On Sunday, January 10, 2016 at 6:34:09 AM UTC+8, Mauro wrote: > > > It would be interesting to learn why this is the case because I would > think it should be. > > Have you read through the, I think linked, wikipedia article? You only > need to read the Array section: > > https://en.wikipedia.org/wiki/Covariance_and_contravariance_%28computer_science%29#Arrays > >
Hi Mauro, Thanks for the link. That does explain it in the sense that I now know Vector is invariant in Julia, but that begs the question, can we specify a constructor to be covariant or contravariant in Julia? One of my longer terms dreams is to be able to do category theory in Julia similar to Haskell <https://en.wikibooks.org/wiki/Haskell/Category_theory>. It seems this would be important to do categories properly.
