> We also need tools for abstracting and generalising these notions, so that composition goes from being a syntactic disaster to a semantic convenience. I've b

> We also need tools for abstracting and generalising these notions, so that composition goes from being a syntactic disaster to a semantic convenience. I've been speculating for a while that the problem with Java's checked exceptions was principally the impoverished language we had to talk about them. If we could write things like "this throws anything the argument throws, except XYZ" things... might've turned out considerably differently.