On: Covariance and Contravariance

[mikeash]

I don't know much Scala, and my blog is mostly focused on the Apple world.

That said, I always love seeing other perspectives, so a comment on the article describing how Scala gets it right would be welcome.

[chengl → mikeash]

here you go. Variance explained by Martin Odersky in his coursera course https://class.coursera.org/progfun-005/lecture/83 (you need to login to watch it). Or the Scala doc http://docs.scala-lang.org/tutorials/tour/variances.html