-- a function does not have to be defined in terms of specific data types. The defintion acts to 
-- constrain how a function can act, and allow Haskell to reason about your program. As such, it may
-- not matter exactly what the data type is, as long as it obeys some constraints.

-- Lists provide a good example
function1 :: [a]->([a],[a])
function1 (x:xs) = ([x],xs)

-- this takes a list of things, and returns a tuple of 2 lists OF THE SAME THINGS.

-- the one definition you cannot use is a->b
-- this would imply a something to something else, which while probably quite accurate is also to
-- unconstrained as to be pointless.  

-- for generality most functions are actually defined in terms of type variables rather than 
-- specific data types.