algorithm DrRacket Scheme parallel

module TreezDef where data BinaryTree = L | B BinaryTree BinaryTree deriving (Eq, Ord, Show) -- L = leaf, B = branch. The data constructor names are kept short for shorter -- printing outputs. -- "OBS" stands for "ordered by size". This is a wrapper type to select the Ord -- instance below. See below for what good this does. data OBS t = MkOBS t deriving (Eq, Show) -- Unwrapper. unOBS :: OBS t -> t unOBS (MkOBS a) = a -- This class is really just for the Ord (OBS t) instance below. class Sized t where size :: t -> Int -- we expect non-neg int -- If t is an Ord instance and also a Sized instance, then the Ord instance for -- the OBS wrapper compares by first comparing sizes, and only when tie, by t's -- own <=. instance (Ord t, Sized t) => Ord (OBS t) where MkOBS a1 <= MkOBS a2 = s1 < s2 || s1 == s2 && a1 <= a2 where s1 = size a1 s2 = size a2 -- Example: Strings are normally sorted alphabetically: -- "abbbbbb" < "ack" < "ask" -- If I want: Sort by length, and if two strings have the same length, then -- alphabetical order is OK: instance Sized [a] where size xs = length xs -- Then: MkOBS "ack" < MkOBS "ask" < MkOBS "abbbbbb".