Type Classes
============

PureScript has basic support for type classes via the `class` and `instance` keywords. 

Type class instances must be of the form `String`, `Number`, `Boolean`, `[t]` or `C t1 ... tn`, and only a single type class parameter is supported.

Type class instances are resolved based on the order in which they appeared in the source files. In particular, overlapping instances are permitted.

Here is an example of the `Show` typeclass, with instances for Strings, Booleans and arrays::

  class Show a where
    show :: a -> String
  
  instance Show String where
    show s = s
  
  instance Show Boolean where
    show true = "true"
    show false = "false"
  
  instance (Show a) => Show [a] where
    show [] = "[]"
    show (x:xs) = show x ++ " : " ++ showArray xs
  
  example = show [true, false]