PropLang: Difference between revisions

Latest revision as of 21:21, 23 June 2007

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, some patches from Joachim Breitner, discussions and help from Duncan Coutts

For a darcs repo see: http://www.cs.york.ac.uk/fp/darcs/proplang/

In particular check out Sample.hs, I am particularly proud of the word count:

sb!text =< with1 (txt!text) (\x ->
    "Word count: " ++ show (length $ words x))

Overview

There are events, you can register to be notified when an event fires by doing

event += handler

There are variables, which have events which fire, and a value which you can set and get.

variable <- newVar "value"
variable += handler
variable -< "value"
x <- getVal variable

There are objects, objects have properties. A property is just a variable.

window!text += handler
window!text -< "Titlebar text"

There are bindings which relate variables.

-- the window text is the variable
window!text =<= variable
-- the window text is the variable, but upppercase
window!text =< with1 variable (map toUpper)
-- combine the two texts to create the window text
window!text =< with2 variable1 variable2 (++)

If any of the values on the RHS of a binding change, then the LHS is updated.

@@ Line 1: / Line 1: @@
+[[Category:User interfaces]] [[Category:Proposals]] [[Category:Libraries]]
 A design for a GUI library which is more like Haskell and less like C. To be written over Gtk2Hs.
@@ Line 5: / Line 6: @@
 == Thoughts by ==
-Neil Mitchell, Duncan Coutts
+Neil Mitchell, some patches from Joachim Breitner, discussions and help from Duncan Coutts
-== The Var concept ==
+For a darcs repo see: http://www.cs.york.ac.uk/fp/darcs/proplang/
-This is the low level stuff, on which the library will be built
+In particular check out Sample.hs, I am particularly proud of the word count:
-  data Var a = ...
+  sb!text =< with1 (txt!text) (\x ->
- data Notify
+     "Word count: " ++ show (length $ words x))
- get :: Var a -> IO a
+== Overview ==
- set :: Var a -> a -> IO ()
- addNotify :: Var a -> (a -> IO ()) -> IO Notify
- remNotify :: Notify -> IO ()
- newVar :: a -> IO (Var a)
+There are events, you can register to be notified when an event fires by doing
-== Object layering ==
+ event += handler
- textBox-text -< "test"
+There are variables, which have events which fire, and a value which you can set and get.
- filename <- newVar Nothing
- addNotify filename hatCover
- lbl-text =< with filename $ \x ->
-                  case x of
-                      Nothing -> "Select a file"
-                      Just x -> "Loaded: " ++ x
+ variable <- newVar "value"
+ variable += handler
+ variable -< "value"
+ x <- getVal variable
-where
+There are objects, objects have properties. A property is just a variable.
-  (-) :: GtkObject -> GtkProp -> Var a -- ignoring lots of details here
+  window!text += handler
-  (-<) :: Var a -> a -> IO ()
+  window!text -< "Titlebar text"
- (=<) :: Var a -> Action a -> IO ()
-  with :: Var a -> (a -> b) -> Action b
+There are bindings which relate variables.
+  -- the window text is the variable
+ window!text =<= variable
+ -- the window text is the variable, but upppercase
+ window!text =< with1 variable (map toUpper)
+ -- combine the two texts to create the window text
+ window!text =< with2 variable1 variable2 (++)
+If any of the values on the RHS of a binding change, then the LHS is updated.