---
-- This module provides functions for countable 
-- objects. Well, it is just an example for HDoc, so don't ask me what
-- it is good for. More inforation about HDoc is available at
-- <a href="http://www.fmi.uni-passau.de/~groessli/hdoc">
-- www.fmi.uni-passau.de/~groessli/hdoc</a>
-- @version 0.3
module Countable where


---
-- For things that consist of countable components.
class Countable a where
    ---
    -- Counts the number of components.
    -- @param thing  -  the thing to count the components of.
    -- @return num   -  the number of components.
    count :: a -> Integer


---
-- Lists are countable objects.
-- Each element of the list is considered to be one component.
instance Countable [a] where
    ---
    -- Counts the components in a list.
    -- As &quot;one component&quot; is interpreted as
    -- &quot;one list element&quot;, the
    -- number of components in the list is equal to its length.
    --
    -- @param list  -  the list to count
    -- @return num  -  the number of elements in the list.
    count = fromInt . length