Board with an embedded scheme interpreter

I've spent long nights meditating on this and I think I have a design that could work.

Commands are normal scheme expressions embedded in text, for example a post body of "Hello, number (+ 2 3)" would output "Hello, number 5". Literal parenthesis would need to be escaped with a backslash. All expressions are evaluated and their output displayed except for define expressions, which are both evaluated and displayed.

Each thread is roughly equivalent to a scheme session. Names defined in parent posts are available to subsequent posts in the thread. Names are immutable within a thread; symbols cannot be redefined.

Obviously a set of primitives should be provided: the basic arithmetic operations; a display operation; a set of formatting operations roughly equivalent in capability to today's BBCode; and, of course, our old friends cons, car and cudder.

What say you, /prog/? Can we do this thing?

>>10
Mutable names would let the posters above you redefine + and maybe display. I guess that could be fun though.

I think (>>1) should display the content of post 1, though I'm not at all sure. Should ("hello") output hello or should it be an error? It'd be nice to do (b >>1), (rot13 >>1), (gpl >>1) and (faggot-quote >>1). Including other threads would be interesting. Some sort of library inclusion mechanism is needed I think.