gistfile1.hs

module Main where
  -- Q1. Write a function that looks up a hash table value that uses the Maybe Monad. (IMHO this 
  -- question is kinda sloppily written, does the hash table use the maybe monad or the function?).
  -- Write a hash that stores other hashes, several levels deep. Use the Maybe monad to retrieve 
  -- an element several levels deep. (wtf does this even mean? is the maybe monad going to do the 
  -- retrieving for me?)
  
  -- What I am going to attempt to do (my interpretation of the above):
  --  1. Write a function that looks up a value by key (in a collection of key value pairs)
  --     and returns a result wrapped in the Maybe monad. 
  --  2. Write a function that can look for a value in a list of (posibly) nested key-value pair collections
  --     returning results wrapped in a maybe
  --  Note: I do know that haskell has a Data.Map type, i am just assuming we are not supposed to use
  --  it for pedagogical reasons.
  
  hash = [('a', "apple"), ('b', "bear"), ('c', "cat"), ('d', "dog")]
  
  find :: Eq a => [(a, b)] -> a ->  Maybe b
  find [] _ = Nothing
  find tuples key = let
    (nextKey, nextVal) = head tuples
    rest = tail tuples
    in
      if key == nextKey then Just nextVal else find rest key