[racket] Typed racket puzzle (ii)

On Wed, Aug 17, 2011 at 10:32 AM, Shriram Krishnamurthi <sk at cs.brown.edu> wrote:
>> Jon Postel summed up contravariance by thinking about HTML: "Be
>> liberal in what you accept, and conservative in what you send."
>
> That's cute, except that Postel's law is arguably a source of security
> holes, so it's probably not the best analogy. (-:
>
> Shriram
>

That's my segue to dire warnings about reflection. This is wildly
off-topic for the list, so I shunted the responses to Norman looking
for contravariance of functions in category theory and Shriram blaming
my analogies for poor security to a lunch-break page.

<http://www.arcadianvisions.com/downloads/ContravariantFunctors.html>

Anthony