Earlier quoted context omitted.
I thought this was one of the notably bad talks this year. The whole premise that a function of Maybe a should be a function of a without an API change is neither intuitive to me nor really justified by Hickey. Different things are different. It's sad to see someone build such a wall around himself when faced by something (type theory) that he doesn't understand.
>that a function of Maybe a should be a function of a without an API change is neither intuitive to me nor really justified by Hickey He spent many minutes motivating it. If you support some functionality to a client (as a library, or a service, or more abstractly), and then later want to relax the constraints that you require from those clients, this should be an acceptable change that they shouldn't have to worry a…
Union Types don't compose straightforwardly because they flatten; maybe this is desirable in some cases but the rationale in Hickey's talk leaves me unconvinced. The only practical use case for union types I'm aware of is smoother interfacing to dynamically typed APIs; any nice examples for something beyond that?