Re: [Haskell-cafe] [ghc-proposals/cafe] Partially applied type families

On Jun 4, 2017, at 4:06 AM, Anthony Clayden wrote:

OK, concrete example:

I'm afraid I don't see the concrete example. I was expecting an example of how today's TypeError doesn't work for you. But it looks like the example you give is one motivating instance guards... but I'm not quite sure of that, either. I find these examples are clearest when they include code that you want to write, but can't; or code that behaves a certain way, but you want different behavior. And indeed maybe that's in your example, but I didn't see it. Thanks, Richard