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-rw-r--r--assignment-4/monad.dcl70
-rw-r--r--assignment-4/monad.icl16
-rw-r--r--assignment-4/serialize4.icl462
-rw-r--r--assignment-4/student.icl324
4 files changed, 445 insertions, 427 deletions
diff --git a/assignment-4/monad.dcl b/assignment-4/monad.dcl
index 6b0b2b5..531a191 100644
--- a/assignment-4/monad.dcl
+++ b/assignment-4/monad.dcl
@@ -1,35 +1,35 @@
-definition module monad
-
-/*
- Pieter Koopman, pieter@cs.ru.nl
- Advanced Programming, week 4
-*/
-
-import StdMisc
-
-class Functor f where
- fmap :: (a->b) (f a) -> (f b)
- (<$>) infixl 4 :: (a->b) (f a) -> (f b) | Functor f
- (<$>) f x :== fmap f x
-
-class Applicative f | Functor f where
- pure :: a -> f a
- (<*>) infixl 4 :: (f (a->b)) (f a) -> f b
-
-class Monad m | Applicative m where
- bind :: (m a) (a->m b) -> m b
- (>>=) infixl 1 :: (m a) (a->m b) -> m b | Monad m
- (>>=) a f :== bind a f
- (>>|) infixl 1 :: (m a) (m b) -> m b | Monad m
- (>>|) a b :== a >>= \_.b
- rtrn :: a -> m a | Monad m
- rtrn a :== pure a
-
-class fail m | Applicative m where
- fail :: m a
- guard :: Bool -> m a | fail m
- guard b :== if b (pure undef) fail
-
-class OrMonad m where
- (<|>) infixl 0 :: (m a) (m a) -> m a
-
+definition module monad
+
+/*
+ Pieter Koopman, pieter@cs.ru.nl
+ Advanced Programming, week 4
+*/
+
+import StdMisc
+
+class Functor f where
+ fmap :: (a->b) (f a) -> (f b)
+ (<$>) infixl 4 :: (a->b) (f a) -> (f b) | Functor f
+ (<$>) f x :== fmap f x
+
+class Applicative f | Functor f where
+ pure :: a -> f a
+ (<*>) infixl 4 :: (f (a->b)) (f a) -> f b
+
+class Monad m | Applicative m where
+ bind :: (m a) (a->m b) -> m b
+ (>>=) infixl 1 :: (m a) (a->m b) -> m b | Monad m
+ (>>=) a f :== bind a f
+ (>>|) infixl 1 :: (m a) (m b) -> m b | Monad m
+ (>>|) a b :== a >>= \_.b
+ rtrn :: a -> m a | Monad m
+ rtrn a :== pure a
+
+class fail m | Applicative m where
+ fail :: m a
+ guard :: Bool -> m a | fail m
+ guard b :== if b (pure undef) fail
+
+class OrMonad m where
+ (<|>) infixl 0 :: (m a) (m a) -> m a
+
diff --git a/assignment-4/monad.icl b/assignment-4/monad.icl
index fb9b491..bb0a2ac 100644
--- a/assignment-4/monad.icl
+++ b/assignment-4/monad.icl
@@ -1,8 +1,8 @@
-implementation module monad
-
-/*
- Pieter Koopman, pieter@cs.ru.nl
- Advanced Programming, week 4
-*/
-
-
+implementation module monad
+
+/*
+ Pieter Koopman, pieter@cs.ru.nl
+ Advanced Programming, week 4
+*/
+
+
diff --git a/assignment-4/serialize4.icl b/assignment-4/serialize4.icl
index edbcc32..9abccbc 100644
--- a/assignment-4/serialize4.icl
+++ b/assignment-4/serialize4.icl
@@ -1,231 +1,231 @@
-module serialize4
-
-import StdEnv, StdMaybe, monad
-
-/*
- * Pieter Koopman, pieter@cs.ru.nl
- * Advanced Programming, week 4, 2017
- *
- * import StdMaybe from Libraries/StdLib
- * use StdEnv or StdEnv 64
- * use Basic Values Only as conclose option for a nicer output.
- */
-
-// ---
-
-:: State s a = S (s -> (Maybe a,s))
-
-unS :: (State s a) -> s -> (Maybe a,s)
-unS (S f) = f
-
-instance Functor (State s) where
- fmap f s = fail
-instance Applicative (State s) where
- pure a = fail
- (<*>) f x = fail
-instance fail (State s) where
- fail = S \s.(Nothing,s)
-instance Monad (State s) where
- bind a f = fail
-instance OrMonad (State s) where
- (<|>) f g = fail
-
-// ---
-
-:: Serialized = Serialized
-
-ser :: Serialized
-ser = Serialized
-
-toStrings :: Serialized -> [String]
-toStrings _ = ["to be done\n"]
-
-:: Serialize a :== State Serialized a
-
-wrt :: a -> Serialize String | toString a
-wrt a = fail
-
-rd :: Serialize String
-rd = fail
-
-match :: a -> Serialize a | toString a
-match a = fail
-
-pred :: (String->Bool) -> Serialize String
-pred f = fail
-
-// ---
-
-:: UNIT = UNIT
-:: EITHER a b = LEFT a | RIGHT b
-:: PAIR a b = PAIR a b
-:: CONS a = CONS String a
-
-:: Write a :== a -> Serialize String
-:: Read a :== Serialize a
-
-class serialize a | isUNIT a where
- write :: a -> Serialize String
- read :: Serialize a
-
-class serialize1 t where
- write1 :: (Write a) (t a) -> Serialize String
- read1 :: (Read a) -> Serialize (t a)
-
-class serializeCONS a where
- writeCons :: (Write a) (CONS a) -> Serialize String
- readCons :: String (Read a) -> Serialize (CONS a)
-
-class serialize2 t where
- write2 :: (Write a) (Write b) (t a b) -> Serialize String
- read2 :: (Read a) (Read b) -> Serialize (t a b)
-
-class isUNIT a :: a -> Bool
-instance isUNIT UNIT where isUNIT _ = True
-instance isUNIT a where isUNIT _ = False
-
-instance serialize Bool where
- write b = fail
- read = fail
-
-instance serialize Int where
- write i = fail
- read = fail
-
-instance serialize String where
- write s = wrt s
- read = fail
-
-instance serialize UNIT where
- write _ = fail
- read = fail
-
-instance serializeCONS UNIT where
- writeCons wa (CONS name a) = fail
- readCons name ra = fail
-
-instance serializeCONS a where
- writeCons wa (CONS name a) = fail
- readCons name ra =fail
-
-instance serialize2 EITHER where
- write2 wa wb (LEFT a) = fail
- write2 wa wb (RIGHT b) = fail
- read2 ra rb = fail
-
-instance serialize2 PAIR where
- write2 wa wb (PAIR a b) = fail
- read2 ra rb = fail
-
-// ---
-
-:: 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 a = write1 write a
- read = read1 read
-
-instance serialize1 [] where
- write1 writea l = fail
- read1 reada = fail
-// ---
-
-:: 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 = fail
- read = fail
-
-instance serialize1 Bin where
- write1 writea b = fail
- read1 reada = fail
-// ---
-
-:: 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 = fail
- read = fail
-
-// ---
-
-instance serialize (a,b) | serialize a & serialize b where
- write (a,b) = fail
- read = fail
-
-// ---
-
-Start =
- [ test True
- , test False
- , test 0
- , test 123
- , test -36
- , test Head
- , test Tail
- , test [42]
- , test [0..4]
- , test [[True],[]]
- , test [[[1]],[[2],[3,4]],[[]]]
- , test [[True],[]]
- , 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 = toStrings (snd ((unS t) ser))
-where
- t = write a
- >>| read
- >>= \b. guard (a == b)
- >>| write "Oke "
- <|> write "Failure "
+module serialize4
+
+import StdEnv, StdMaybe, monad
+
+/*
+ * Pieter Koopman, pieter@cs.ru.nl
+ * Advanced Programming, week 4, 2017
+ *
+ * import StdMaybe from Libraries/StdLib
+ * use StdEnv or StdEnv 64
+ * use Basic Values Only as conclose option for a nicer output.
+ */
+
+// ---
+
+:: State s a = S (s -> (Maybe a,s))
+
+unS :: (State s a) -> s -> (Maybe a,s)
+unS (S f) = f
+
+instance Functor (State s) where
+ fmap f s = fail
+instance Applicative (State s) where
+ pure a = fail
+ (<*>) f x = fail
+instance fail (State s) where
+ fail = S \s.(Nothing,s)
+instance Monad (State s) where
+ bind a f = fail
+instance OrMonad (State s) where
+ (<|>) f g = fail
+
+// ---
+
+:: Serialized = Serialized
+
+ser :: Serialized
+ser = Serialized
+
+toStrings :: Serialized -> [String]
+toStrings _ = ["to be done\n"]
+
+:: Serialize a :== State Serialized a
+
+wrt :: a -> Serialize String | toString a
+wrt a = fail
+
+rd :: Serialize String
+rd = fail
+
+match :: a -> Serialize a | toString a
+match a = fail
+
+pred :: (String->Bool) -> Serialize String
+pred f = fail
+
+// ---
+
+:: UNIT = UNIT
+:: EITHER a b = LEFT a | RIGHT b
+:: PAIR a b = PAIR a b
+:: CONS a = CONS String a
+
+:: Write a :== a -> Serialize String
+:: Read a :== Serialize a
+
+class serialize a | isUNIT a where
+ write :: a -> Serialize String
+ read :: Serialize a
+
+class serialize1 t where
+ write1 :: (Write a) (t a) -> Serialize String
+ read1 :: (Read a) -> Serialize (t a)
+
+class serializeCONS a where
+ writeCons :: (Write a) (CONS a) -> Serialize String
+ readCons :: String (Read a) -> Serialize (CONS a)
+
+class serialize2 t where
+ write2 :: (Write a) (Write b) (t a b) -> Serialize String
+ read2 :: (Read a) (Read b) -> Serialize (t a b)
+
+class isUNIT a :: a -> Bool
+instance isUNIT UNIT where isUNIT _ = True
+instance isUNIT a where isUNIT _ = False
+
+instance serialize Bool where
+ write b = fail
+ read = fail
+
+instance serialize Int where
+ write i = fail
+ read = fail
+
+instance serialize String where
+ write s = wrt s
+ read = fail
+
+instance serialize UNIT where
+ write _ = fail
+ read = fail
+
+instance serializeCONS UNIT where
+ writeCons wa (CONS name a) = fail
+ readCons name ra = fail
+
+instance serializeCONS a where
+ writeCons wa (CONS name a) = fail
+ readCons name ra =fail
+
+instance serialize2 EITHER where
+ write2 wa wb (LEFT a) = fail
+ write2 wa wb (RIGHT b) = fail
+ read2 ra rb = fail
+
+instance serialize2 PAIR where
+ write2 wa wb (PAIR a b) = fail
+ read2 ra rb = fail
+
+// ---
+
+:: 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 a = write1 write a
+ read = read1 read
+
+instance serialize1 [] where
+ write1 writea l = fail
+ read1 reada = fail
+// ---
+
+:: 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 = fail
+ read = fail
+
+instance serialize1 Bin where
+ write1 writea b = fail
+ read1 reada = fail
+// ---
+
+:: 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 = fail
+ read = fail
+
+// ---
+
+instance serialize (a,b) | serialize a & serialize b where
+ write (a,b) = fail
+ read = fail
+
+// ---
+
+Start =
+ [ test True
+ , test False
+ , test 0
+ , test 123
+ , test -36
+ , test Head
+ , test Tail
+ , test [42]
+ , test [0..4]
+ , test [[True],[]]
+ , test [[[1]],[[2],[3,4]],[[]]]
+ , test [[True],[]]
+ , 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 = toStrings (snd ((unS t) ser))
+where
+ t = write a
+ >>| read
+ >>= \b. guard (a == b)
+ >>| write "Oke "
+ <|> write "Failure "
diff --git a/assignment-4/student.icl b/assignment-4/student.icl
index 0356a04..96c01e0 100644
--- a/assignment-4/student.icl
+++ b/assignment-4/student.icl
@@ -1,153 +1,171 @@
-module student
-
-import StdEnv, StdMaybe, monad
-/*
- * Pieter Koopman, pieter@cs.ru.nl
- * Advanced Programming, week 4
- */
-
-// ---- an IO monad with maybe results --- //
-
-:: *State = {w :: *World, c :: *Maybe *File}
-:: IO a = IO (State -> *(Maybe a, State))
-
-open :: State -> State
-open {w, c=Nothing}
- # (console, w) = stdio w
- = {w = w, c = Just console}
-open s = s
-
-close :: State -> State
-close { w, c=Just f} = { w = snd (fclose f w), c = Nothing}
-close s = s
-
-unIO :: (IO a) -> State -> *(Maybe a, State)
-unIO (IO f) = f
-
-run :: (IO a) *World -> *World
-run m w = (close (snd (unIO m {w=w, c=Nothing}))).w
-
-// ---- reading from console --- //
-
-class read a :: IO a
-
-instance read String where
- read = IO r where
- r s
- #! {w,c=Just c} = open s
- (line, c) = freadline c
- s = rmNL line
- | size s > 0
- = (Just s,{w = w, c = Just c})
- #! c = c <<< "String must be not empty "
- (line, c) = freadline c
- s = rmNL line
- | size s > 0
- = (Just s, {w = w, c = Just c})
- = (Nothing, {w = w, c = Just c})
-
-instance read Int where
- read = IO r where
- r s
- #! {w,c=Just c} = open s
- (b,i,c) = freadi c
- | b
- = (Just i, {w = w, c = Just c})
- #! (_, c) = freadline c
- c = c <<< "An integer please "
- (b,i,c) = freadi c
- | b
- = (Just i, {w = w, c = Just c})
- #! (_, c) = freadline c
- = (Nothing, {w = w, c = Just c})
-
-write :: String -> IO String
-write mess = IO w where
- w s
- #! {w,c=Just c} = open s
- = (Just mess,{w=w,c=Just (c <<< mess)})
-
-// ---- make IO a monad --- //
-
-instance Functor IO where
- fmap f (IO g)
- = IO \s.case g s of
- (Just a, s) = (Just (f a),s)
- (Nothing,s) = (Nothing , s)
-
-instance Applicative IO where
- pure a = IO \s.(Just a, s)
- (<*>) (IO f) (IO g) = IO \s.case f s of
- (Just f,s) = case g s of
- (Just a,s) = (Just (f a),s)
- (n, s) = (Nothing, s)
- (n, s) = (Nothing, s)
-
-instance Monad IO where
- bind (IO f) g = IO \s.case f s of
- (Just a, s) = unIO (g a) s
- (n, s) = (Nothing, s)
-
-instance fail IO where fail = IO \s.(Nothing,s)
-
-instance OrMonad IO where
- <|> (IO f) (IO g) =
- IO \s.case f s of
- (Nothing, s) = g s
- other = other
-
-// ---- reading a student record --- //
-
-Start w = run f2 w
-
-:: Student =
- { fname :: String
- , lname :: String
- , snum :: Int
- }
-
-instance toString Student where
- toString {fname,lname,snum} = "{Student|fname=" + fname + ",lname=" + lname + ",snum=" + toString snum + "}"
-instance + String where + s t = s +++ t
-
-f0 :: *World -> (Student, *World)
-f0 world = ({fname = rmNL fname, lname = rmNL lname, snum = snum}, world2) where
- (console1, world1) = stdio world
- console2 = console1 <<< "Your first name please: "
- (fname,console3) = freadline console2
- console4 = console3 <<< "Your last name please: "
- (lname,console5) = freadline console4
- console6 = console5 <<< "Your student nmber please: "
- (b1,snum,console7) = freadi console6
- (b2, world2) = fclose console7 world1
-
-f1 :: *World -> (Student, *World)
-f1 world
-#! (console, world) = stdio world
- console = console <<< "Your first name please: "
- (fname,console) = freadline console
- console = console <<< "Your last name please: "
- (lname,console) = freadline console
- console = console <<< "Your student nmber please: "
- (b1,snum,console) = freadi console
- (b2, world) = fclose console world
-= ({fname = rmNL fname, lname = rmNL lname, snum = snum}, world)
-
-f2 :: IO String
-f2
- = ( write "Your first name please: "
- >>| read
- >>= \fname.write "Your last name please: "
- >>| read
- >>= \lname.write "Your student nmber please: "
- >>| read
- >>= \snum. rtrn {fname = rmNL fname, lname = rmNL lname, snum = snum}
- >>= write o toString)
- <|> write "failed to read a student"
-
-rmNL :: String -> String
-rmNL string
- # len = size string
- | len > 0 && string.[len-1] == '\n'
- = string % (0, len - 2)
- = string
+module student
+
+import StdEnv, StdMaybe, monad
+/*
+ * Pieter Koopman, pieter@cs.ru.nl
+ * Advanced Programming, week 4
+ */
+
+// ---- an IO monad with maybe results --- //
+
+:: *State = {w :: *World, c :: *Maybe *File}
+:: IO a = IO (State -> *(Maybe a, State))
+
+open :: State -> State
+open {w, c=Nothing}
+ # (console, w) = stdio w
+ = {w = w, c = Just console}
+open s = s
+
+close :: State -> State
+close { w, c=Just f} = { w = snd (fclose f w), c = Nothing}
+close s = s
+
+unIO :: (IO a) -> State -> *(Maybe a, State)
+unIO (IO f) = f
+
+run :: (IO a) *World -> *World
+run m w = (close (snd (unIO m {w=w, c=Nothing}))).w
+
+// ---- reading from console --- //
+
+class read a :: IO a
+
+instance read String where
+ read = IO r where
+ r s
+ #! {w,c=Just c} = open s
+ (line, c) = freadline c
+ s = rmNL line
+ | size s > 0
+ = (Just s,{w = w, c = Just c})
+ #! c = c <<< "String must be not empty "
+ (line, c) = freadline c
+ s = rmNL line
+ | size s > 0
+ = (Just s, {w = w, c = Just c})
+ = (Nothing, {w = w, c = Just c})
+
+instance read Int where
+ read = IO r where
+ r s
+ #! {w,c=Just c} = open s
+ (b,i,c) = freadi c
+ | b
+ = (Just i, {w = w, c = Just c})
+ #! (_, c) = freadline c
+ c = c <<< "An integer please "
+ (b,i,c) = freadi c
+ | b
+ = (Just i, {w = w, c = Just c})
+ #! (_, c) = freadline c
+ = (Nothing, {w = w, c = Just c})
+
+write :: String -> IO String
+write mess = IO w where
+ w s
+ #! {w,c=Just c} = open s
+ = (Just mess,{w=w,c=Just (c <<< mess)})
+
+// ---- make IO a monad --- //
+
+instance Functor IO where
+ fmap f (IO g)
+ = IO \s.case g s of
+ (Just a, s) = (Just (f a),s)
+ (Nothing,s) = (Nothing , s)
+
+instance Applicative IO where
+ pure a = IO \s.(Just a, s)
+ (<*>) (IO f) (IO g) = IO \s.case f s of
+ (Just f,s) = case g s of
+ (Just a,s) = (Just (f a),s)
+ (n, s) = (Nothing, s)
+ (n, s) = (Nothing, s)
+
+instance Monad IO where
+ bind (IO f) g = IO \s.case f s of
+ (Just a, s) = unIO (g a) s
+ (n, s) = (Nothing, s)
+
+instance fail IO where fail = IO \s.(Nothing,s)
+
+instance OrMonad IO where
+ <|> (IO f) (IO g) =
+ IO \s.case f s of
+ (Nothing, s) = g s
+ other = other
+
+// ---- reading a student record --- //
+
+Start w = run (f3 >>= write) w
+
+:: Student =
+ { fname :: String
+ , lname :: String
+ , snum :: Int
+ }
+
+instance toString Student where
+ toString {fname,lname,snum} = "{Student|fname=" + fname + ",lname=" + lname + ",snum=" + toString snum + "}"
+instance + String where + s t = s +++ t
+
+f0 :: *World -> (Student, *World)
+f0 world = ({fname = rmNL fname, lname = rmNL lname, snum = snum}, world2) where
+ (console1, world1) = stdio world
+ console2 = console1 <<< "Your first name please: "
+ (fname,console3) = freadline console2
+ console4 = console3 <<< "Your last name please: "
+ (lname,console5) = freadline console4
+ console6 = console5 <<< "Your student nmber please: "
+ (b1,snum,console7) = freadi console6
+ (b2, world2) = fclose console7 world1
+
+f1 :: *World -> (Student, *World)
+f1 world
+#! (console, world) = stdio world
+ console = console <<< "Your first name please: "
+ (fname,console) = freadline console
+ console = console <<< "Your last name please: "
+ (lname,console) = freadline console
+ console = console <<< "Your student nmber please: "
+ (b1,snum,console) = freadi console
+ (b2, world) = fclose console world
+= ({fname = rmNL fname, lname = rmNL lname, snum = snum}, world)
+
+f2 :: IO String
+f2
+ = ( write "Your first name please: "
+ >>| read
+ >>= \fname.write "Your last name please: "
+ >>| read
+ >>= \lname.write "Your student nmber please: "
+ >>| read
+ >>= \snum. rtrn {fname = rmNL fname, lname = rmNL lname, snum = snum}
+ >>= write o toString)
+ <|> write "failed to read a student"
+
+f3 :: IO String
+f3 =
+ ((\f l s -> (toString {fname=rmNL f, lname=rmNL l, snum=s}) +++ "\n") <$>
+ input "Your first name please: " <*>
+ input "Your last name please: " <*>
+ input "Your student number please: ")
+ <|> write "Failed to read a student.\n"
+where
+ input :: String -> IO a | read a
+ input s = write s *> read
+
+ // It would really be much easier if we would use Platform from the start in this course.
+ (*>) infixl 4 :: (f a) (f b) -> f b | Applicative f
+ (*>) fa fb = id <$ fa <*> fb
+
+ (<$) infixl 4 :: a (f b) -> f a | Functor f
+ (<$) x fa = fmap (const x) fa
+
+rmNL :: String -> String
+rmNL string
+ # len = size string
+ | len > 0 && string.[len-1] == '\n'
+ = string % (0, len - 2)
+ = string
generated by cgit v1.2.3 (git 2.39.1) at 2025-07-01 19:15:10 +0000