`defprotocol` and `extend-protocol` remind me of type classes and type class instances in Haskell. The latter provide the same kind of ad-hoc polymorphism - i.

`defprotocol` and `extend-protocol` remind me of type classes and type class instances in Haskell. The latter provide the same kind of ad-hoc polymorphism - i.e. you can tell the compiler that your custom datatype implements a predefined protocol, and then code that talks to that protocol automatically works with your new datatype, in a statically type-safe and (I believe) efficient way. For example, this (built-in) type class is similar to Java's `toString()`: class Show a where show :: a -> String -- works with any instance of Show showTwice :: (Show a) => a -> String showTwice s = show s ++ show s data Fruit = Orange | Apple instance Show Fruit where show Orange = "orange" show Apple = "apple" x = Orange show x -- => "orangeorange" Can anyone more familiar with Clojure (or Haskell for that matter) compare and contrast?