Is there a working example of type families usage?

21 Apr 2015

      I tried this:

|{-# LANGUAGE TypeFamilies #-}

class  C  xwhere
   type  A  x
|

It fails with this error:

|Temp/jhc1.hs:4   - Error: parse error at "}"
|

Standalone type families don’t work either:

|{-# LANGUAGE TypeFamilies #-}

type  family  A  x
|

|Temp/jhc1.hs:3   - Error: parse error at "family"
|

Is there an example somewhere that I missed while googling?

Artyom