ref: bdd38072a2fa4108fff41da806309074e79ce6de
dir: /tests/PatSyn.hs/
module PatSyn where
import PatSynE
f1 :: [a] -> (a, [a])
f1 (Sings a as) = (a, as)
f2 :: [a] -> a
f2 (Sing a) = a
pattern Dup :: Eq a => a -> [a]
pattern Dup a <- (dup -> (Just a))
where Dup a = [a, a]
dup :: (Eq a) => [a] -> Maybe a
dup [x,x'] | x==x' = Just x
dup _ = Nothing
f3 :: [Int] -> Int
f3 (Dup x) = x
f3 _ = 0
f4 :: Int -> Int
f4 One = 99
f4 _ = 88
data S b = forall a . Show a => S (a,b)
instance Show b => Show (S b) where
show (S xy) = show xy
pattern SP :: () => Show a => a -> S Bool
pattern SP a = S (a, True)
f5 :: S Bool -> String
f5 (SP x) = show x
ss :: S Bool
ss = S ((), True)
----
data T a = forall b . Show b => MkT a b
pattern ExNumPat1 :: (Num a, Eq a) => (Show b) => b -> T a
pattern ExNumPat1 x = MkT 42 x
pattern ExNumPat2 x = MkT 42 x
ft1 :: (Eq a, Num a) => T a -> String
ft1 (ExNumPat1 x) = show x
ft2 :: (Eq a, Num a) => T a -> String
ft2 (ExNumPat2 x) = show x
main :: IO ()
main = do
print $ Sing 1
print $ Swap 1 2
print $ f1 [3]
print $ f2 [4]
-- print (Sings 1 [2]) this is an error, of course
print (Dup 22)
print $ f3 [11,11]
print $ f3 [11,12]
print (One :: Int)
print (One :: Double)
print $ f4 1
print $ f4 2
print $ SP ()
print $ f5 ss
let x = MkT 42 True
y = ExNumPat1 ()
z = ExNumPat2 ()
print (ft1 x, ft2 x)
print (ft1 y, ft2 y)
print (ft1 z, ft2 z)
print AA
case A of AA -> print 42