ref: b2de98441112c9eac3de6d7d43537fed2dc66855
dir: /tests/Record.hs/
module Record(main) where
import Prelude
-- HasField instances are derived automatically
data R = CR { a :: Int, b :: Bool }
instance Show R where
show (CR a b) = "R{a=" ++ show a ++ ",b=" ++ show b ++ "}"
data RR = CRR { r :: R, a :: Bool }
r1 :: R
r1 = CR { a=1, b=True }
r2 :: R
r2 = CR { b=True, a=2 }
r3 :: R
r3 = CR { b=True }
--r4 :: R
--r4 = R { c=True }
r5 :: R
r5 = r1 { a = (10::Int) }
r6 :: R
r6 = r1 { a = (10::Int), b=False }
rr1 :: RR
rr1 = CRR { r = r1, a = True }
sel_a :: forall r t . HasField "a" r t => r -> t
sel_a = (.a)
data S a = S1 { x :: Int } | S2 { x :: Int, y :: a }
instance forall a . Show a => Show (S a) where
show (S1 x) = "S1 " ++ show x
show (S2 x y) = "S2 " ++ show x ++ " " ++ show y
s1 :: S Bool
s1 = S1 10
s2 :: S String
s2 = S2 { x = 20, y = "foo" }
main :: IO ()
main = do
print r1
print r2
-- print r3
print r5
print r6
print $ r2.a
print $ r2.b
print $ rr1.r.a
print $ rr1.a
print $ (.a) r1
print $ sel_a r1
print $ sel_a rr1
print s1
print s2
print s1{x=99}
print s2{x=88}
print s2{y="bar"}