max expr size  =    5
  |- on ineqs  =    4
  |- on conds  =    4
max  #-tests   =  500
min  #-tests   =   25  (to consider p ==> q true)
max  #-vars    =    2  (for inequational and conditional laws)

_ :: Bool
_ :: Int
_ :: [Int]
[] :: [Int]
(:) :: Int -> [Int] -> [Int]
insert :: Int -> [Int] -> [Int]
sort :: [Int] -> [Int]
(<=) :: Int -> Int -> Bool
(<) :: Int -> Int -> Bool
True :: Bool
False :: Bool
(==) :: Bool -> Bool -> Bool
(==) :: Int -> Int -> Bool
(==) :: [Int] -> [Int] -> Bool

   (xs == insert x xs) == False
   ([] == insert x xs) == False
       (sort xs == []) == (xs == [])
               sort [] == []
        sort (sort xs) == sort xs
           insert x [] == [x]
    sort (insert x xs) == insert x (sort xs)
           sort (x:xs) == insert x (sort xs)
insert x (insert y xs) == insert y (insert x xs)
       insert x (x:xs) == x:x:xs
          insert x [y] == insert y [x]

x <= y ==> insert x (y:xs) == x:y:xs
 x < y ==> insert y (x:xs) == x:insert y xs