[racket] I've implemented a Scheme Interpreter. But it's too slow. Next step?

> A common trick is to embed type information into the pointers.
> In the representation used in the 1996 Scheme Workshop pointers to cons
> cells contains 010 in their lower 3 bits. A type check is thus compiled
> to a very fast and instruction.
>
> http://www.cs.indiana.edu/eip/compile/back.html

David Guderman's survey paper "Representing Type Information in
Dynamically Typed Languages" talks about representation strategies:

    http://lambda-the-ultimate.org/node/3912