-acad-defun 'myx-funcname) or their symbols may be exported with a special compiler pragma, defined either in the LSP file or in the GLD (global declarations) file. Better use special prefixes for such functions. .GLD: (AUTOEXPORT-to-ACAD-PREFIX ;| name prefixes for functions to be autoexported to AutoCAD: (strings) |; "myx-*" ) or one by one .LSP: (pragma '((export-to-acad myx-func1 myx-func2))) Note: There may exist known bugs in vlisp and vill with lists of atomic symbols and dotted pair lists in such functions arguments and return values. See [7].

Functions exported by external apps which are used in your application must be defined via XDF.

Symbols (variables) whose values are updated in Visual Lisp and which values are also used in AutoLISP or AutoCAD (the menu e.g.), first may be marked for the compiler to be external with: (pragma '((not-localize myx:symbol)))
but the value must be exported with
(vlisp-export-symbol 'myx:symbol)
each time the value is changed in Visual Lisp and control is returned to AutoCAD to be able to get the latest value in AutoLISP or in AutoCAD with !myx:symbol

In AutoCAD 2000 it is much simplier, however you might need to export your function from the protected namespace then with VL-DOC-SET.
See also

part 2: samples, code

[20] General helper functions

For more general AutoLISP functions please see the AutoLISP Standard Library at Other code is available at some AutoLISP sites [1] or included in the SDK's by Autodesk [1.2]

I included here some very useful helper functions for shorter samples in answers on the net.
You could rely on the fact that these functions are in common knowledge such as the famous dxf function, which is defined as
(defun dxf (grp ele) (cdr (assoc grp ele))) and the specific counterpart of (getval) which works with either an ename or entget list.

[20.1] List manipulation

See also Useful sample functions for list manipulation are: ;;; a not empty list? (defun CONSP (x) (and x (listp x))) ;;; Returns the index of the first element in the list, ;;; base 0, or nil if not found ;;; (position 'x '(a b c)) -> nil, (position 'b '(a b c d)) -> 1 (defun POSITION (x lst / ret) (if (not (zerop (setq ret (length (member x lst))))) (- (length lst) ret))) ;;; Removes an item from a list (double elements allowed) ;;; (remove 0 '(0 1 2 3 0)) -> (1 2 3) (defun REMOVE (ele lst) ; by Serge Volkov (apply 'append (subst nil (list ele) (mapcar 'list lst)))) ;;; Conditional remove from flat list. ;;; fun requires exactly 1 arg ;;; (remove-if 'zerop '(0 1 2 3 0)) -> (1 2 3) ;;; (remove-if 'numberp '(0 (0 1) "")) -> ((0 1) "") (defun REMOVE-IF (fun from) (cond ((atom from) from) ;nil or symbol (return that) ((apply fun (list (car from))) (remove-if fun (cdr from))) (t (cons (car from) (remove-if fun (cdr from)))) ) ) ;;; Keeps all elements to which the predicate applies. ;;; Say: "keep if". It need not be defined recursively, also like this. ;;; [fixed, thanks to Serge Pashkov, in FAQ-CODE.LSP it was okay] (defun REMOVE-IF-NOT (pred lst) ; by Vladimir Nesterowsky (apply 'append (mapcar '(lambda (e) (if (apply pred (list e)) (list e))) lst))) ;;; Conses ele to list if not already in list ;;; trick: accepts quoted lists too such as ;;; (setq l '(1 2 3) (adjoin 0 'l) ;;; -> !l (0 1 2 3) (defun ADJOIN (ele lst / tmp) (if (= (type lst) 'SYM) (setq tmp lst lst (eval tmp))) (setq lst (cond ((member ele lst) lst) (t (cons ele lst)))) (if tmp (set tmp lst) lst) ) ;;; ROT1 - put the first element to the end, simple version ;;; (rotate by one) (defun rot1 (lst) (append (cdr lst) (list (car lst)))) ;;; BUTLAST - the list without the last element (defun butlast (lst) (reverse (cdr (reverse lst))))

[20.2] String manipulation

Please check Some useful string functions would be:
All of them and much more are in the Stdlib (see above). Some are at or in your AI_UTILS.LSP. You'll need them esp. for DCL functions.

[20.3] symbol -> string

The inverse function to (read) would be (symbol-name). The following is the only general way, but there exist better special methods. ;;; SYMBOL-NAME returns the name of a symbol as string ;;; converts any valid lisp expression to its printed representation ;;; (symbol-name a) -> "a", (symbol-name '(0 1 2 a)) -> "(0 1 2 A)" (defun SYMBOL-NAME (sym / f str tmp) (setq tmp "$sym.tmp") ;temp. filename, should be deleted (setq f (open tmp "w"))(princ sym f) (close f) (setq f (open tmp "r") str (read-line f) f (close f)) str ) For plain symbols exists a better trick explained by Christoph Candido at
ViLL/VLISP introduced a fast VL-SYMBOL-NAME. See also

[20.4] AutoCAD entity access [renamed SSAPPLY to SSMAP]

See also ;;; returns the first group value of an entity. ;;; like the wellknown (dxf) function but accepts all kinds of ;;; entity representations (ename, entget list, entsel list) ;;; NOTE: For getting 10 groups in LWPOLYLINE's not usable! (defun GETVAL (grp ele) ;"dxf value" of any ent... (cond ((= (type ele) 'ENAME) ;ENAME (cdr (assoc grp (entget ele)))) ((not ele) nil) ;empty value ((not (listp ele)) nil) ;invalid ele ((= (type (car ele)) 'ENAME) ;entsel-list (cdr (assoc grp (entget (car ele))))) (T (cdr (assoc grp ele))))) ;entget-list ;;; Ex: (gettyp pline) => "POLYLINE" (defun GETTYP (ele) ;return type (getval 0 ele)) ;;; assure ENAME ;;; convert the entity to type ENAME (to write shorter code) (defun ENTITY (ele) ;convert to element name (cond ;accepts the following types: ((= (type ele) 'ENAME) ele) ; ENAME ((not (listp ele)) nil) ; error: no list ((= (type (car ele)) 'ENAME) (car ele)) ; entsel-list ((cdr (assoc -1 ele))) ; entget-list or nil ) ) ;and now just: (defun getval (grp ele) (cdr (assoc grp (entget (entity ele))))) ;;; Ex: (istypep ele "TEXT") ;;; is element a "SOLID"? (defun istypep (ele typ) ;check type (= (gettyp ele) typ)) ;;; Ex: (istypep ele '("TEXT" "ATTDEF")) ;;; is element a "TEXT" or a "ATTDEF"? (defun ISTYPEP (ele typ) ;better implementation to accept lists too (cond ((listp typ) (member (gettyp ele) typ)) ;fixed ((stringp typ) (= (gettyp ele) typ)) ;assume typ uppercase, wcmatch (T nil))) ; would be nice but slower ;;; Ex: (getpt (entsel)) => ( 0.1 10.0 24) (defun GETPT (ele) ;return the startpoint of any element (getval 10 ele)) ;group 10 ;;; Ex: (getflag pline) => 1 if closed (defun GETFLAG (ele) (getval 70 ele)) ;same with the entity flag ;;; bitvalue val in flag of element set? ;;; Ex: (flagsetp 1 pline) => T if closed ;;; Ex: (flagsetp 16 vertex) => T if spline control point (defun FLAGSETP (val ele) (bitsetp val (getflag ele))) ;;; Ex: (bitsetp 4 12) => T ;bitvalue 4 (=2.Bit) in 12 (=4+8) is set (defun BITSETP (val flag) (= (logand val flag) val)) ;;; convert selection set to list. slow, but easy to write. ;;; Note: it's also wise to use ai_ssget, because some ents could be ;;; on locked layers ;;; Ex: (sslist (ai_ssget (ssget))) => list of selected unlocked ents ;;; or (mapcar 'entupd (sslist (ssget "X" '((8 . "TEMP"))))) ;;; - regens all entities on layer TEMP (defun SSLIST (ss / n lst) (if (= 'PICKSET (type ss)) (repeat (setq n (sslength ss)) (setq n (1- n) lst (cons (ssname ss n) lst))))) ;;; Map a function over each entity in ss, in reversed order. ;;; Faster, but not so easy to understand. see [22.2] ;;; [renamed from SSAPPLY to SSMAP to match the stdlib name] ;;; Ex: (ssmap 'entupd (ssget)) ; regenerate only some entities (defun SSMAP (fun ss / n) (if (= 'PICKSET (type ss)) (repeat (setq n (sslength ss)) (apply fun (list (ssname ss (setq n (1- n))))))))

[21] Sample Lisp Programs:

[21.1] Globally change texts, polylines, layer utils, datestamp

For globally changing text attributes use CHTEXT.LSP in your sample directory.

For globally changing polyline attributes, freeze layers by pick and other similar tasks search for free lisp tools at any AutoLISP site. See also [1] and some code at [22], [23], and [24].

For putting a datestamp and others onto your plots automatically first check out if your plotter supports HPGL/2. Then use the internal HPGL/2 driver and configure the datestamp in HPCONFIG.

DATESTAMP.LSP: Change the plot header attributes by yourself as in [22.2]. A professional plotstamp routine is here:

[21.2] Plot dialog from within Lisp. Using DDE or ActiveX

From R14 on use INITDIA
(initdia)(command "_PLOT")

Calling the PLOT dialogbox from AutoLISP before R14 was possible only under Windows i.e. with LISPPLOT by Mike Dickason. This fed the keyboard buffer with keystrokes. or also:
Otherwise create a script and call this at the end of your lisp, but this will not show up the dialogbox.

Xiang Zhu: You can use "ddelisp" under Windows to do something like the following:

;;; [fixed for all releases] (defun DDECMD (str / tmp acadver ddestr) (if (not (boundp 'initiate)) (cond ((= 14 (setq acadver (atoi (getvar "ACADVER")))) (setq ddestr "AutoCAD.R14.DDE") (arxload "ddelisp")) ((= 13 acadver) (setq ddestr "autocad.r13.dde") (xload "ddelisp")) ((= 12 acadver) (setq ddestr "autocad.dde") (xload "ddelisp")) (T (princ "DDE not supported")(exit)))) (if (not (zerop (setq tmp (initiate ddestr "system")))) (progn (execute tmp (strcat "[" str "]")) (terminate tmp) str))) For R12 use "autocad.dde" as the server name. Then, inside your lisp or script, you can do (ddecmd "_plot "). Function DDECMD will return nil if something wrong, or the string you passed if successful. The string is just like what you type under the command prompt from keyboard, so you need put a space or a return, which is "^13" here, to end the string.

Besides, the function is very useful in the following situation: If within a lisp, you need to call an AutoCAD transparent command like LAYER, normally you will use (command "_layer"), but after using this line, the lisp own will not be transparent. Using the function, you will solve this problem.

Beware that Acad accepts only DDE commands if the command line is active, that means no dialogbox must be open.

With VLISP/ViLL ActiveX methods can be used also:

;;; vlisp syntax: (setq vlax:ActiveDocument (vla-get-ActiveDocument (vlax-get-Acad-Object))) (setq plt (vla-get-plot vlax:ActiveDocument)) ;=> plot object (vla-PlotWindow plt pt1 pt2) ; define window (pts in WCS) (vla-PlotPreview plt 1) ; 0 for partial, 1 for full (vla-PlotToDevice plt "Default System Printer") ; if it exists With R14 INITDIA was introduced, which can be applied to most (but not all) dialogs:
(initdia)(command "_PLOT")
With A2000 use OLE (the VLA- methods) instead of DDE.

[21.3] (entmod) and (entmake) Layers, without (command "_LAYER"...)

ENTMOD a layer
I try to change a layer property without calling COMMAND function inside a lisp routine.

Since R13, using the following lisp

(setq tbl_lst (entget (tblobjname "LAYER" "ANY_LAYER")) clr_grp (assoc 62 tbl_lst)) (entmod (subst (cons 62 (- (cdr clr_grp))) clr_grp tbl_lst)) you can toggle "ANY_LAYER" On or Off, even it is the current layer.

But AutoCAD doesn't know a table entry has been changed until you click the Layer Control on the toolbar or something similar. Besides, you can issue 'DDLMODES to see On/OFf property of "ANY_LAYER" changed.
Doing the same way to freeze a layer, you will still see entities on that layer shown on screen, but you can not select them, until you do something related to layer settings, and AutoCAD will hide those entities.

ENTMAKE a layer
You must get your pattern with entget, using the table object name as argument. This table object name can be retrieved with the TBLOBJNAME function: (entget (tblobjname "LAYER" "Any Layer Name")) ; R2000 can have spaces! ;;; This routine will create a layer with any name you type: (defun C:MLAY () ; by Reinaldo Togores <> (setq laynam (getstring "\nLayer name: ")) (entmake (list '(0 . "LAYER") '(5 . "28") '(100 . "AcDbSymbolTableRecord") '(100 . "AcDbLayerTableRecord") (cons 2 laynam) '(70 . 64) '(62 . 7) '(6 . "CONTINUOUS") ) ) )
[21.4] How to select multiple files in Lisp? (as in FILES - Unlock)

[21.5] Replace multiple blocks

A search at the lisp archives yielded those hits:
=> 97code.htm and a question for your username which can be obtained free and automatically
xarch: and search for "BLOCK;REPLACE"
also at the Cadalog: Keyword "Block Replace"
=> (this one is the best)

[21.6] (vports), VIEWPORT entity, pixel conversion
VIEWPORT entity:
The answer to "I can do an (entget) on a VIEWPORT and get its lower left (DXF group 10) and upper right (DXF group 11) corner. But it appears that these coordinates are in the paper space system. What I'm interested in finding out is what portion of the "real" drawing (the model space drawing) are currently shown in that viewport." is at has also some tricks.

How to change viewports in AutoLISP?
with (setvar "CVPORT" vport-id) see

With the following functions you convert pixel<->drawing units:

;;; Conversion pixel to drawing units (defun PIX->UNITS (pix) (* pix (/ (getvar "VIEWSIZE") (cadr (getvar "SCREENSIZE"))))) ;;; Conversion drawing units to pixel (defun UNITS->PIX (units) (* units (/ (cadr (getvar "SCREENSIZE"))(getvar "VIEWSIZE")))) Note also the "Pixel Off by One" Errors in AutoCAD, written by Vibrant

[21.7] Select all visible objects: zoom coordinates
Beware that with (ssget) you will only get visible objects, because all interface functions (entsel,ssget,osnap) work with pixel, only (ssget "X") will select not visible objects. ;;; returns a list of the actual viewport corners in WCS (defun ZOOMPTS ( / ctr h screen ratio size size_2) (setq ctr (xy-of (getvar "VIEWCTR")) ;3D -> 2D h (getvar "VIEWSIZE") ;real screen (getvar "SCREENSIZE") ;2D: Pixel x,y ratio (/ (float (car screen)) ;aspect ratio (cadr screen)) size (list (* h ratio) h) ;screensize in coords size_2 (mapcar '/ size '(2.0 2.0))) (list (mapcar '- ctr size_2) (mapcar '+ ctr size_2))) (defun XY-OF (pt) (list (car pt)(cadr pt))) ;assure 2D coords Note: The points returned from the entity are in WCS but this is OK because the "CP" "WP" and "P" options of ssget expect WCS points ("W" and "C" require UCS points - why the difference I don't know) ;;; one way to define this function (defun SSALL-VISIBLE (/ l) (ssget "C" (car (setq l (maptrans0-1 (zoompts)))) (cadr l))) ;;; or another (defun SSALL-VISIBLE-1 () ;combine "C" and (p1 p2) to one list (apply 'ssget (append '("C") (maptrans0-1 (zoompts))))) ;;; map some pts from WCS to UCS, easier with just one argument [doc fixed] (defun MAPTRANS0-1 (pts)(mapcar '(lambda (pt)(trans pt 0 1)) pts))
[21.8] How to write XYZ data of selected objects to a file?

;;; CDF - comma delimited string (defun cdf-point (pt) (strcat (car pt) ", " (cadr pt) ", " (caddr pt))) ;;; SDF - space delimited, may easier be read back in to AutoCAD (defun sdf-point (pt) (strcat (car pt) " " (cadr pt) " " (caddr pt))) ;;; convert this SDF format back to a point with (defun str->point (s) (eval (read (strcat "(" s ")")))) ;;; Write a XYZ file of all selected objects (SDF see below) (defun C:XYZ (/ ss fname f) (if (and (setq ss (ssget)) (setq fname (getfiled "Write XYZ to file" (strcat (getvar "DWGNAME") ".XYZ") "XYZ" 7)) (setq f (open fname "w"))) (foreach ele (sslist ss) ; -> [20.4] (foreach pt (getpts ele) ; -> [23.1] (write-line (cdf-point pt) f) ) ) ) (if f (close f)) ) ;;; => <fname>.xyz ;;; 0.45, 12.3, -34.0 For a ASC file (SDF-format) simply change all XYZ to ASC and cdf-point to sdf-point above.

For the other way 'round, creating PLINES from a ascii x,y file best convert the file to a script like:

PLINE 300.2,10 350.4,10.4

[22] Block Attributes

[22.1] How to access block attributes?
Check all subentities after the INSERT until the attribute is found. See ;;; returns entget-list of attribute s (STRING) in element ele (ENAME) ;;; or nil if no found (defun ATTELE (ele attname / rslt) (if (and (istypep ele "INSERT") (= (getval 66 ele) 1)) (progn (setq ele (entnext (entity ele))) (while (and ele (istypep ele "ATTRIB")) (if (= (strcase (getval 2 ele)) (strcase attname)) (setq rslt (entget ele) ele nil) ;break the loop (setq ele (entnext ele)) ) ) ) ) rslt ) ;;Example: (attele (entsel) "TEST") ; returns entget-list of ; attribute "TEST" if the block has it BTW: Even trickier functions to get entities DXF group codes are GET and EDLGETENT by Vladimir Nesterowsky. ;;;Sample calls: ;;; return list of 2,1 and -1 group values (defun get-attribs-look-up (block-ename) (get '(2 1 -1) (cdr (edlgetent block-ename)))) (defun all-verticies-and-bulges (pline-ename) (get '(10 42) (cdr (edlgetent pline-ename)))) available at

[22.2] How to MODIFY block attributes? DATESTAMP.LSP
For a very simple DATESTAMP.LSP simply entmod the entget-list of the DATE attribute in your plotstamp block, retrieved from (attele) as above. ;;; change the attribute value to new, group 1 (defun ATTCHG (ele attname new / b) (if (setq b (attele ele attname)) (entmod (subst (cons 1 new) (getval 1 b) b)))) ;;; Change all DATESTAMP attributes in all inserted PLOT* blocks (defun C:DATESTAMP () (ssmap ; fixed and renamed '(lambda (ele) (attchg ele "DATESTAMP" (today)) (entupd ele) ) (ssget "X" '((0 . "INSERT")(2 . "PLOT*"))) )) ;;;return todays date, could be a DIESEL or this string conversion (defun TODAY (/ s) (setq s (rtos (getvar "CDATE") 2)) ;gets the julian date (strcat (substr s 5 2) "-" (substr s 7 2)"-"(substr s 3 2))) Automatic datestamps are normally done with either RTEXT} (bonus/express tools) or HPCONFIG with a HPGL/2 plotter. (<a2000i)
[22.3] How to UPDATE block attributes?
There exists a SUPPORT\ATTREDEF.LSP to update attribute properties (position, layer, ...) for already inserted blocks.

On complex entities you must entupd the header entity, to see the update on the screen (it forces an element REGEN). ;;; Example: (setq s (getstring "Change Attribute to: ")) (attchg (attele (setq b (entsel "of block: ")) s))) (entupd (car b)) ; the block, not the attribute ;;; some more helper funcs to get the main entity of any attribute ;;; or vertex (defun MAIN-ENTITY (ele) (setq b (entity b)) ;force ENAME (while (istypep b '("ATTRIB" "ATTDEF" "VERTEX")) (setq b (entnext b))) ; loop until no more sub-entities (if (istypep b '("SEQEND" "ENDBLK")) (getval -2 b) ;complex entity -> header b ;normal entity ) )

[22.4] How to ENTMAKE a Block Complex Entity in AutoLISP>

There is an example how to use multiple calls to (entmake) to create the block header, the entities, closes the block and finally (entmake) the INSERT. For anonymous blocks beware that only (setq bn (entmake '((0 . "ENDBLK")))) returns the blockname for (entmake (list '(0 . "INSERT")'(70 . 1)(cons 2 bn) ...))

[23] Polylines

Since R14 LWPOLYLINE's store the vertices in one entity as multiple 10 groups! So (assoc) will not work.
[23.1] How to access polyline VERTICES?
A polyline VERTEX is a subentity of a POLYLINE (same as an ATTRIBUTE is a subentity of an INSERT element or a ATTDEF of a BLOCK). Therefore the same functions as in [22.1]-[22.3] can be used. ;;; return only some assoc values in the list (for LWPOLYLINE) (defun group-only (grp lst) (mapcar 'cdr (remove-if-not '(lambda(pair)(= grp (car pair))) lst))) ;;; return the vertex list of a polyline or of any other element (defun GETPTS (ele / pts) (setq ele (entity ele)) ;force type ENAME (cond ((istypep ele "POLYLINE") (while (istypep (setq ele (entnext ele)) "VERTEX") ;; omit fit and spline points (conservative style) (if (not (or (flagsetp 1 ele) (flagsetp 8 ele))) ;bugfix! (setq pts (cons (trans (getpt ele) ele 0) pts))) (reverse pts))) ;; Special case: you have to map it, assoc finds only the first. ;; Fix a LWPOLYLINE bug in R14: internally stored as 2d point, ;; (entget) returns fantasy z-values. ((istypep ele "LWPOLYLINE") (mapcar '(lambda(pt)(trans (list (car pt)(cadr pt) 0.0) ele 0)) (group-only 10 (entget ele)))) ;; insert here possible other types, such as ((istypep ele '("TEXT" "CIRCLE")) (list (getpt ele))) ;; more like this (serge's style). LWPOLYLINE code above. (T (apply 'append (mapcar '(lambda (n / p) (if (setq p (getval n ele)) (list p))) '(10 11 12 13))) ) ;; or like this (conservative style) ;;(T (foreach n '(10 11 12 13) ;; (if (setq p (getval n ele)) (setq pts (cons p pts)))) ;; pts ;;) ) ) Suggestions by Vladimir Nesteroswky for a different vertex structure: See [22.1] (defun vertices-and-bulges( pline-ename ) (mapcar 'cdr (remove-if-not '(lambda(ele) (bitsetp 9 x)) (get '(70 10 42) (cdr (edlgetent pline-ename)) => list of (10 42) pairs of the pline ;;;which can also be written as: (defun flag9p (ele) (flagsetp 9 ele))) ;true if fit or spline point (mapcar '(lambda (ele) (remove-if-not 'flag9p (cdr (edlgetent pline-entname)))) see also [23.5] for a different edge structure (segments) of plines.

[23.2] How to JOIN multiple lines to polylines? [fixed]
Simply try to join each element with all selected, but beware that a entity already joined cannot be entget'ed anymore, because it's deleted. ;;; This sample converts all selected elements to polylines and ;;; tries to join as much as possible. (defun C:JOINPOLY (/ ele ss) (foreach ele (sslist (setq ss (ssget))) ;better process lists (if (entget ele) ;not already joined (cond ;(then it would be nil) ((istypep ele '("ARC" "LINE")) ;; but you should check Z of lines and UCS here too (command "_PEDIT" ele "_y" "_j" ss "" ""); convert and JOIN ) ((and (istypep ele '("POLYLINE" "LWPOLYLINE")) ;fixed (not (flagsetp 1 ele)) ;not closed (< (rem (getflag ele) 128) 8)) ;ignore meshes and such (command "_PEDIT" ele "_j" ss "" "");ucs check omitted for brevity ) ) ) ) )
[23.3] Change WIDTH of multiple polylines
With the help of the above defined helper function it's a short one: (defun C:POLYWID (/ wid ele) (initget 5)(setq wid (getdist "New Polyline Width: ")) ;not negative (foreach ele (sslist (ssget '((0 . "*POLYLINE")))) ;only PLINES (command "_PEDIT" ele "_W" wid "")))
[23.4] Create a polyline or spline: with (ENTMAKE) or (COMMAND)
  1. You can create a script-file with a LISP-program and then run it. It seems to be the simpliest way, but I/O errors may occur when reading/writing the script. If your soft is commercial, it must handle such errors.
  2. The second way is to create the entities list and use ENTMAKE. Advantage: fast, in WCS, independent of actual osnaps.
  3. The third solution is based on command and mapcar. It works with Polylines, Splines or Lines. Disadvantage: UCS, Osnaps ;;; Draws a POLYLINE entity from a list of points (same with SPLINE, ;;; or LINE), on the actual UCS, with actual OSNAP settings (defun DRAW-PLINE (pts) (command "_PLINE") (mapcar 'command pts) (command "")) (defun DRAW-SPLINE (pts) (command "_SPLINE") (mapcar 'command pts) ; the pts must be the fitpoints then (command "" "" ""))

[23.5] How to calculate the LENGTH of polylines?
There are two ways:
  1. the obvious, using the AREA command which is quite "noisy" (prints the result), but works even with splines. ;;; add up the LENGTH of all selected objects, NOISY, you can do the ;;; same with AREAs: simply change the last line to (getvar "AREA") (defun C:LEN-OF () (command "_AREA" "_A" "_E") ;add up objects (works in R12+R13) (ssmap 'command (ssget)) ;renamed, pass all elements to AutoCAD (command "" "") ;two returns (getvar "PERIMETER")) ;this is the length
  2. Doing some math, but only for simple entities. Here is best to define some helper functions again. This is also an introduction for the next chapter [24], some bulge trigonometry for curved segments.

    ;;; calculates length of pline, quiet (defun POLY-LENGTH (poly / seg) (apply '+ ; the sum of all single segment lengths (mapcar '(lambda (seg) ;length of segment (if (zerop (car seg)) (distance (cadr seg) (caddr seg)) ;line segment or (abs (arclen seg seg)))) ;curved: see below at [24] (pline-segs poly)))) ;;; returns all group codes of the complex element ;;; (vertices, attributes) as list, similar to (edlgetent) (defun CPLX-LIST (grp ele / lst) (if (= 1 (getval 66 ele)) (progn (setq ele (entnext (entity ele))) (while (and ele (not (istypep ele "SEQEND"))) (setq lst (cons (getval grp ele) lst) ele (entnext ele))) (reverse lst)))) ;;; PLINE-SEGS - Creates a segment list for the polyline pname ;;; as a list of '(bulge p1 p2). A straight line has bulge 0.0 ;;; Compute pts in ECS of pname. Accepts LWPOLYLINE's (defun PLINE-SEGS (pname / pts segs) (setq segs (mapcar 'list (if (istypep pname "LWPOLYLINE") (group-only 42 (entget pname)) (cplx-list 42 pname)) (setq pts (getpts pname)) (rot1 pts))) ; ->[20.1] (if (flagsetp 1 pname) segs ;closed (butlast segs))) ;open: without the last segment, ->[20.1] ;;; Example: (a bit optimized for brevity :) ;;; add up all the lengths of all polylines, QUIET ;;; To accept also other entities, add those to pline-segs (defun C:POLYLEN () (apply '+ (ssmap 'poly-length (ssget '((0 . "*POLYLINE")))))) ; renamed
For the sum of areas use either the noisy AREA command or implement Heron's formula for polygon areas (just for simple closed polygons).

[23.6] How to revert a polyline direction?
Sergei Komarov submitted a REVPOLY.LSP which takes care of bulges and widths too.

A short stdlib version is this:

;;; ignoring any width information (defun POLY-REVERSE (segs) (reverse (mapcar '(lambda (seg) (std-make-seg (std-seg-p2 seg)(std-seg-p1 seg) (- (std-seg-bulge-num seg)))) segs))) (defun C:POLYREV (/ ele) (std-require "ENTMAKE") (if (setq ele (car (entsel "\nRevert Poly: "))) (std-entmake-pline (entget ele '("*")) ; keep EED information (poly-reverse (std-pline-segs ele)))))
[23.7] How to get the CENTER of a polyline? [new]
The centroid of SOLID's has to be extracted with MASSPROP. You can let it write to a file and analyse this then. The centroid of polylines is different to the mean vector. The geometric mean of some pts is simply: (setq n (float (length pts))) (list (/ (apply '+ (mapcar 'car pts)) n) (/ (apply '+ (mapcar 'cadr pts)) n)) The true centriod is more difficult. The stdlib version is at STD-CENTROID-2D
In the stdlib.arx or at (under freebies) are also a better massprop lisp function for solids. Then you do (command "_REGION" ele)...(massprop entlast)...(command "_UNDO" 1) For VLA there's also a massprop property for Acis objects.

[24] Circle/Arc Geometry: BULGE conversion, some trigonometry

[fixed] What is the BULGE in a polyline?

The bulge is the tangent of one forth of the included angle of a curved segment. A bulge 0.0 means a straight segment. Together with the start- and endpoint it is sufficient information to quickly calculate all other required information of a curved segment. A negative bulge is a rotation in clockwise direction ("mathematically negative").

  arclength = radius*angle
  bulge = +/- tan( ang/4 )            (CCW: +, CW -)
  angle = 4 * atan( bulge )
  bulge = +/- ( 2*altitude ) / chord  (CCW: +, CW -)

See also the book "Maximizing AutoLISP" [2] (Note: The R10/11 book -Vol II- contains a wrong bulge formula.)

(bugfixed, wrong formula! Thanks to Sergei Komarov)

;;; converts a bulged segment (bulge pt1 pt2) of a polyline ;;; to a circle (ctr rad). The start- and endpoints are known ;;; therefore the angles too: (angle ctr pt1)(angle ctr pt2) ;;; returns nil on a straight segment! (defun SEG2CIR (seg / bulge p1 p2 cot x y rad dummy) (if (zerop (car seg)) nil (setq bulge (car seg) p1 (cadr seg) p2 (caddr seg) cot (* 0.5 (- (/ 1.0 bf) bf)) x (/ (- (+ (car p1) (car p2)) (* (- (cadr p2) (cadr p1)) cot)) 2.0) y (/ (+ (+ (cadr p1) (cadr p2)) (* (- (car p2) (car p1)) cot)) 2.0) rad (distance (list (car p1) (cadr p1)) (list x y)) dummy (list (list x y) rad) ; return this, I hate progn's ) ) ) ;;; inverse conversion: ;;; calculates segment (bulge p1 p2) of arc ;;; with given circle (ctr rad), start-angle, end-angle (defun ARC2SEG (cir ang1 ang2 / p1 p2) (setq p1 (polar (car cir) ang1 (cadr cir)) p2 (polar (car cir) ang2 (cadr cir))) (list (arc2bul p1 p2 cir) p1 p2) ) ;;; calculates bulge of arc given the arc points and the ;;; circle (ctr rad) [fixed by Serge Pashkov] (defun ARC2BUL (p1 p2 cir / ang) (setq ang (- (angle (car cir) p2) (angle (car cir) p1))) (if (minusp ang) (setq ang (+ (* 2.0 pi) ang))) (tan (/ ang 4.0))) ;;; returns angle of arc (bulge) (defun BUL2ANG (seg / ctr) (- (angle (setq ctr (car (seg2cir seg))) (cadr seg)) (angle ctr (caddr seg)))) ;;; calculates angle of arc given the chord distance and radius (defun ARC2ANG (chord rad) (* 2.0 (atan (/ chord 2.0 (sqrt (- (expt rad 2) (expt (/ chord 2.0) 2) ) ) ) ) ) ) ;;; length of arc = radius*angle, ;;; Note: +/-, you'll need (abs (arclen seg)) for the distance (defun ARCLEN (seg) (* (cadr (seg2cir seg)) ; radius 4.0 (atan (car seg)))) ; angle = 4*atan(bulge) (setq *INFINITY* 1.7e308) ; largest double (defun TAN (z / cosz) ; [fixed] (if (zerop (setq cosz (cos z))) *INFINITY* (/ (sin z) cosz))) (defun DTR (ang)(* pi (/ ang 180.0))) ; degree to radian (defun RTD (ang)(/ (* ang 180.0) pi)) ; radian to degree

[25] DCL: listboxes with tabs or monotext font

Under Windows it's difficult to layout texts because of non-monospaced fonts.

Try it with the tabs attribute in the list_box tile, such as:

tabs = "0 20 40"; (set_tile "listbox" "Layer:\t0\twhite") or try the following to use monospaced characters, the "fixed_width_font" attribute: : list_box { label = "Drawing"; key = "dwglist"; width = 50; fixed_width_font = true; // <- monotext } Also have a look at the detab routine at or STD-DETAB in to convert tabs to spaces.

[26] EED Extended Entity Data: Select, Get and Store

[26.1] Select objects on their EED with (ssget "X") ;;; defines your appname header and delimiter (4 char regapp name ;;; according AAIG, the Autodesk Application Interoperation Guidelines) (setq appname "HUBU-") ;;; defines * for all sub types (setq allappnames (strcat appname "*")) ;;; eg: HUBU-LIST1, HUBU-LIST2 ;;; here is how to get the eed list from one element (defun GETEED-LST (ele) (cdadr (assoc -3 (entget ele (list allappnames))))) ;;; this gets all elements of appnames typ (wildcards allowed) (defun SSGET-APP (typ) (ssget "X" (list (list -3 (list typ)))) ;;; this gets only your elements (defun SSGET-HUBU (typ) (ssget "X" (list (list -3 (list (strcat appname typ))))) (ssget-hubu "*") ; will get all your elements
[26.2] Get EED from an object

Check any XDATA with: (entget (car (entsel)) '("*"))

These functions return all XDATA matching the regapp name or all matching XDATA code values.

;;; get all XDATA lists from an element ;;; i.e with XDATA: ;;; (-3 ("HUBU-1" (1000 ."ASSHATCH")(1002 ."{") ;;; (1070 . 1)(1002 ."}"))) ;;; =>(("HUBU-1" (1000 ."ASSHATCH")(1002 ."{")(1070 . 1)(1002 ."}"))) (defun GETXDATA (e apnlst) (cdr (assoc -3 (entget e apnlst)))) ;;; all lists without the regapp name ;;; => ((1000 ."ASSHATCH")(1002 ."{")(1070 . 1)(1002 ."}")) (defun GETXDATA-ALL (e apnlst) (apply 'append (mapcar 'cdr (getxdata e apnlst)))) The regapp name is stripped here, because it's only used for fast ssget access. The different apps are divided by different (1000 . name) groups as it's used by Autodesk.

For storing XDATA in an element see XDATA.LSP or XED.LSP though those examples are a bit disturbing.

For advanced EED tricks, esp. converting the "{" "}" ADS resbuf style to Lisp lists and back see

[27] How do I send a Ctrl-C to a command?

Also: "How do I press Break in AutoLISP?"

(COMMAND) without parameters works just like hitting Ctrl-C under DOS or ESC under Windows at the command prompt. But it does not mimic ESC in a dialog box. And it does not work within SCRIPTS. (command nil) is the same as (COMMAND).

(command) breaks only the command functions, e.g. if you use the command "DIM" inside AutoLISP, you must interrupt it by (COMMAND) after dimensioning.

But it doesn't work, if you try to interrupt a lisp loop. There is another function (EXIT) or (QUIT) -they do the same-, which immediately break a Lisp program.


(while T ; do ; a never ending loop (princ "\nEnter a=") (setq a (getint)) (if (zerop a)(exit)) ; Breaks Lisp and returns to the command mode. ) In this example (COMMAND) doesn't work. (EXIT) works exactly as Ctrl-C. It prints "error: quit / exit abort" and outputs all nested functions. To provide "silent" break you must include this error message to an error handling function, e.g.: (setq *olderr* *error* *error* my-error) (defun MY-ERROR (s) (if (not (member s ; msgs of the english version: '("Function cancelled" "console break" "quit / exit abort"))) (princ (strcat "\nError: " s)) ) (setq *error* *olderr*) )

For scripts use this workaround by defining (cancel) in lisp, simply

(defun SCRIPT-CANCEL () (command) (command "resume") ) and in a SCRIPT.SCR: .. [script commands] (script-cancel) [more script commands] ..

[27.1] How to do an unlimited number of user prompts?

[new] To let the user end any selected command without having to write code for every possible option, just repeat (command PAUSE) until the command is ended. (command "_ARC") (while (= 1 (logand (getvar "CMDACTIVE") 1)) (command PAUSE))

[28] How to decode ACIS internal geometry with Lisp?

All the ACIS objects (3DSOLID) have been documented by Spatial ("SAT Format Description"). However the internal representation by (ENTGET) is still encrypted, but the encryption scheme was hacked. (XOR 95)

Samples and code are at: [new]

[A] Disclaimer, Notes from the authors

If you think of questions that are appropriate for this FAQ, or would like to improve an answer, please send email to Reini Urban <> but don't expect an reply.

This AutoLISP FAQ is Copyright (c) 1996,97,98,99 by Reini Urban.
The sample code is, if not otherwise stated, (c) 1991-97 by Reini Urban and may be freely used, copied, modified and distributed, but not sold.
The basic functions are, if not otherwise stated, (c) 1991-97 by Reini Urban and may be freely used, copied, modified and distributed.

This FAQ may be freely redistributed in its entirety without modification provided that this copyright notice is not removed. It may not be sold for profit or incorporated in commercial documents (e.g., published for sale on CD-ROM, floppy disks, books, magazines, or other print form) without the prior written permission of the copyright holder. Permission is expressly granted for this document to be made available for file transfer from installations offering unrestricted anonymous file transfer on the Internet and esp. to be included into the official AutoCAD FAQ.

If this FAQ is reproduced in offline media (e.g., CD-ROM, print form, etc.), a complimentary copy should be sent to Reini Urban, X-RAY, Nibelungeng. 3, 8010 Graz, Austria

This article, the contents and the sample code, is provided AS IS without any expressed or implied warranty.

[A.1] FAQ Locations
Homepage of the HTML'ified version:
Annotated AcadWiki version: [new]
The posted ascii versions (and always latest versions) are at
The Winhelp version (zipped with faq-code.lsp) is at
The FAQ usenet archive is at or at
The Lisp code from this FAQ is at
A french translation of the FAQ was made by Roger Rosec
A japanese translation of the FAQ was made by MASAMI Chikahiro
A russian translation by Igor Orellana [fixed]
A german translation by Reini Urban
A spanish translation by Eduardo Magdalena [new]
A greek translation is in progress.
Relevant AutoDesk FAQ's
AutoCAD Techsupport
[changed] Search AutoCAD+FAQ
Support Assistant 2000 [fixed]
AutoDesk news groups [changed]
news://, at Google [new] or the new WebX interface at Autodesk's new discussion server.

[B] Acknowledgements

This FAQ is based on great efforts of the comp.cad.autocad community, in particular:

Tom Berger, Adi Buturovic, Christoph Candido, Mike Clark, Miles Constable, Cara Denko, T.J. DiTullio, Chris Ehly, Jeff Foster, Rusty Gesner, William Kiernan, Paul Kohut, Sergei M. Komarov, Joseph M. Liston, Lu, Eduardo Magdalena, Masami Chikahiro, Georg Mischler, Desi Moreno, Vladimir Nesterovsky, Roger Rosec, Serge Pashkov, Dennis Shinn, Tony Tanzillo, Eugene Tenenbaum, Reinaldo Togores, Reini Urban, Serge Volkov, Morten Warankov, Owen Wengerd, Alan Williams, Doug Wilson, Ian A. White, David Whynot, Darren Young, Xiang Zhu and many others.

[C] Recent Changes

25.Jun 2002
new spanish translation [A.1]
3.Mar 2002
Vladimir added a section to [11] S::STARTUP (from the wiki)
18.Jun 2001
fixed to
23.Apr 2001
fixed several links
v2.28 4.Apr 2001
changed rurban@sbox to (defunct in the next year), all parts of the faq are now in the acadwiki.
v2.27 23.Sep 2000
added [23.7] "How to get the CENTER of a polyline?"
15.Sep 2000
changed stack-overflow [14] to better reflect VL/VLIDE, A2000
new book [2]
1.Sep 2000
vl-sort warning with duplicate entries [8]
18.Aug 2000
changed Codemagic [6.1] from Freeware to Shareware, thanks to Nir Sullam
1.Aug 2000
changed adesk faq locations to search url
v2.266.Jun 2000
added LDATA bug [7], fixed DEFUN-Q [11], removed most colored [new/changed] notes
v2.25 17.May 2000
added [27.1], added C:POLYREV [23.6], texinfo versions
25.Apr 2000
added Point A [1.1], shortened the DDE example in [21.2]
24.Apr 2000
Vladimir fixed to [1.1]
v2.24 20.Apr 2000
renamed to [1], added [1], added rapidlisp [6.2], (added emacs folding)
30.Mar 2000
renamed to
9.Mar 2000
added CodeMagic editor at [6.1], thanks to Nir Sullam
29.Feb 2000
Masami Chikahiro fixed numeric ranges [7]: -32766 => -32768
23.Feb 2000
Phil Kenewell updated LispLink 2000 [6.1].
17.Feb 2000
Added the dotsoft biglist url [7].
Mike Tuersley fixed [11] for MNL files.
v2.23 14.Feb 2000
Chris Ehly fixed all broken links.
v2.22 13.Jan 2000
additions to numerical precision. adesk techdocs links are broken again. compiled S::STARTUP hooks
v2.216.Dec 99
adesk faq link, removed peoples urls/emails, minor fixes.
7.Oct 99
wording in [0.1], german translation, link in [28]
v2.2 13.Jul 99
added topics [0.1] What changed with AutoCAD 2000?, [0.2] Why cannot I create ARX anymore?, [5.4] Better ones: Common Lisp and Scheme.
additions to [6.2] Analyzers, Packagers..., [5.3] R15 VLISP info, [4] FAS Security, [21.4], [20.4]: renamed SSAPPLY to SSMAP
13.Apr 99
fixed a link [1]
v2.1 3.Jan 99
fixed and added some links: [22.4], [A.1], [B], [27], [1], [2], [20], [22.1]
21.Dec 98
found a russian translation, bob jones' and masami chikahiro's links are broken
12.Jul 98
changed posting frequency to monthly. Some minor fixes concerning the now available Visual Lisp and other cosmetics. cadsyst url
6.Jun 98
changed Eugene's email (and back at 18.Jul)
13.May 98
added R14 plotdialog [21.2]
11.May 98
bugfixes by Serge Pashkov <> in [24] arc2bul, [20.1] remove-if-not (but correct in faq-code.lsp), [21.7] doc of maptrans0-1, [24] tan, [21.2] DDECMD and some vlisp beta1 fixes in faq-code.lsp
v2.0 7.May 98
lots of Visual Lisp based changes: [0],[4],[5],[6.1],[7]
[17] new, [2] new books, [21.2] ActiveX sample, [A.1]better official R14 FAQ
27.Feb 98
[0] Visual Lisp available.
24.Feb 98
[6.1] lspedit.exe, [0] Visual Lisp news and [7] entmake vertex
v1.12 12.Feb 98
Eugene Tenenbaum <> send me huge list of corrections, mostly improving the english language. This time only up to [11].
15.Jan 98
[7] HATCH added to entget problem,
[0] more specific now, [22.4] url change [A.1] Japanese translation
[2] The R13 lisp manual is in the cust. manual not only on the cd. sorry
Vladimir Nesterowsky's new web url
fixed some typos
v1.11 15.Nov.97
changed header.
Autodesk AutoCAD FAQ URL's. see [A.1]
LispLink editor. see [6.1]
Zoomer rumors: [0]
Roger Rosec provided a french translation of the entire FAQ. see [A.1]
13.Sep 97
Alan Williams detected a stupid error in DATESTAMP in [22.2] but in FAQ-CODE.LSP it was okay.
28.Aug 97
added the (entget) LWPLOYLINE bug to [7],
changed my mail address to to be prepared for the after-student area. :)
v1.10 22.Jul 97
some LWPOLYLINE fixes, R14 Lisp debugger Vital LISP 3.0 shipped, Convert 3.3 update [4.4], fixed cronjob for bi-weekly posting: every 2nd Monday, 11.30 MET
20.Jul 97
Vital LISP 3.0 shipped
12.Jul 97
Convert 3.3 update [4.4], fixed cronjob for bi-weekly posting: every 2nd Monday, 18.00 MET
2.July 97
fixed URL in [10],
30.June 97
fixed (istypep) in [20.4], changed title of [16], light changes in (getpts) in [23.1]
v1.9 26.June 97
[5.2] confirmed Vill3 release date, added DDE sample from Xiang Zhu to [21.2], provided detab.lsp [25]
17.June 97
bugfix in [20.4]: short (getval), [12] R14 ARX autoloading, [23.5] (pline-segs) is now R14-save but still not compatible, new [23.6] revpoly.lsp, [A.1], [5.2] Vill 3 will have reactor support.
9.June 97
new symbol-string trick by Christoph Candido [20.3]
21.May 97
some minor corrections.
v1.8 15.May 97
added [0] Future of AutoLISP?
changed VERTECES to VERTICES, fixed mail address of,
added SSAPPLY: [20.4], [23.5],
started to R14'ify some code for LWPOLYLINE's [23], not finished yet, (pline-segs) is missing
9.May 97
[2.1] R14 Winhelps, [5.2]: new basis url, Vill Lite [6.1]
added [16]: Lisp over mult. dwg's
added some short comments to [6.1](ntemacs), [14], [21.8]
21.April 97
added [[28] ACIS decryption
v1.7 9.April 97
added [[21.8] C:XYZ,
added [[15] (command "ROTATE3D") does not work! Why?
HTML version chapter numbers match the posted version,
added [27]: (command) as ctrl-c, Sergei Komarov improved [27], Adi Buturovic improved [27] for scripts.
v1.6 13.Feb 97
moved the intro to the very beginning for the curious.
another lisp plot lisp [21.2], a third lisp debugger [3.1], [A.1]: the gd.tuwien uunet mirror is faster than the official ones, fixed cadence FAQ url, applied digest format partially, html will be created automatically soon, wrong (old) chapter numbering from the v1.5 version, [7] 64 in flag 70 in symbol tables,
v1.5 5.Feb 97
added get and edlgetent samples by Vladimir, removed the sort code instead,
changed [11] title and added string funcnames,
bugfix in getpts [23.1], basic funcs should be free [A],
added DATESTAMP to [22.2], added a "s" to [A] title,
added [20] DCL, [21] EED, [21.1-21.7] samples,
Serguei Komarov found a bug in seg2cir,arclen,arc2bul [24],
added arc2ang and (corrected) arclen,
bugfixes in sslist, getval, all predicates with "p" postfix now,
prepared a FAQ-CODE.LSP, Convert supercedes Decrypt [4.4], added scripts and (command) to [23.4], AREA to [23.5],
v1.4 24.Jan 97
important news with Decrypt [4.4],
moved [11] "bugs" to [7] "problems",
added [11] "How do I (sym, list)" instead,
added the "Approved" header for news.answers processing,
added [22]-[24]: some examples for subentities and bulge stuff,
Serge found a bug/feature in acad_strlsort [7],
added number accuracy and ss limitation to [7],
added break code and samples to [3.3],
added a short lisp style guide at [2.2], instead of [6.4]
v1.3 17.Jan 97
added [16] stack overflow (thanks Serge), [4.7] Lisp2C,
updated [8] fastest sort (sample, benches),
received the news.anwsers approval
v1.2 11.Jan 97
added Phoaks to news archive
fixed (break) in [3.3] (Thanks Tony),
added a sorting example to [8], improved (my-princ) in [15]
changed posting frequency from weekly to bi-weekly
v1.1 4.Jan 97
R13 bugs, S::STARTUP code by Owen Wengerd,
homepages instead of e-mail adresses where appropriate, (people get enough junk mail these days)
more links, and some bugfixes
v1.0 22.Dec 96
First version, posted on 28.Dec 96
as a discussion basis