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{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE AllowAmbiguousTypes #-}
module T14955a where
import Prelude (Bool(..), (||), (&&))
-- Implementation 1
class Prop r where
or :: r -> r -> r
and :: r -> r -> r
true :: r
false :: r
instance Prop Bool where
or = (||)
and = (&&)
true = True
false = False
-- Implementation 2
data PropDict r = PropDict {
dor :: r -> r -> r
, dand :: r -> r -> r
, dtrue :: r
, dfalse :: r
}
boolDict = PropDict {
dor = (||)
, dand = (&&)
, dtrue = True
, dfalse = False }
-- Implementation 3
class PropProxy r where
propDict :: PropDict r
instance PropProxy Bool where
propDict = boolDict
-- Implementation 4
class PropProxy2 r where
propDict2 :: PropDict r
dummy :: ()
instance PropProxy2 Bool where
propDict2 = boolDict
dummy = ()
ors :: Prop r => [r] -> r
ors [] = true
ors (o:os) = o `or` ors os
{-# INLINABLE ors #-}
dors :: PropDict r -> [r] -> r
dors pd [] = dtrue pd
dors pd (o:os) = dor pd o (dors pd os)
pors :: PropProxy r => [r] -> r
pors [] = dtrue propDict
pors (o:os) = dor propDict o (pors os)
{-# INLINABLE pors #-}
porsProxy :: PropProxy2 r => [r] -> r
porsProxy [] = dtrue propDict2
porsProxy (o:os) = dor propDict2 o (porsProxy os)
{-# INLINABLE porsProxy #-}
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