Common Lisp at CoCreate (29 Dec 2007)

CoCreate OneSpace Modeling is a 3D CAD modeler built on a concept called "explicit modeling". C++ is used mainly in the modeling kernel, while Lisp dominates the UI, the application logic, many add-on modules, and the API. The Lisp part of the project is safely in the 7-digit lines of code range. I don't know much about the other large Lisp projects out there, and LOC isn't exactly the greatest way to compare application complexity anyway, so I'll play safe and just say that this is certainly a non-trivial Common Lisp project.

Back in 1995, when we were still a division of Hewlett-Packard, we published an article in "HP Journal" which outlines why we chose Common Lisp and what we're doing with it in the product. The article is still available at http://www.hpl.hp.com/hpjournal/95oct/oct95a7.pdf. Since then, the application changed a lot, of course - we even renamed it twice But much of what is said in the article about Lisp still applies.

The HP Journal article concluded:

Common Lisp is also used as a user accessible extension language for HP PE/SolidDesigner. It is a standardized, open programming language, not a proprietary one as in HP PE/ME10 and PE/ME30, and the developers of HP PE/SolidDesigner believe that this will prove to be an immense advantage.

SolidDesigner was the original product name; ME10 and ME30 were predecessor products which implemented their own little macro interpreters. Back then, we were a bit cautious about the potential benefits we'd reap, as the product was still in its early days. By now, however, we can say that Common Lisp was a key factor in helping a fairly small team of developers keep pace with the big guns in the industry, due to all the well-known productivity features in Lisp, such as macros, the REPL, or automatic memory management.

The HP Journal article describes how we use macros to define a domain-specific language called action routines, which are state machines which guide users through commands. Later, we extended that concept by automatically generating UI for those commands: Using the sd-defdialog macro, application developers can implement full-blown commands in just a few lines of code, without having to write any (or at least hardly any) code for services such as:

• Automatic "macro recording" of commands
• Context-sensitive online help
• UNDO support
• Command customization (commands can be started from toolbars, menus, a user input line, or from our "taskbar")
• Sequence control (dependencies of user inputs on other input)
• UI creation and layout
• Adherence to UI style guides
• Graphical feedback both in the UI and in 3D graphics windows
• Type and range checks for input data
• Automatic unit conversions (imperial to metric etc.)
• Prompting

I've been planning to blog more on sd-defdialog for some time, and hope to get around to it Real Soon Now.

Needless to mention, I guess, that I made sure that CoCreate is now also part of Peter's great list... .-)

PS: If you're interested, check out my other blog posts related to CoCreate Modeling or the CoCreate Modeling FAQ.

Previous month: Click here.

to top