contravariant argument types: wanna?

[Justin Johansson]

Andrei Alexandrescu Wrote:

> Today D does not support contravariant arguments, but Walter told me 
> once he'd be quite willing to implement them. It is definitely the right 
> thing to do, but Walter would want to see a compelling example before 
> getting to work.
> 
> Is there interest in contravariant argument types? If so, do you know of 
> a killer example?

FWIW, some background reading material which might be useful to others.

http://en.wikipedia.org/wiki/Covariance_and_contravariance_(computer_science)

http://www.icsi.berkeley.edu/~sather/Documentation/EclecticTutorial/node5.html

A lot to digest in the following paper but looks like multiple dispatch might be the killer example ???

http://cs-people.bu.edu/jhallett/papers/oops07.pdf

-- Justin Johansson