Difference between revisions of "PropLang"
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NeilMitchell (talk | contribs) |
NeilMitchell (talk | contribs) |
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data Var a = ... |
data Var a = ... |
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− | data Notify |
+ | data Notify = ... |
get :: Var a -> IO a |
get :: Var a -> IO a |
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newVar :: a -> IO (Var a) |
newVar :: a -> IO (Var a) |
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+ | |||
+ | == A concrete implementation of Var == |
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+ | |||
+ | One thing to avoid, global state that needs a specific init function |
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+ | |||
+ | data Var a = Var {value :: IORef a, |
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+ | notifyId :: IORef Integer, |
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+ | notifys :: IORef [(Integer, a -> IO ())], |
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+ | source :: IORef (Maybe (Action a))} |
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+ | |||
+ | data Notify = Notify {notifyId :: Integer, notifys :: IORef [(Integer, a -> IO ())]} |
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+ | |||
+ | newVar :: a -> IO (Var a) |
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+ | newVar x = do v <- newIORef x |
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+ | n <- newIORef [] |
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+ | c <- newIORef 0 |
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+ | a <- newIORef Nothing |
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+ | return $ Var v c n a |
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+ | |||
+ | get :: Var a -> IO a |
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+ | get var = readIORef (value var) |
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+ | |||
+ | set :: Var a -> a -> IO () |
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+ | set var x = do n <- readIORef (notifys var) |
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+ | writeIORef (value var) x |
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+ | mapM_ (\(a,b) -> b x) n |
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+ | |||
+ | addNotify :: Var a -> (a -> IO ()) -> IO Notify |
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+ | addNotify var f = do n <- readIORef (notifys var) |
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+ | c <- readIORef (notifyId var) |
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+ | writeIORef (notifyId var) (c+1) |
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+ | writeIORef (notifys var) ((c, f) : n) |
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+ | return $ Notify c (notifys var) |
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+ | |||
+ | remNotify :: Notify -> IO () |
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+ | remNotify notify = do n <- readIORef (notifys notify) |
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+ | writeIORef (notifys notify) (filter (\x -> fst x /= notifyId notify) n) |
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== Object layering == |
== Object layering == |
Revision as of 14:34, 18 July 2006
A design for a GUI library which is more like Haskell and less like C. To be written over Gtk2Hs.
Link: http://www.cse.unsw.edu.au/~chak/haskell/ports/
Thoughts by
Neil Mitchell, Duncan Coutts
The Var concept
This is the low level stuff, on which the library will be built
data Var a = ... data Notify = ...
get :: Var a -> IO a set :: Var a -> a -> IO () addNotify :: Var a -> (a -> IO ()) -> IO Notify remNotify :: Notify -> IO ()
newVar :: a -> IO (Var a)
A concrete implementation of Var
One thing to avoid, global state that needs a specific init function
data Var a = Var {value :: IORef a, notifyId :: IORef Integer, notifys :: IORef [(Integer, a -> IO ())], source :: IORef (Maybe (Action a))}
data Notify = Notify {notifyId :: Integer, notifys :: IORef [(Integer, a -> IO ())]}
newVar :: a -> IO (Var a) newVar x = do v <- newIORef x n <- newIORef [] c <- newIORef 0 a <- newIORef Nothing return $ Var v c n a
get :: Var a -> IO a get var = readIORef (value var)
set :: Var a -> a -> IO () set var x = do n <- readIORef (notifys var) writeIORef (value var) x mapM_ (\(a,b) -> b x) n
addNotify :: Var a -> (a -> IO ()) -> IO Notify addNotify var f = do n <- readIORef (notifys var) c <- readIORef (notifyId var) writeIORef (notifyId var) (c+1) writeIORef (notifys var) ((c, f) : n) return $ Notify c (notifys var)
remNotify :: Notify -> IO () remNotify notify = do n <- readIORef (notifys notify) writeIORef (notifys notify) (filter (\x -> fst x /= notifyId notify) n)
Object layering
textBox-text -< "test" filename <- newVar Nothing addNotify filename hatCover lbl-text =< with filename $ \x -> case x of Nothing -> "Select a file" Just x -> "Loaded: " ++ x
where
(-) :: GtkObject -> GtkProp -> Var a -- ignoring lots of details here (-<) :: Var a -> a -> IO () (=<) :: Var a -> Action a -> IO ()
with :: Var a -> (a -> b) -> Action b