[racket] Pattern matching define macro

Brian Adkins wrote at 07/12/2014 04:19 PM:
> Thanks for the advice Neil. I'm a little confused by your "Racket is an imperative language" statement though - it seems quite "functional" to me, which was one of the attractions.
[...]

Racket can be used as a functional language, so long as one remembers 
that it's mostly an algorithmic language with an imperative and 
sequential evaluation model, with not much obvious magic.

I often see Racket code that (among other problems) looks like the 
programmer sometimes thinks they are using a declarative language, or 
code that would be more defensible if Racket were doing lazy 
evaluation.  What should be O(1) becomes O(n), O(n) becomes O(n^2), 
constant cost per n increases orders of magnitude unnecessarily, etc.

I think that Racket's closure application is pretty easy to understand 
if people are sat down and walked through it.  I suspect people get 
confused by having lots of different models thrown at them, or they 
kinda skip over the evaluation model introductory info, or they're 
exposed to the evaluation model very early on (while overwhelmed with 
concepts) but then don't go back and re-learn the intro stuff later 
(after they have internalized more context to anchor).

Neil V.