eq and hashing (was Re: [plt-scheme] How to make unit functors?)

----- Original Message ----- 
From: "Matthew Flatt" <mflatt at cs.utah.edu>
> 
> The bottom line is that `eq-hash-code' isn't always the right thing,
> just as `eq?' isn't always the right thing. But `eq?' is sometimes
> sufficient, and so is `eq-hash-code'.
> 

It seems bizarre that EQ?, which is the right thing for (interned) symbols
doesn't play well with EQ-HASH-CODE when you use them together
on interned symbols.