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CAD tip CAD tip # 13683:

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Limitations of the LISP language (AutoLISP, VisualLISP) in AutoCAD LT - what to watch out for

A - answer Starting with AutoCAD LT 2024, it is possible to run LISP applications, commands and files in .LSP, .FAS or .VLX (and .DCL) format in AutoCAD LT. However, LT version has some limitations compared to full AutoCAD in LISP support. Most of the existing LISP applications will work without any problems, but some may end with an error or fail to produce the expected result.

Thus, of all the Arkance Systems (CAD Studio) LISP applications - see Download - most will also work, but some (e.g. Click2XLS, DTM, SureSave...) will have the limitations mentioned below. None of these applications will offer the new version notification in LT.


The first type of limitation is the lack of support for external ActiveX objects. For them you cannot use the (vlax-create-object), (vlax-get-object), (vlax-get-or-create-object), (vlax-import-type-library), (vla-GetInterfaceObject) functions. These functions are typically used for online communication, clipboard handling, XML, binary files, Excel, Word, Access (or other database tools), etc.

E.g the call:

(vlax-create-object "Microsoft.XMLHTTP")

returns nil and the web "communicator" object is not created.

Another, quite logical limitation is working with 3D DWG objects (plus render tools, databases...). These are not supported in LT version and therefore you cannot use (command) to call unsupported commands (or access variables), nor can you create or modify 3D objects via (entmake), (entmakex), (entmod).

E.g. the construction:

(entmake (list (cons 0 "3DFACE")(cons 10 (car triangle))(cons 11 (cadr triangle))(cons 12 (caddr triangle))(cons 13 (caddr triangle))))

returns nil and the entity of type 3DFACE is not created (silent fail, no error is reported).

You cannot access XRecords, used by some LISP applications to store data in dictionaries.

You also can't use Express Tools commands or its libraries or "acet-" functions in LT. Of course, you can't call VBA or ARX or .NET functions either.

Automatic loading of LISP functions from ACADDOC.LSP must be done in the LT version in the ACADLTDOC.LSP file. Also, .MNL files (with CUIx menu files) are not automatically loaded. The LT version does not work with profiles. And there is no AI_UTILS.LSP preinstalled.

Note that the LT version does not have a LISP editor (IDE, the VLIDE command) and therefore no debugger or compiler or linker. You can switch Unicode support though - LISPSYS. You cannot use (vlisp-compile) to compile LSP files either.

You can use the .bundle autoload mechanism in LT (the folder Autodesk/ApplicationPlugins). Don't forget to add Platform="ACADLT" to the RuntimeRequirements section in your PackageContents.xml file.

The AutoCAD LT for Mac version has other limitations - e.g. you cannot use ActiveX functions (vlax-), reactors, etc.

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1.4.2023    3148×   FAQ  
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applies to: AutoCAD LT 2024 ·

See also:
Tip 13529:How to redefine the behavior of a standard AutoCAD command?
Tip 12926:How to import point coordinates from Excel to AutoCAD?
Tip 12287:AutoCAD hatch flood-fill does not honor all boundaries.
Tip 12084:Three methods of adding line lengths in AutoCAD.
Tip 11714:How to assign a RAL color to a DWG object and get its ACI equivalent?

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