The Lisp Machine actually supported at least two languages that I know of; Lisp Machine lisp and later they added Common Lisp. Common Lisp is a very good multi

The Lisp Machine actually supported at least two languages that I know of; Lisp Machine lisp and later they added Common Lisp. Common Lisp is a very good multi-paradigm language; it can accommodate any style of program you want to write. It's designed so that you can extend it to be the right language for your problem, rather than to be a good language for one type of program. Integrating a non-lisp language wouldn't be impossible, but might be hard. How would Haskell's type inference work when you're calling a Lisp function? What would happen if a C program dereferenced a pointer to a Lisp object? There are no immediately obvious answers to these questions, although these days there are precedents.