What is the difference between packages GCL and CLISP?

Question

In the Ubuntu repositories there are two implementations of Lisp: GCL and CLISP. Is there a fundamental difference between them? Which one is closer to the industry standard?

Answer 1

Common Lisp is actually defined in an ANSI standard. There are lots of implementations for it, both commercial and FOSS. The implementations generally comply with the standard, and provide some extensions of their own for things that are not defined in the standard (such as threads, FFI and unicode).

You should see http://www.cliki.net/Common%20Lisp%20implementation for a comparison of implementations. Which one you should use depends on your needs and preferences. For starting out you can just pick one. The language itself is going to be the same regardless, and as long as you don't use any implementation specific extensions, you can easily switch to another one if needed.

I personally prefer SBCL on Linux. It has good performance and includes extensions for threads and all. The main weakness is that programs will be very large (both disk space and memory usage). That doesn't matter much if you're building a server side app, or something so big that it outweighs the implementation anyway, but for smaller client-side tools you might want to look into CLISP. I haven't used GCL, so I can't say much about it.