Is that where he borrowed it from? I've seen mention of the language feature showing up in Eiffel, Sather, and so on. http://en.wikipedia.org/wiki/Covariance_

Is that where he borrowed it from? I've seen mention of the language feature showing up in Eiffel, Sather, and so on. http://en.wikipedia.org/wiki/Covariance_and_contravariance_(computer_science) http://en.wikipedia.org/wiki/Covariance_and_contravariance_(...