== API ==
-- functions --
(:) :: Int -> [Int] -> [Int]
(++) :: [Int] -> [Int] -> [Int]
head :: [Int] -> Int
tail :: [Int] -> [Int]
[] :: [Int]

-- variables --
x, y, z :: Int
xs, ys, zs :: [Int]

== Testing ==
Depth 1: 9 terms, 3 tests, 18 evaluations, 9 classes, 0 raw equations.
Depth 2: 45 terms, 500 tests, 7585 evaluations, 36 classes, 9 raw equations.
Depth 3: 1017 terms, 500 tests, 182341 evaluations, 795 classes, 222 raw equations.
Depth 4: 4575 terms, 500 tests, 1724824 evaluations, 2316 classes, 2259 raw equations.
2259 raw equations; 2316 terms in universe.

== Equations about (++) ==
  1: xs++[] == xs
  2: []++xs == xs
  3: (xs++ys)++zs == xs++(ys++zs)

== Equations about head ==
  4: head [] == undefined

== Equations about tail ==
  5: tail [] == undefined

== Equations about several functions ==
  6: (x:xs)++ys == x:(xs++ys)
  7: head (x:xs) == x
  8: tail (x:xs) == xs
  9: head (xs++xs) == head xs
 10: tail xs++xs == tail (xs++xs)
 11: head (xs++(x:ys)) == head (xs++(x:zs))
 12: head (xs++(xs++ys)) == head (xs++ys)
 13: head (xs++(ys++xs)) == head (xs++ys)
 14: head (xs++(ys++ys)) == head (xs++ys)
 15: tail (xs++ys)++xs == tail (xs++(ys++xs))
 16: tail (xs++ys)++ys == tail (xs++(ys++ys))
 17: head (xs++tail xs) == head xs
 18: tail (xs++tail xs) == tail xs++tail xs
 19: head ((x:xs)++tail ys) == x
 20: tail ((x:xs)++tail ys) == xs++tail ys
 21: head ((xs++ys)++tail xs) == head (xs++ys)
 22: head ((xs++ys)++tail ys) == head (xs++ys)
 23: head (tail xs++(xs++ys)) == head (tail (xs++xs))
 24: head xs:(tail xs++ys) == head xs:tail (xs++ys)
 25: tail xs++(tail xs++ys) == tail xs++tail (xs++ys)
 26: tail (xs++ys)++tail xs == tail ((xs++ys)++tail xs)
 27: tail (xs++ys)++tail ys == tail ((xs++ys)++tail ys)
 28: head xs:tail (xs++xs) == xs++(head xs:tail xs)