Pico Lisp: A Radical Approach to Application Development describes a minimalist Lisp interpreter which has been used to build real applications for ~20 years. If you ignore the tendency toward self-aggrandizing, there's some food for thought here. Pico Lisp only has native support for symbols, integers, and lists (no arrays, no structures), and is implemented as a straightfoward interpreter. Yet in the benchmarks (usual disclaimers here), Pico Lisp fares well against a compiled Lisp. Is there a case to be made for ultra lean and mean interpreters as a viable alternative to compilers?