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module serialize3Start
/*
Definitions for assignment 3 in AFP 2017
Kind indexed gennerics
Pieter Koopman, pieter@cs.ru.nl
September 2017
use environment: StdMaybe from Libraries/StdLib
*/
import StdEnv, StdMaybe
:: Write a :== a [String] -> [String]
:: Read a :== [String] -> Maybe (a,[String])
// use this as serialize0 for kind *
class serialize a
where
write :: a [String] -> [String]
read :: [String] -> Maybe (a,[String])
class serialize1 t
where
write1 :: (Write a) (t a) [String] -> [String]
read1 :: (Read a) [String] -> Maybe (t a, [String])
class serialize2 t
where
write2 :: (Write a) (Write b) (t a b) [String] -> [String]
read2 :: (Read a) (Read b) [String] -> Maybe (t a b, [String])
// ---
instance serialize Bool where
write b c = [toString b:c]
read ["True":r] = Just (True,r)
read ["False":r] = Just (False,r)
read _ = Nothing
instance serialize Int where
write i c = [toString i:c]
read [s:r]
# i = toInt s
| s == toString i
= Just (i,r)
= Nothing
read _ = Nothing
// ---
:: UNIT = UNIT
:: EITHER a b = LEFT a | RIGHT b
:: PAIR a b = PAIR a b
:: CONS a = CONS String a
instance serialize UNIT
where
write UNIT s = s
read l = Just (UNIT, l)
instance serialize2 EITHER
where
write2 f _ (LEFT x) s = f x s
write2 _ g (RIGHT x) s = g x s
read2 f g s = case f s of
Just (x,s) -> Just (LEFT x,s)
Nothing -> case g s of
Just (x,s) -> Just (RIGHT x,s)
Nothing -> Nothing
instance serialize2 PAIR
where
write2 f g (PAIR x y) s = f x [" ":g y s]
read2 f g s = case f s of
Just (x,[" ":s]) -> case g s of
Just (y,s) -> Just (PAIR x y,s)
Nothing -> Nothing
_ -> Nothing
instance serialize1 CONS
where
write1 f (CONS c x) s = cleanup ["(":c:" ":f x [")":s]]
where
// Remove redundant parentheses
cleanup :: [String] -> [String]
cleanup ["(":c:" ":")":s] = [c:s]
cleanup s = s
read1 _ _ = abort "Use read1Cons instead\n"
/**
* Special read1 variant which checks for a constructor name.
* @param The constructor name to match
* @param The read function for the constructor argument
* @param The stream
* @result The parsed constructor and the rest of the stream, if successful
*/
read1Cons :: String (Read a) [String] -> Maybe (CONS a, [String])
read1Cons n f ["(":c:" ":s]
| c == n = case f s of
Just (x,[")":s]) -> Just (CONS c x,s)
_ -> Nothing
| otherwise = Nothing
// Special case for constructors without parentheses. After reading the
// argument, we continue with the original stream, because cleanup only removes
// parentheses for constructors where the write of the argument did not write
// anything. It is probably equivalent to continuing with the new stream (as
// the read should not read anything), but this seems safer.
read1Cons n f [c:s]
| c == n = case f s of
Just (x,_) -> Just (CONS c x,s)
Nothing -> Nothing
| otherwise = Nothing
read1Cons _ _ _ = Nothing
// ---
:: ListG a :== EITHER (CONS UNIT) (CONS (PAIR a [a]))
fromList :: [a] -> ListG a
fromList [] = LEFT (CONS NilString UNIT)
fromList [a:x] = RIGHT (CONS ConsString (PAIR a x))
toList :: (ListG a) -> [a]
toList (LEFT (CONS NilString UNIT)) = []
toList (RIGHT (CONS ConsString (PAIR a x))) = [a:x]
NilString :== "Nil"
ConsString :== "Cons"
instance serialize [a] | serialize a
where
write xs s = write2 (write1 write) (write1 (write2 write write)) (fromList xs) s
read s = case read2 (read1Cons NilString read) (read1Cons ConsString (read2 read read)) s of
Just (xs,s) -> Just (toList xs,s)
Nothing -> Nothing
// ---
:: Bin a = Leaf | Bin (Bin a) a (Bin a)
:: BinG a :== EITHER (CONS UNIT) (CONS (PAIR (Bin a) (PAIR a (Bin a))))
fromBin :: (Bin a) -> BinG a
fromBin Leaf = LEFT (CONS LeafString UNIT)
fromBin (Bin l a r) = RIGHT (CONS BinString (PAIR l (PAIR a r)))
toBin :: (BinG a) -> Bin a
toBin (LEFT (CONS _ UNIT)) = Leaf
toBin (RIGHT (CONS _ (PAIR l (PAIR a r)))) = Bin l a r
LeafString :== "Leaf"
BinString :== "Bin"
instance == (Bin a) | == a where
(==) Leaf Leaf = True
(==) (Bin l a r) (Bin k b s) = l == k && a == b && r == s
(==) _ _ = False
instance serialize (Bin a) | serialize a where
write b s = write2 (write1 write) (write1 (write2 write (write2 write write))) (fromBin b) s
read l = case read2 (read1Cons LeafString read) (read1Cons BinString (read2 read (read2 read read))) l of
Just (b,s) -> Just (toBin b,s)
Nothing -> Nothing
// ---
:: Coin = Head | Tail
:: CoinG :== EITHER (CONS UNIT) (CONS UNIT)
fromCoin :: Coin -> CoinG
fromCoin Head = LEFT (CONS "Head" UNIT)
fromCoin Tail = RIGHT (CONS "Tail" UNIT)
toCoin :: CoinG -> Coin
toCoin (LEFT (CONS _ UNIT)) = Head
toCoin (RIGHT (CONS _ UNIT)) = Tail
instance == Coin where
(==) Head Head = True
(==) Tail Tail = True
(==) _ _ = False
instance serialize Coin where
write c s = write2 (write1 write) (write1 write) (fromCoin c) s
read l = case read2 (read1Cons "Head" read) (read1Cons "Tail" read) l of
Just (c,l) -> Just (toCoin c,l)
Nothing -> Nothing
/*
Define a special purpose version for this type that writes and reads
the value (7,True) as ["(","7",",","True",")"]
*/
instance serialize (a,b) | serialize a & serialize b where
write t c = write2 write write t c
read l = read2 read read l
instance serialize2 (,)
where
write2 f g (x,y) s = ["(":f x [",":g y [")":s]]]
read2 f g ["(":s] = case f s of
Just (x,[",":s]) -> case g s of
Just (y,[")":s]) -> Just ((x,y), s)
_ -> Nothing
_ -> Nothing
read2 _ _ _ = Nothing
// ---
// output looks nice if compiled with "Basic Values Only" for console in project options
Start =
[test True
,test False
,test 0
,test 123
,test -36
,test [42]
,test [0..4]
,test [[True],[]]
,test [[[1]],[[2],[3,4]],[[]]]
,test (Bin Leaf True Leaf)
,test [Bin (Bin Leaf [1] Leaf) [2] (Bin Leaf [3] (Bin Leaf [4,5] Leaf))]
,test [Bin (Bin Leaf [1] Leaf) [2] (Bin Leaf [3] (Bin (Bin Leaf [4,5] Leaf) [6,7] (Bin Leaf [8,9] Leaf)))]
,test Head
,test Tail
,test (7,True)
,test (Head,(7,[Tail]))
,["End of the tests.\n"]
]
test :: a -> [String] | serialize, == a
test a =
(if (isJust r)
(if (fst jr == a)
(if (isEmpty (tl (snd jr)))
["Oke"]
["Not all input is consumed! ":snd jr])
["Wrong result: ":write (fst jr) []])
["read result is Nothing"]
) ++ [", write produces: ": s]
where
s = write a ["\n"]
r = read s
jr = fromJust r
/*
Oke, write produces: True
Oke, write produces: False
Oke, write produces: 0
Oke, write produces: 123
Oke, write produces: -36
Oke, write produces: (Cons 42 Nil)
Oke, write produces: (Cons 0 (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil)))))
Oke, write produces: (Cons (Cons True Nil) (Cons Nil Nil))
Oke, write produces: (Cons (Cons (Cons 1 Nil) Nil) (Cons (Cons (Cons 2 Nil) (Cons (Cons 3 (Cons 4 Nil)) Nil)) (Cons (Cons Nil Nil) Nil)))
Oke, write produces: (Bin Leaf True Leaf)
Oke, write produces: (Cons (Bin (Bin Leaf (Cons 1 Nil) Leaf) (Cons 2 Nil) (Bin Leaf (Cons 3 Nil) (Bin Leaf (Cons 4 (Cons 5 Nil)) Leaf))) Nil)
Oke, write produces: (Cons (Bin (Bin Leaf (Cons 1 Nil) Leaf) (Cons 2 Nil) (Bin Leaf (Cons 3 Nil) (Bin (Bin Leaf (Cons 4 (Cons 5 Nil)) Leaf) (Cons 6 (Cons 7 Nil)) (Bin Leaf (Cons 8 (Cons 9 Nil)) Leaf)))) Nil)
Oke, write produces: Head
Oke, write produces: Tail
Oke, write produces: (7,True)
Oke, write produces: (Head,(7,(Cons Tail Nil)))
End of the tests.
*/
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