[Haskell-cafe] Most Important GHC extensions to learn/use?

[Gábor Lehel]

On Fri, Jun 1, 2012 at 6:29 AM, wren ng thornton <wren at freegeek.org> wrote:
>
>    TypeFamilies (aka TFs)
>        These are really nifty and they're all the rage these days. In
>        a formal sense they're equivalent to fundeps, but in practice
>        they're weaker than fundeps.

Is that still true? The reason used to be that we didn't have
superclass equalities, but we do have them now since 7.2. The only
drawbacks I know of relative to FDs are that it's sometimes more
typing, not supported by GeneralizedNewtypeDeriving, and doesn't allow
OverlappingInstances (ick).