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LISP interface

During the programming works to port "LayerManager Professional" to AutoCAD LT, there were some very interesting effects shown normally, "LayerManager Professional" should not be able to run properly, because a small number of LayerManager's internal technologies are based on communication with and using AutoLisp, that is not existing under AutoCAD LT, as commonly known


After some further investigations it becomes clear : even when running AutoCAD LT the AutoLisp interface is completely present and active as known from AutoCAD !


But AutoLisp was handicaped by Autodesk in some important details: at first, AutoLisp is not active at the command prompt, and both functions (load lispprogram) und (arxload arxprogram) have been removed. So it looks as there would be no chance to get into AutoLisp, as first impression


During development of LT-Extender 2000 Plus, a special technology was built which enables the access to AutoLisp in usual manner the most interesting and important fact is, that LT-Extender uses the original, built-in AutoLisp, in opposite to other Lisp-enabling software. This ensures highest performance, compatibility and stability in the context of AutoLisp under AutoCAD LT.


Features of AutoLisp-Activation:

  1. complete compatibility at applications' level: this means, that AutoLisp applications will run even under AutoCAD LT without differences and limitations

  2. both that missing AutoLisp functions (load lispprogram) and (arxload arxprogram) are provided by LT-Extender in compatible way

  3. AutoLisp applications may use Standard-AutoLisp, Protected-AutoLisp and Kelvinated-AutoLisp

  4. nested and recursive loads of AutoLisp applications is working properly

  5. an interactive Lisp prompt is provided to enter and evaluate Lisp expressions; this is an alternative and replacement for the missing Lisp evaluation at the command prompt


There were intensive tests made to ensure compatibility and stability of the AutoLisp integration: even most complex AutoLisp applications with more than 1 MByte of program code were completely working without any problems and with full performance. It was very interesting to recognize, that applications usually run just faster under AutoCAD LT compared with AutoCAD - because AutoCAD LT is smaller and does not have so much overhead, the overall performance is just better an interesting side-effect !


There are only 2 limitations known for using AutoLisp under AutoCAD LT at this moment:

  1. there is no possibility for using VisualLisp files (*.fas, *.vlx) (we are working on that)

  2. AutoLisp applications using those programming interfaces of several AutoCAD-Extentions (MAP, ADT, LDDT etc.) will not work, because these interfaces are not available under LT