[SOLVED] CS代考程序代写 Haskell {-

{-
Module: StateTreeInstances.

Used by quickcheck in the tests.
-}
module Util.StateTreeInstances where

import Test.QuickCheck
import Control.Monad

import Types

— Generate an arbitrary state tree.
arbitraryTree :: (Arbitrary v, Arbitrary a) => Int -> Gen (StateTree v a)
arbitraryTree 0 = do
x <- arbitrary return (StateTree x [])arbitraryTree n = do m <- arbitrary let n’ = n `div` (m + 1)x <- arbitraryas <- replicateM m arbitraryts <- replicateM m (arbitraryTree n’)return (StateTree x (zip as ts))– Tell Haskell that we can generate arbitrary state trees.instance (Arbitrary v, Arbitrary a) => Arbitrary (StateTree v a) where
arbitrary = sized arbitraryTree

— Describes how state trees are printed.
instance (Show v, Show a) => Show (StateTree v a) where
show (StateTree v ts) = “(StateTree ” ++ (show v) ++ ” ” ++ (show ts) ++ “)”