Yeah, but that's wrong. It's the usual confusion about Just in Time dynamic compilation by the system and incremental compilation by the user. LISP I had an in

Yeah, but that's wrong. It's the usual confusion about Just in Time dynamic compilation by the system and incremental compilation by the user. LISP I had an incremental compiler. The user calls the compiler with a list of functions or function definitions to compile. It's not compiling dynamic by the system and also does not use information about the running function (call statistics, call argument statistics, ...). There is no "Just in Time" functionality provided. The developer is responsible to decide what code to compile and when to compile the code. A function needs to be compiled by the developer before it is invoked, otherwise it won't run compiled. In a JIT compiled setting the system decides when to compile the code: either on start or during runtime triggered by the system. The code will be "Just in Time" compiled. This Wikipedia article explains the difference: https://en.wikipedia.org/wiki/Dynamic_compilation https://en.wikipedia.org/wiki/Dynamic_compilation "Just-in-time compilation is a form of dynamic compilation." "Unlike dynamic compilation, as defined above, incremental compilation does not involve further optimisations after the program is first run." Later Lisp systems may have aspects of JIT compilation. For example some CLOS implementations optimize code (-> method combinations) at runtime, possibly via compilation.