language creation

Is it possible to write a programming language with an existing one?  I want to create a game creation program, and have it use it's own language for additional programming.  Something similar to Game Maker.

How does functional programming hurt maintainability? Supposedly abstraction and parameterizing improve maintainability, at least that is what people who emphasize agile methods and refactoring suggest.

I don't know what you used, I know that SML derivatives are quite fast because a strict type system allows the compilers to make all sorts of lovely optimizations beyond tail calls. I use OCaml for realtime audio synthesis and it holds up quite well against C.

Well I did recommend Lua didn't I, so imperative can't be that bad. Imperative is rather straight forward but it is pretty limited, usually functional languages allow for more code reuse through parametric polymorphism etc. I would argue that you write more code in an imperative style. For a game wouldn't it make more sense to have reusable chunks of logic you can pass about (I know you can pass functions in Lua). This is especially relevant for AI.

I explicitly recommended SML as it provides you with meta-language capabilities, you can extend SML without changing SML very much, you can also extend it in such a way that it can be compiled, you could generate C code and compile that if you wanted to.